Sustainable Practices on Aquatic Sciences I

SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Editors Erkan CAN Şafak SEYHANEYILDIZ CAN Lyon 2025 SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Editors Erkan CAN Şafak SEYHANEYILDIZ CAN Lyon 2025 Sustainable Practices on Aquatic Sciences I Editors • Prof. Dr. Erkan CAN • Orcid: 0000-0001-9440-7319 • Assoc. Prof. Dr. Şafak SEYHANEYILDIZ CAN • Orcid: 0000-0003-2297-9742 Cover Design • Motion Graphics Book Layout • Motion Graphics First Published • October 2025, Lyon e-ISBN: 978-2-38236-929-6 DOI: 10.5281/zenodo.17391400 copyright © 2025 by Livre de Lyon All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the Publisher. The author or authors of the relevant section are responsible for any copyright infringement that may occur due to the images and graphics used in the book. The editor or publisher does not assume responsibility in this regard. Publisher • Livre de Lyon Address • 37 rue marietton, 69009, Lyon France website • http://www.livredelyon.com e-mail • [email protected] I PREFACE In recent years, the growing awareness of environmental challenges and the urgent need for sustainable development have driven significant advances in aquatic sciences. This book, Sustainable Practices in Aquatic Sciences, brings together innovative research and cutting-edge applications that aim to harmonize aquatic resource use with ecological preservation. The chapters included span a wide array of topics that collectively offer a comprehensive perspective on sustainability in marine and freshwater environments. Starting with the exploration of novel marine-derived biomaterials from tunicates and the role of nanotechnology in aquaculture, the book delves into biodiversity and waste upcycling with a focus on marine malacostraca in Türkiye. Further sections examine crucial topics such as reducing sodium chloride in processed seafood, the potential of cellular aquaculture to mitigate disease risks, and advancements in fish breeding for inland aquaculture. Additionally, the book addresses natural therapeutic agents like propolis for fish health, the role of freshwater snails in sustainable wastewater treatment, and the importance of seafood in functional food production. It also explores the complexities of sex control in aquaculture and concludes with an insightful discussion on transitioning from plastic to bioplastic through the use of algae, paving the way for a more sustainable aquatic future. This collection serves as a vital resource for researchers, practitioners, and policymakers committed to advancing sustainable aquatic sciences and fostering an eco-friendly future. Editors Prof. Dr. Erkan Can Assoc. Prof. Dr. Şafak Seyhaneyıldız Can III CONTENTS PREFACE I CHAPTER I. SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED BIOMATERIALS AND METHODS FOR AN ECO-FRIENDLY FUTURE 1 Sinem AYDIN CHAPTER II. NANOTECHNOLOGY IN AQUACULTURE: INNOVATIONS, 49 APPLICATOINS AND FUTURE PERSPECTIVES FOR SUSTAINABILITY OLENA HONCHAROVA & SABRINE BOUCETTA & MUSTAFA DOĞAN & DENİZ ÇİRA & ERKAN CAN CHAPTER III. MARINE MALACOSTRACA IN TÜRKİYE: A COMPREHENSIVE REVIEW ON BIODIVERSITY AND WASTE UPCYCLING 77 Özge Özgen CHAPTER IV. CAN CELLULAR AQUACULTURE ELIMINATE CURRENT DISEASE RISKS IN AQUACULTURE? 97 Ulviye KARACALAR CHAPTER V. FISH BREEDING IN INLAND AQUACULTURE 105 Bilge KARAHAN & Sevim HAMZAÇEBİ CHAPTER VI. PROPOLIS AS A NATURAL THERAPEUTIC IN SUSTAINABLE AQUACULTURE: CURRENT AND FUTURE PERSPECTIVES ON FISH HEALTH 119 Deniz ÇİRA & Erkan CAN CHAPTER VII. THE ROLE OF FRESHWATER SNAILS IN ADVANCING SUSTAINABLE WASTEWATER TREATMENT: A NATURAL APPROACH 129 Filiz Kutluyer Kocabaş & Mehmet Kocabaş CHAPTER VIII. THE ROLE OF SEAFOOD IN SUSTAINABLE FUNCTIONAL FOOD PRODUCTION 145 Hatice GÜNDÜZ & Fatma ÖZTÜRK iv   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I CHAPTER IX. SEX CONTROL AND MANIPULATION IN AQUACULTURE 155 Mustafa DOĞAN CHAPTER X. FROM PLASTIC TO BIOPLASTIC: A SUSTAINABLE AQUATIC FUTURE WITH ALGAE 179 Şafak SEYHANEYILDIZ CAN SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   7 spicules (Lambert & Lambert, 1987), or a dense coating of sand grains that may provide camouflage or structural reinforcement (Young, 1989). Appendicularians represent another distinct group within the subphylum Tunicata. Although molecular phylogenetic analyses based on 18S rDNA sequences suggest that appendicularians share a common ancestor with other tunicate groups (e.g., Ascidiacea and Thaliacea). They exhibit several distinct morphological characteristics. Notably, unlike other tunicates, appendicularians lack a tunic, the characteristic integumentary tissue composed of tunicin that gives the subphylum its name. Instead, appendicularians produce a balloon-like, gelatinous structure known as a “house”, which serves as a specialized feeding apparatus, facilitating the capture and filtration of suspended particles from the surrounding water (Kimura & Itoh, 2001). The tunic of tunicates can be classified into two types based on its composition: rigid and soft. These types vary depending on the species of tunicate. Tunicates are categorized as either gelatinous (soft, such as Molgula manhattensis) or leathery (tough, like Styela clava). This classification affects their habitat preferences, predation risks, and efficiency in absorbing food, gases, and pollutants (Rosner & Rinkevich, 2024). Certain ascidian taxa, particularly within the families Didemnidae, Polyclinidae, and Pyuridae (Aplousobranchia), possess calcareous spicules composed of calcium carbonate embedded within their internal tissues, most notably within the tunic of colonial forms (Monniot et al., 1995). In many didemnid ascidians, these spicules are abundant and well-developed. Given that the morphology and size range of spicules are species-specific, they are frequently utilized as key diagnostic characters in ascidian taxonomy (Hirose et al., 2010). 2.2. Biology of tunicates Tunicates are an evolutionarily important group of cosmopolitan marine, sessile, filter-feeding animals belonging to the subphylum Tunicata (or Urochordata), a phylum within the Chordata. In their phylogenetic relationship, they are the closest living invertebrate relatives of vertebrates, possessing key vertebrate-like features, complex organs, and a diverse array of cell types. They serve as valuable model organisms in various scientific fields such as developmental and evolutionary studies (Anselmi et al., 2025; Johnson et al., 2024; Todorov et al., 2024), the immune system, embryogenesis (Bauermeister et al., 2019), regeneration, stem cell biology (Tiozzo et al., 2008; Vanni et al., 2022), and bioactive compounds (Cooreman et al., 2023; Ramesh et al., 8   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I 2021) and the production of secondary metabolites, some of which may have pharmaceutical potential (Gao et al., 2023), biological invasion (Zhan et al., 2015), allorecognition (Nydam et al., 2021), germ cell sequestration (Kassmer et al., 2016), cell fate determination (Fujii et al., 2021). These features not only make them biologically fascinating but also provide them with qualities and functions suitable for sustainable applications. Ascidians are classified as chordates due to their short-lived (12-24 h) swimming larval stage, which exhibits key chordate features, including a notochord, dorsal tubular nerve cord, and pharyngeal gill slits. These structures are lost during metamorphosis, when the larvae settle, absorb their tails, and transform into sessile juveniles. The adult ascidian has a sac-like body with two siphons: the oral siphon, which draws water in, and the atrial siphon, which expels filtered water. The body of an adult ascidian, or each zooid in colonial ascidians, contains several distinct organ systems. In addition to the outer tunic and reproductive organs, key internal structures include a branchial sac that occupies a significant portion of the trunk, a digestive system comprising the pharynx, stomach, and gut, a tubular heart, and an open circulatory system containing hemolymph with various blood cell types (Figure 3). Figure 3. Illustration of a solitary ascidian (left) and a colonial ascidian (right) in ventral view. Vanni et al. (2022) via the Creative Commons Attribution 4.0 International Public License https://creativecommons.org/licenses/by/4.0/ legalcode (accessed on 13 October 2025). SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   9 2.3. The nervous system Ascidians possess a well-organized nervous system comprising peripheral nerve cells and a central neural tube, which includes the sensory vesicle, neck, visceral or tail ganglion, and caudal nerve cord. A prominent ganglion is situated within the connective tissue between the oral and atrial siphons, adjacent to an exocrine gland. Additional structural features include segmented muscle bands and a continuous epidermal layer enclosing the body. In colonial species, individual zooids are interconnected via blood vessels, facilitating physiological coordination across the colony (Rosner & Rinkevich, 2024). Appendicularia, ascidians, and some thaliaceans have a tadpole-like larva with a notochord, which metamorphoses into sessile adults, particularly in the case of ascidians (Lemaire & Piette, 2015). 2.4. The circulatory system Tunicates possess an open circulatory system, characterized by few distinct blood vessels. The heart is a simple tubular structure that propels blood through peristaltic contractions. The heart consists of two tubes, the pericardium and the myocardium (Brunetti & Mastrototaro, 2017). The tunicate heart periodically reverses the direction of blood flow after approximately 100 beats in one direction, pausing briefly before contracting in the opposite direction (Shimek, 2008). Thaliaceans possess a closed circulatory system with a tubular heart that periodically reverses the direction of blood flow, enhancing the distribution of nutrients and gases throughout the body (Lemaire & Piette, 2015). 2.5. The respiration system The branchial sac (also known as the branchial basket) functions both in respiration and the filtration of food particles. Gas exchange primarily occurs across the gill slits, but it is also facilitated through additional body surfaces, including the lining of the atrium. The branchial sac plays a central role in filtration and bioaccumulation. Its walls are perforated by numerous stigmata and lined with ciliated epithelium. Ciliary movement generates a continuous flow of water from the oral siphon through the branchial sac, allowing for the efficient filtration of seawater. This process is vital for respiration, as it captures suspended particulate matter and directs it toward the esophagus for further processing. Located on the ventral side of the branchial sac, the endostyle is a ciliated groove that secretes mucus essential for trapping suspended particles. It is 10   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I considered homologous to the vertebrate thyroid gland, although its function differs significantly. The branchial sac also contains various hemocytes, including granular amoebocytes that express immune-related genes such as tumor necrosis factor (TNF-α) and complement component C3, as well as stem cells. Additionally, the morphology of the branchial sac serves as a key taxonomic feature distinguishing the three orders within the class Ascidiacea: Aplousobranchia, characterized by a simple branchial sac; Phlebobranchia, possessing longitudinal blood vessels; and Stolidobranchia, which exhibit a folded branchial sac (Shenkar & Swalla, 2011). Appendicularians lack specialized respiratory structures; gas exchange occurs primarily via diffusion across the thin, permeable body surface, aided by continuous water flow through the mucous house. Gas exchange primarily occurs across the numerous gill slits of the branchial sac, as well as other thin, vascularized body surfaces, such as the atrial lining, facilitating efficient oxygen uptake and carbon dioxide removal. 2.6. Digestive and excretory systems The excretory system of tunicates is relatively simple and closely integrated with their feeding and circulatory systems. Water enters the body through the incurrent siphon and passes through the branchial basket via modified gill slits, then flows into the atrium before exiting through the excurrent (atrial) siphon. The atrium also serves as a common cavity where gametes and fecal matter accumulate, both of which are expelled through the atrial siphon (Shimek, 2008). Sea water is driven through the gill slits into the branchial basket by cilia lining its surface. Within the basket, a ventral groove known as the endostyle secretes mucus that forms a sheet lining the interior of the basket. Particulate organic matter entering through the incurrent siphon becomes trapped in this mucus. Ciliary action then transports the mucus, now containing food particles, to a dorsal food groove, which directs it to the mouth. The food-laden mucus passes through the esophagus into the stomach for digestion. Undigested material moves into the intestine and is ultimately expelled through the anus. Fecal matter accumulates in the atrium and is flushed out via the excurrent siphon with outgoing water (Shimek, 2008). This efficient filter-feeding mechanism contributes to the ecological success and invasiveness of many tunicate species (Figure 4). SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   11 Figure 4. The water circulation within a Ciona robusta – red dots signify larger particles, while green dots are smaller ones. Valsesia et al. (2021) via Creative Commons (https://creativecommons.org/licenses/by/4.0), adapted by N. Hanacek/NIST. In appendicularians, the mucus structure, used for feeding, is actively maintained and pumped within water containing suspended particles. This structure functions as a highly efficient filtration apparatus, wherein food particles are selectively trapped and directed toward the oral opening for ingestion. The gut includes a dorsal esophagus, a bilobed saccular stomach, and a curved intestine, divided into vertical, mid-, and distal intestine (or rectum) (Burighel et al., 2001). The feeding mechanism in appendicularians is distinct from that of other tunicates. Specialized glands on the surface of the body secrete a complex mucous structure, commonly referred to as a “house,” which envelops the animal. Rhythmic undulations of the tail generate a feeding current that draws water into the house and passes it through a finely woven mucous mesh. This mucous sheet functions as an effective filtration net, capturing suspended food particles from the surrounding water for ingestion. The digestive tract in thaliaceans includes the pharynx, esophagus, stomach, intestine, and anus. This system efficiently processes suspended particles filtered from the water column. 12   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I 2.7. Life cycle and reproduction Tunicates exhibit diverse reproductive strategies, including both asexual budding and sexual reproduction. Most tunicates are primarily hermaphroditic, possessing both male and female reproductive organs, which enables reproduction through both sexual and asexual means, thereby facilitating rapid population expansion. They can often self-fertilize or cross-fertilize and can also produce new individuals through a process known as asexual reproduction, also referred to as budding. They are releasing eggs and sperm into the water column for external fertilization. Others brood their offspring internally. In solitary ascidians, reproduction predominantly occurs sexually, whereas colonial ascidians are capable of both sexual reproduction and asexual reproduction via budding (vegetative reproduction) and strobilation, with an extended capacity of regeneration. Most solitary ascidians are hermaphroditic and reproduce via external fertilization, and while the larval phase is absent or very reduced in the planktonic forms, the benthic adult ascidians present a planktonic stage in which the larva resembles a free-swimming tadpole that exhibits a brief pelagic phase, with an ovate trunk and an elongated tail, responsible for dispersal (Lambert, 2005a). During this stage, the larvae actively disperse and then settle onto a wide range of substrates. Upon settlement, they undergo metamorphosis and transition into sessile adult forms (Hong et al., 2025; Shenkar & Swalla, 2011). Notably, hermaphroditic ascidians exhibit self-incompatibility (SI) mechanisms at fertilization, which prevent self-fertilization and promote genetic diversity (Nonaka & Satake, 2010). In contrast, appendicularians, another tunicate group with a cosmopolitan distribution, possess separate sexes and reproduce exclusively through sexual reproduction, a trait considered atypical among tunicates. The asexual reproductive capacity observed in many tunicate species is also hypothesized to contribute to their regenerative abilities, potentially allowing for the replacement or regrowth of body parts through budding mechanisms (Holland, 2016). Ascidians, or sea squirts, typically exhibit a biphasic life cycle comprising a free-swimming larval stage and a sessile adult phase. The larval form, which resembles a tadpole, possesses a notochord, a key diagnostic feature of the phylum Chordata that facilitates active dispersal. This dual-phase lifestyle enhances ecological plasticity and supports the rapid colonization of suitable substrates in marine environments. Life span among ascidian species varies considerably, generally ranging from approximately two months to one year SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   13 (Shenkar & Swalla, 2011). The solitary species reproduce through external fertilization as broadcast spawners, while colonial species are typically ovoviviparous (Gasparini & Ballarin, 2018). Tunicate larvae bear a striking resemblance to the tadpole larvae of other chordates, possessing key features such as a notochord and a post-anal tail. It has several sensory systems, including the ocellus and otolith, which are sensitive to light and gravity, respectively. However, following retrogressive metamorphosis, these structures are lost, resulting in a sessile adult form devoid of typical chordate characteristics. Due to this transitional morphology, tunicates are often regarded as an “evolutionary connecting link” between invertebrates and vertebrate chordates (Ramesh et al., 2021). The reproductive periodicity of ascidians varies considerably among species and remains poorly characterized for many taxa. However, it is well established that water temperature plays a key regulatory role in their reproductive cycles (Lambert, 2005a). In temperate regions, ascidian spawning typically peaks during the summer months, followed by a marked decline in reproductive activity as temperatures decrease (Stoner, 1990). Conversely, in tropical and subtropical environments, ascidian populations often exhibit continuous gamete release throughout the year (Goodbody, 1961). Gonads develop on either side of the zooid, with the ovary positioned posterior to the testis. During reproduction, the ovulated egg is released into a sac-like brood pouch, which is formed as an outgrowth of the body wall, where internal fertilization occurs. Embryonic development occurs within this pouch, and gestation typically lasts more than one month. Metamorphosis begins shortly after larval release, during which two buds form on the right side of the oozoid and one on the left. Individuals of the same generation tend to develop and senesce synchronously. Notably, sexual reproduction does not interfere with asexual reproduction, which occurs via self-division or budding. This process results in colonies of genetically identical zooids (Rodriguez et al., 2017). 3. Tunicates in Marine Ecosystems 3.1. Ecological role of tunicates Tunicates play a crucial ecological role, contributing to the stability of marine ecosystems through their filter-feeding behavior, which is vital in nutrient cycling and maintaining water quality (Bone et al., 2003; Piri et al., 2022). 14   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Ascidians are benthic and pelagic filter feeders; they’re commonly called sea squirts and derive their name from their ability to contract and expel water through siphons upon contact. Sea water enters the pharynx through an oral siphon (branchial, inhalant, incurrent siphon), which is typically moved by ciliary beating. Food particles are trapped on a mucous net secreted by the endostyle, while water and waste exit the body through an atrial siphon or exhalant (excurrent siphon) (Petersen, 2007). Tunicates play a critical role in marine biogeochemical cycles through their unique feeding and waste production mechanisms. By producing mucusrich organic matter, fecal pellets, and trapping themselves within sinking particulate organic matter, tunicates contribute significantly to vertical carbon fluxes, transporting organic carbon and associated minerals from surface waters to the deep ocean (Ramesh et al., 2021). Their filtration capacity enables them to remove large volumes of suspended particles from the water column, thereby enhancing water clarity, influencing nutrient dynamics, and controlling plankton populations. In addition to their role in nutrient cycling, tunicates play a crucial part in the marine food web by transferring energy to various compartments, serving as prey for various fish and invertebrate species (Luo et al., 2022). Photosymbiosis has been documented in several colonial ascidians of the family Didemnidae, predominantly inhabiting tropical and subtropical marine environments. These ascidians host cyanobacterial symbionts, primarily species of Prochloron and Synechocystis. Approximately 30 species across four didemnid genera have been described as hosts to these photosymbionts. While many of these ascidian species maintain obligate symbioses, consistently harboring specific cyanobacterial partners, others engage in facultative associations, where the presence of photosymbionts is occasional or environmentally dependent (Su et al., 2013). Some tunicate species also exhibit obligate photosymbiosis and have been proposed as potential bioindicators of environmental stress, providing insight into the health of marine ecosystems. Despite these known ecological functions, the roles of certain tunicate-derived marine natural products (MNPs) remain poorly understood, and further research is necessary to elucidate their ecological and functional significance (Ramesh et al., 2021). Ascidians represent a crucial component of marine benthic communities and are also recognized as significant contributors to marine biofouling, particularly through their colonization of artificial substrates such as ship hulls, buoys, and SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   15 fishing nets. Despite extensive research on the chemical cues mediating larval settlement and metamorphosis in ascidians, the role of physical environmental factors in these processes remains relatively underexplored. To date, only a limited number of studies have investigated the influence of physical parameters on the behavior and developmental transitions of ascidian larvae, underscoring the need for further research in this area (Feng et al., 2010). Tunicates are sciaphilous species (Brunetti & Mastrototaro, 2017). Light is widely recognized as an important environmental cue influencing the settlement behavior of tadpole larvae in many ascidian species (Svane & Young, 1989). Numerous species exhibit photonegative behavior during settlement, a trait believed to facilitate their preferential colonization of cryptic or shaded habitats (Manríquez & Castilla, 2007). In addition to light, water temperature has been identified as a key environmental factor influencing the distribution and occurrence of ascidian populations (Lambert, 2005b). Water salinity is a critical abiotic factor that significantly influences both the development and distribution of ascidian species. Variations in salinity can affect larval settlement, growth rates, reproductive success, and overall physiological tolerance, thereby shaping their ecological niches and biogeographic patterns (Nagar & Shenkar, 2016). Furthermore, the physical characteristics of the substratum, including its lithological properties, have been shown to affect larval settlement. For example, Groppelli et al. (2003) demonstrated that the mineral composition of the substratum significantly influences the settlement of Phallusia mammillata larvae, suggesting that substratum composition may play a regulatory role in the spatial distribution of tunicate communities. Ascidians are sessile marine invertebrates belonging to the subphylum Tunicata and are considered the closest living relatives of vertebrates within the phylum Chordata. They have garnered considerable scientific interest for their utility in addressing complex biological processes, particularly in the fields of developmental biology and immune system evolution. As holobionts, ascidians maintain intricate associations with diverse microbial communities, which play a key role in enhancing host adaptability to varying environmental conditions. This symbiotic relationship contributes to their ecological success, enabling ascidians to act as both dominant components of benthic communities and effective marine invaders. As filter feeders, ascidians are continuously exposed to environmental microorganisms, including potential pathogens, necessitating a highly responsive and organized immune system. The tunic, a metabolically active 16   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I outer tissue composed primarily of a cellulosic matrix, serves as the first line of defense against both pathogens and predators. Internally, the oral siphon and pharynx play central roles in immunological surveillance, functioning as primary immune organs that can detect foreign material and initiate appropriate immune responses (Bauermeister et al., 2019). In contrast, the introduction of non-native ascidian species has been linked to negative ecological impacts, particularly within benthic communities where they often outcompete native species. Additionally, invasive ascidians pose a threat to the aquaculture industry by fouling infrastructure and reducing productivity (Topić Popović et al., 2025). Adult ascidians exhibit a significant reduction in chordate features, with their bodies encased in a protective outer tunic composed of a unique celluloselike polysaccharide known as tunicin. This extracellular matrix often contains vacuolated cells that may store sulfuric acid, potentially serving as a defense mechanism against predation. Additionally, several ascidian species demonstrate the ability to bioaccumulate trace metals such as vanadium, chromium, and molybdenum within specialized vanadocytes or other hemolymphatic cells, a phenomenon that remains of interest in both ecotoxicology and marine biochemistry (Bauermeister et al., 2019; Goodbody, 1974). 3.2. Habitat and global distribution Tunicates appear to have undergone particularly rapid evolutionary diversification, remaining restricted to exclusively marine environments while radiating to occupy a broad range of habitats. Most ascidian species are ecologically significant benthic organisms, predominantly inhabiting shallow coastal waters and substrates. However, tunicates as a whole are found across diverse marine environments, including pelagic zones of the open ocean and deep-sea habitats, demonstrating their extensive ecological adaptability (Shenkar & Swalla, 2011). Tunicates are exclusively marine organisms, exhibiting an inability to survive in environments with low salinity. They are widely distributed across diverse marine habitats, ranging from tropical to polar regions. These organisms inhabit a variety of ecological niches, including shallow coastal zones, the open ocean, and depths extending from the intertidal zone to hadal depths (Holland, 2016). They are cosmopolitan and commonly found in coastal waters and coral reefs, inhabiting the littoral zone, which extends from the intertidal to the subtidal zones, where they attach to rocks, shells, seaweeds, mangrove roots, SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   23 inhibition. Botrylloides niger, an alien ascidian species, represents a promising source of bioactive compounds likely developed for ecological adaptation and competition. It is notably rich in diverse lipid species beneficial to human health, including polyunsaturated fatty acids (PUFAs) that are uncommon in most foods. These biochemical properties highlight its potential to transition from an ecological threat to a valuable and accessible bioresource. Consequently, B. niger and other invasive ascidians may offer significant economic potential, particularly in the food and pharmaceutical sectors, through the development of functional products derived from these organisms. (Hassanzadeh, 2014). The lipid profile of ascidians has been found to resemble that of fish oil (Hassanzadeh, 2014), suggesting their potential as alternative sources of marine lipids for aquaculture. Additionally, their amino acid composition is comparable to egg albumin, further supporting their use as a high-quality feed ingredient. Combined with their high protein content and low caloric value. Ascidians represent a valuable and underutilized source of marine-derived nutrition (Hassanzadeh, 2014). Despite these benefits, the consumption of aquatic products in some countries remains significantly lower than the global average. Consequently, aquatic products represent a critical component of a balanced and healthy diet and should be better utilized and promoted. Increasing public awareness about the nutritional and sensory qualities of seafood can encourage greater consumption over time. Ascidians serve as a crucial food source for a range of marine predators, including fish, sea stars, and specific crab species. Additionally, some ascidian species, such as Halocynthia roretzi and Styela clava, are consumed by humans (Gao et al., 2023; Lambert et al., 2016). In recent decades, ascidians have garnered increasing interest as potential alternative food sources due to their high nutritional value, which includes proteins, amino acids, lipids, and bioactive secondary metabolites (Palanisamy et al., 2017). Moreover, ascidians are recognized as a rich source of diverse bioactive chemical compounds, including peptides, alkaloids, polyethers, macrolides, terpenes, and polysulfides (Palanisamy et al., 2017). In addition to their chemical potential, ascidians are increasingly being utilized as model organisms in various fields of biological research, including immunobiology, allorecognition, angiogenesis, and whole-body regeneration. Their remarkable regenerative abilities have garnered significant attention in the fields of regenerative medicine and ageing research (Della Sala et al., 2022). 24   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I 4.2. Cellulose content (tunicate cellulose = highly crystalline nanocellulose) Tunicates have a gelatinous outer “tunic” composed primarily of celluloselike compounds, including tunicin. This natural polymer shares structural similarities with plant cellulose (with longer polymer chains) but is biologically derived, making it a unique and renewable resource for material applications. The tunic, a key component of the tunicate’s defense mechanism, offers both durability and flexibility, enabling tunicates to thrive in a wide range of marine environments. This remarkable combination of strength and biodegradability positions as a compelling alternative to synthetic, petroleum-based materials (Jiang et al., 2023). 5. Threats to Tunicate Populations 5.1. Climate change effects (temperature, ocean acidification) Climate change poses a significant threat to tunicate populations through rising sea temperatures, ocean acidification, and shifting oceanographic conditions. Elevated temperatures can alter metabolic rates, reproductive cycles, and larval development in tunicates, potentially leading to population declines or shifts in distribution. Ocean acidification, caused by increased CO₂ absorption, may also affect the structural integrity of tunicate tunics and disrupt microbial symbioses essential for nutrient cycling. Moreover, changes in current patterns and salinity can impact larval dispersal and settlement, further influencing population dynamics (Gallo et al., 2019). 5.2. Pollution and its impact on marine biodiversity Tunicates are highly susceptible to pollutants due to their filter-feeding behavior and sedentary lifestyle. They can accumulate a wide range of contaminants, including heavy metals, microplastics, polycyclic aromatic hydrocarbons (PAHs), and chlorinated compounds, such as tributyltin (TBT) and copper, both of which are components of marine antifouling paints. This not only affects their own physiology but also poses a risk to the broader marine food web. The degradation of tunicate habitats through chemical pollution and nutrient overloading can lead to a decline in biodiversity, particularly among species that rely on tunicates as shelter or food. Long-term exposure to pollutants may also alter species composition within tunicate communities, favoring more tolerant invasive or opportunistic species over native biodiversity (Radford et al., 2000). SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   25 5.3. Invasive Species and Habitat Competition Bioinvasions pose serious threats to marine biodiversity and ecosystem services, with marine non-indigenous species (NIS), particularly invasive species, imposing substantial ecological and economic costs globally. These impacts extend beyond direct market losses to include damage to biodiversity, public health, and nonmarket environmental assets. Marine biological invasions are primarily driven by global shipping activities, particularly through the discharge of ballast water and biofouling on vessel surfaces. However, most NIS risk assessments have focused predominantly on ballast water, emphasizing three stages: uptake, survival during transit, and discharge. Given limited management resources, it is increasingly recommended that high-risk invasive species be prioritized for targeted intervention and control. (Andersen, et al., 2004). Ascidians are widely regarded as a model taxon for studying biological invasions due to their prominent presence in reports of bioinvasions. They represent one of the most active groups in such studies and have successfully invaded coastal regions across all continents except Antarctica, spanning from the northern to the southern hemisphere. Solitary ascidians typically inhabit deeper and more stable habitats, including rocky substrates, coral reefs, and submerged artificial structures. In contrast, colonial ascidians are predominantly found in more dynamic and shallow environments such as coastal zones, estuaries, shallow reefs, and rocky shorelines. This broad ecological distribution allows both solitary and colonial ascidians to fulfill important functional roles within marine ecosystems. However, when introduced to non-native regions primarily via human-mediated vectors such as shipping and aquaculture, they can become invasive species, posing threats to native biodiversity and ecosystem stability (Rosner & Rinkevich, 2024; Shenkar & Swalla, 2011). The abundance, accessibility, and filter-feeding behavior of ascidians, characterized by their reproductive strategy of simultaneously releasing large quantities of gametes and undergoing rapid larval development, along with their high sensitivity to a wide range of toxins, make them particularly responsive to environmental fluctuations. This pronounced sensitivity positions ascidians as valuable bioindicators for assessing environmental health, rendering them well-suited for investigating the impacts of pollutants and stressors on marine ecosystems. Additionally, their adaptability to unstable and variable environmental conditions, alongside the highly invasive nature of certain species, positions ascidians as excellent model organisms for studying species 26   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I invasions and biodiversity dynamics (Corbo et al., 2001; Rosner & Rinkevich, 2024). As omnivorous filter feeders with rapid growth and reproduction rates, tunicates aggressively compete for habitat and food resources. Their relatively simple feeding strategy, combined with effective anti-predator defenses, enables them to spread readily and rapidly colonize available surfaces. Because of these traits, tunicates pose a significant ecological threat as invasive species (Topić Popović et al., 2025). Ascidians are conspicuous invasive species in both tropical and temperate waters (Rocha et al., 2012). They are known to be strong competitors. These traits make ascidians highly successful invaders that can create major economic expenses by heavily fouling marine vessels and man-made structures, as well as by overgrowing aquaculture equipment and organisms (Aldred & Clare, 2014). Tunicates exhibit a highly efficient and generalized filter-feeding strategy that allows them to exploit a wide range of particle sizes, resulting in direct competition with native filter-feeding species in invaded ecosystems. Their success as invaders is further facilitated by the absence or scarcity of natural predators in non-native environments, coupled with a remarkable tolerance to a broad range of environmental conditions, including fluctuations in salinity and temperature. Although the natural dispersal potential of benthic tunicates is constrained by a short-lived larval stage, typically lasting only a few hours to several days, their high reproductive capacity and survival rates enable them to colonize rapidly. When combined with anthropogenic vectors such as global shipping, aquaculture operations, aquariums, Lessepsian migrants via Suez and Gibraltar Canals (e.g., rabbitfish), and ballast water and hull fouling, the fouling of artificial structures significantly enhances their capacity for long-distance dispersal and establishment in new habitats, contributing to their widespread invasive success (Hong et al., 2025). 6. Tunicates: Applications in Sustainable Materials 6.1. Nanocellulose and biopolymers of tunicates Tunicate-derived nanocellulose exhibits exceptional properties, including high mechanical strength, remarkable purity, and an elevated Young’s modulus. Additionally, it possesses unique optical, electrical, magneto-mechanical, and rheological characteristics, making it highly versatile material for advanced applications (Lv et al., 2023). SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   27 Additionally, tunicate cellulose can be processed into nanocellulose, a high-performance biomaterial with a wide range of potential applications. These applications demonstrate significant promise in both food technology and materials science (Gao et al., 2032; Zhao et al., 2015). Figure 5. Application of tunicate cellulose in different fields. Drug delivery by Public Domain is licenced under CC BY-SA 4.0, wound healing by Raquel Baranow, environmental sustainability by Alexander Klepnev, and electronics by Yei Hwan Jung et al. (2015) are licenced under CC BY-4.0, and paper manufacture by KOchstudiO is licenced under CC BY-SA 3.0. (https://creativecommons.org/licenses/). Cellulose extracted from the outer capsule of tunicates has garnered significant attention from researchers due to its excellent physicochemical properties. In addition, its nanocellulose exhibits high strength, purity, modulus, and versatile photoelectromagnetic properties, and is gradually becoming a novel biomaterial. However, the utilization of tunicates is extremely low, and their discarded outer capsules accumulate in large quantities, resulting in a significant environmental burden and waste of resources. Therefore, it has become imperative to fully exploit and reuse tunicates. Among these, ascidians are the most extensively researched for sustainable material applications due to their high nanocellulose content and stationary lifestyle, which facilitates aquaculture and harvesting (Lv et al., 2023). The 28   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I applications of tunicate and its composites in various fields (e.g., biomedical field, energy and electronics, polymer reinforcement, food packaging field, paper industry and environmental materials, luminescent fibers, high-strength composites, biodegradable sensors, bone tissue engineering, wound healing, food industry, polymer reinforced materials, paper manufacture, energy and electronics, environmental protection material, drug delivery, myocardial tissue engineering etc.) are also discussed (Figure 5) (Lv et al., 2023). The upcycling of ascidians into nanocellulose networks presents an innovative approach to ecosystem preservation and resource valorization, with potential applications in managing both native and invasive ascidian species. This strategy introduces a novel, animal-derived class of cellulosic nanonetworks, offering a sustainable platform for the development of advanced biomaterials within the framework of a coastal blue bioeconomy. Beyond the introduction of these unique nanocellulosics, the valorization of ascidian biomass supports the expansion of integrated biorefineries in coastal regions. These biorefineries may operate through the controlled cultivation of native species or through the ecological management of invasive populations. In both cases, the extraction and utilization of tunicate-derived nanocellulose enable circular and regenerative production models. The ease with which highperformance materials can be derived from ascidian biomass underscores their considerable potential to contribute to the global bioeconomy, particularly in the context of sustainable coastal development and marine resource management (Govindharaj et al., 2025). Tunicates are also novel biomedical substances in the field of tissue engineering, wound dressing, and drug delivery systems (Seddiqi et al., 2021). The use of nanocellulose fibre in the textile manufacturing sector has the potential to mitigate the environmental consequences associated with the industry by utilizing sustainable resources and reducing waste (Cho et al., 2019). 6.2. Biodegradable plastics and sustainable polymer alternatives Ascidians produce a unique extracellular matrix known as the tunic, which contains tunicin, a cellulose-like biopolymer. This natural polymer exhibits biodegradability and renewable characteristics, making it a promising candidate for the development of biodegradable plastics and sustainable polymer alternatives. Utilizing ascidian-derived tunicin could reduce reliance on petroleum-based plastics, thereby contributing to environmentally friendly materials with lower ecological footprints (Hong et al., 2025; Kononova et al., 2022; Zhao & Li, 2014). SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   29 6.3. Biomedical applications of tunicates Ascidians harbour a great microbial community (including bacteria, actinobacteria, cyanobacteria, and fungi. The unique chemical class of ascidians’ antimicrobial metabolites, including sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and other aromatic derivatives, as well as their antimicrobial effects, undoubtedly could provide lead candidates for drug discovery programs in the anti-infective area of interest (Casertano et al., 2020). Tunicates contain remarkable compounds and are a rich source of valuable marine natural products (MNPs) for potential pharmaceutical applications (Palanisamy et al., 2017). The biocompatibility and bioactivity of materials derived from tunicates make them excellent candidates for medical applications. Their low immunogenicity and natural origin facilitate their integration into human tissues and biological systems. To date, more than 1000 chemical structures isolated from these organisms have been described (Carroll et al., 2019). Over 70% of these are alkaloids, including indole alkaloids, followed by pyrocridine, beta-carboline, and indolocarbazole (staurosporine). Several alkaloids contained in tunicates have been shown to have anti-cancer properties. Another interesting class of molecules they contain is peptides. Tunicates are also a rich source of compounds with antibacterial, antifungal, antidiabetic, anti-inflammatory, antiprotozoal, antitumoral, antiviral, anti-cancer, and immunosuppressive activities (Bauermeister et al., 2019; Miranda, 2023). Moreover, natural products (NPs) derived from ascidians have contributed to the development of promising pharmaceuticals, including marketed drugs for the treatment of specific cancers, such as Ecteinascidin 743 or Trabectedin (Yondelis®) from Ecteinascidia turbinata Herdman, 1880, and the peptide dehydrodidemnin B or Plitidepsin (Aplidin®) from Aplidium albicans (Milne Edwards, 1841) (Ramesh et al., 2021). Numerous compounds derived from ascidians have demonstrated significant therapeutic potential, particularly as anti-cancer and anti-viral agents. Notable examples include Didemnins, Aplidine, Trabectedin, and Palmerolide. For instance, Palmerolide, isolated from the Antarctic tunicate Synoicum adareanum, has shown promising efficacy against melanoma, a highly aggressive form of skin cancer (Avalon et al., 2021). Another biologically active molecule, the relaxin hormone, has been identified in the ovarian cells of tunicates such as Ciona intestinalis and is noted 30   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I for its potential to enhance sperm motility. Additionally, marine invertebrates, including ascidians such as Styela plicata, are sources of sulfated polysaccharides, including sulfated fucans and galactans. These compounds, along with highly sulfated polysaccharides like heparin, known for its antithrombin (AT) activity, have been utilized in the treatment of arterial thrombosis (Hassanzadeh, 2011). With over 1,000 isolated bioactive compounds and a wide range of reported applications (Chen et al., 2019), tunicates represent a promising source of marine natural products (MNPs) with significant pharmaceutical potential. These compounds have demonstrated diverse biological activities, including antitumoral, antiviral, antifungal, anti-inflammatory, and antibacterial properties (Palanisamy et al., 2017). Recent studies have identified a variety of tunicate-associated bacteria, including Bacillus, Pantoea, Pseudoalteromonas, Salinicola, Streptomyces, Vibrio, and Virgibacillus, as potential producers of antimicrobial compounds, bioactive secondary metabolites, and biosurfactants (Marques et al., 2022). These microbial symbionts contribute to the defensive mechanisms of their tunicate hosts and represent a promising source of novel bioactive agents for pharmaceutical applications (Ramesh et al., 2021). The robust immune defense system of tunicates, combined with their association with symbiotic microorganisms that possess bioactive properties, makes them highly attractive candidates for marine drug discovery. A recent review by Ramesh et al. (2021) emphasized the diversity of microbial symbionts associated with tunicates, including bacteria, actinomycetes, fungi, and cyanobacteria. Among these, actinomycetes, fungi, and bacteria were identified as the predominant groups, many of which exhibit notable cytotoxic and antimicrobial activities. These microbial communities are responsible for the production of a wide array of secondary metabolites, with alkaloids representing a major class of marine natural products (MNPs) derived from tunicate-associated microorganisms. 6.4. Nutritional applications of tunicates Although most tunicate species are not considered edible, several solitary stolidobranchs from the families Styelidae and Pyuridae are either wildharvested or cultured for human consumption. Notable edible species include Boltenia ovifera, Halocynthia aurantium, Halocynthia roretzi, Microcosmus hartmeyeri, Microcosmus sabatieri, Microcosmus vulgaris, Polycarpa pomaria, Pyura chilensis, Pyura pachydermatina, Styela clava, and Styela plicata. SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   31 These species are generally consumed in Asia, Chile, Japan, Korea, and the Mediterranean, in various forms, including raw, cooked, dried, or pickled, depending on regional culinary traditions. Countries are highlighted for their potential role in food security and sustainable aquaculture (Table 1) (Gao et al., 2023; Lambert et al., 2016). Table 1. Wild-harvested and cultured tunicates for human consumption (Lambert et al., 2016). Wild-harvested species Species Common names Where collected Boltenia ovifera (Linnaeus, 1767) Russia Halocynthia aurantium (Pallas, 1787) bee-dahn-mung-geh (Korea) Korea, Russia Microcosmus hartmeyeri Oka, 1906 harutoboya (Japan) Japan Microcosmus sabatieri Roule, 1885 Mediterranean Microcosmus vulgaris Heller, 1877 sea violet Mediterranean Polycarpa pomaria (Savigny, 1816) Mediterranean Pyura chilensis Molina, 1782 piure Chile Pyura pachydermatina (Herdman, 1881) sea tulip New Zealand (historically) Pyura praeputialis (Heller, 1878) cunjevoi Australia (historically), Chile Pyura vittata (Stimpson, 1852) karasuboya (Japan) dohl-mung-geh or kkeun-mung-geh (Korea) Japan, Korea Cultured species (all are also wild-collected) Species Common names Where collected Halocynthia aurantium (Pallas, 1787) sea peach, ice floe tunicate, akaboya (Japan) Japan Halocynthia roretzi (Drasche, 1884) sea pineapple, munggeh or kkoht-munggeh (Korea), hoya or maboya (Japan) Japan, Korea Styela clava Herdman, 1881 mee-duh-duck (Korea) Korea Styela plicata (Lesueur, 1823) o-mahn-doong-yee or o-mahn-dee (Korea) Korea 32   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Additionally, Ciona intestinalis has been developed as a sustainable protein source for use in animal feed formulations (Samuelsen et al., 2022). Overall, these tunicates have been cultivated and consumed as a delicacy in many countries. 6.5. Environmental and Industrial Applications The ecological functions of tunicates, particularly their role as efficient filter feeders, offer promising avenues for environmentally sustainable industrial applications. Tunicates can be used in aquaculture systems to reduce organic waste and improve water quality. Their filter-feeding abilities allow them to function as natural purifiers, reducing the environmental footprint of intensive aquaculture practices (Hong et al., 2025). Certain tunicate species possess the ability to accumulate heavy metals and other contaminants from seawater. This trait makes them potential tools for bioremediation in polluted coastal and marine ecosystems (Aydın-Önen, 2016; Navon et al., 2020; Tamilsevi et al., 2015; Tzafriri-Milo et al., 2019). The tunic of tunicates, primarily made of cellulose-like materials with a high carbon content, offers potential for carbon sequestration. Additionally, this biomass can be transformed into value-added products, such as biochar or advanced carbonbased nanomaterials (Zhao et al., 2015). Recent research is investigating the lipid content of tunicates as a potential feedstock for renewable energy. Although still in the early stages, this area of study indicates possible applications in producing biolubricants and secondgeneration biofuels (Gao et al., 2023; Santhanam, 2025). 6.6. Exploring New Applications Emerging applications of tunicate-derived materials are advancing the frontiers of sustainable technologies and biomedical innovation. Notably, tunicate-derived nanocellulose is being explored for integration into nextgeneration energy storage systems, including high-performance supercapacitors and batteries, due to its unique mechanical strength, high surface area, and electrical tunability (Zhao et al., 2015). Biodegradable electronics (Zhu et al., 2018) and smart packaging features (Zhao & Li, 2014), as well as antimicrobial properties (Casertano et al., 2020; Ramesh et al., 2021), and moisture responsiveness (Lüskow et al., 2024) are being explored (Hong et al., 2025; Lv et al., 2023). Additionally, bioinks for 3D bioprinting (Govindharaj et al., 2022) SUSTAINABLE APPLICATIONS OF TUNICATES: NOVEL MARINE-DERIVED . . .   39 Cooreman, K., De Spiegeleer, B., Van Poucke, C., Vanavermaete, D., Delbare, D., Wynendaele, E., & De Witte, B. (2023). Emerging pharmaceutical therapies of Ascidian-derived natural products and derivatives. 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Controlled release: Nano-carriers release drugs slowly over time, maintaining therapeutic concentrations with fewer administrations (Aklakur et al., 2016). Enhanced penetration: Due to their small size, nanoparticles can cross mucosal barriers and deliver drugs directly to infection sites. (Munawar et al., 2021, Ahmed et al., 2023). Reduced dosage: Targeted delivery allows for lower doses of drugs, reducing side effects and environmental contamination (Fajardo et al., 2022). 3.3. Nano-antimicrobials Metallic nanoparticles, particularly silver (Ag), copper (Cu), and zinc oxide (ZnO), exhibit potent antimicrobial activity against a wide range of aquaculture pathogens. Their mechanisms of action include: i)Generation of reactive oxygen species (ROS) leading to oxidative stress in bacteria (Dawood et al., 2021); ii). Disruption of bacterial cell membranes (De Silva et al., 2021)and iii).Binding to microbial DNA and proteins, inhibiting replication (Vijayaram et al., 2023). 3.3.1. Applications in aquaculture: Aquaculture, a rapidly expanding industry worldwide, faces increasing pressure from infectious diseases, chemical pollution, and the need to maintain sustainable productivity. Exposure of fish to nanoparticles, whether intentional (for therapeutic purposes) or involuntary (via product release), requires a rigorous assessment of their benefits and risks. ZnO-NPs, incorporated into food formulations, have shown improved growth, immunity, and resistance to bacterial infections. However, side effects at high doses, such as oxidative imbalances, have also been observed.(Sherif et al., 2023) AgNPs, on the other hand, can be used at very low concentrations for potent antimicrobial effects, particularly against Aeromonas hydrophila, a major pathogen in aquaculture. However, their accumulation in tissues and their long-term effects on fish health and the food chain raise unresolved questions(Thanigaivel et al., 2021). It therefore becomes essential to adopt an integrated approach, based on green synthesis, environmental safety and therapeutic efficacy, to integrate nanotechnologies into sustainable aquaculture. 56   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I 3.4. Nano-diagnostics and Biosensors Rapid and accurate detection of pathogens is essential for preventing largescale disease outbreaks. Nanotechnology-based biosensors provide sensitive and real-time diagnostic tools for aquaculture health management. Gold nanoparticles (AuNPs) have been used to develop rapid lateral flow assays for detecting fish viruses such as koi herpesvirus (KHV) (Saleh et al., 2012; Saleh et al., 2014). Carbon nanotubes and graphene oxide are being tested as electrochemical biosensors for detecting bacterial toxins and viral particles in aquaculture water (Pires et al., 2020¸ Padmapriya et al., 2024). Magnetic nanoparticles enable pathogen capture and concentration, improving the sensitivity of molecular diagnostics (Pires et al., 2020, MacAulay et al., 2022). These diagnostic platforms align with the concept of precision aquaculture, where early warning systems can significantly reduce economic losses. 4. NANOTECHNOLOGY IN AQUAFEEDS AND NUTRITION Feed accounts for the majority of total production costs in aquaculture, making nutrition a critical determinant of profitability and sustainability. (Can et al, 2023). At the same time, challenges such as nutrient leaching, poor digestibility, and inefficient feed conversion ratios (FCR) reduce overall productivity. Conventional feed additives often degrade rapidly in water or during digestion, limiting their bioavailability to fish (Austin et al., 2022). Nanotechnology provides innovative solutions to improve nutrient stability, bioavailability, and targeted delivery in aquafeeds. Nanoparticles can encapsulate essential nutrients, protect them from degradation, and ensure controlled release, thereby enhancing fish growth, immunity, and overall performance. This section explores the applications of nanotechnology in aquafeeds, focusing on nutrient delivery, functional additives, and fish growth promotion. 4.1. Nano-encapsulation of Nutrients One of the main limitations of conventional aquafeeds is the loss of nutrients into the water before ingestion. Nano-encapsulation addresses this issue by enclosing nutrients within nano-sized carriers, improving their stability and absorption (Nasr-Eldahan et al., 2021). NANOTECHNOLOGY IN AQUACULTURE: INNOVATIONS, APPLICATOINS . . .   57 Proteins and Amino Acids: Encapsulation of essential amino acids such as lysine and methionine improves their bioavailability and reduces leaching losses (Mahotra et al., 2022). Lipids and Fatty Acids: Omega-3 fatty acids, particularly EPA and DHA, are prone to oxidation. Encapsulation in chitosan or lipid nanoparticles prevents oxidative degradation and ensures sustained release (Acosta, 2009). Vitamins and Minerals: Vitamins such as C and E, which are sensitive to heat and light, are stabilized through nano-carriers. Similarly, mineral nanoparticles (e.g., nano-selenium, nano-zinc) enhance absorption efficiency compared to traditional inorganic sources. 4.2. Nano-minerals in Fish Nutrition Minerals are essential micronutrients for bone formation, metabolism, and immunity (Handy, 2012). However, traditional mineral supplements often show low bioavailability. Nano-minerals, due to their high surface area and reactivity, offer enhanced absorption and biological activity. Nano-selenium (SeNPs): Acts as a powerful antioxidant, improving immunity and stress resistance in fish (Rathore et al., 2021; Eissa et al., 2024). Figure 1. Biogenic nanoparticles in sustainable aquaculture. Figure 1. Schematic representation of biogenic nanoparticles in sustainable aquaculture 58   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Nano-zinc (ZnNPs): Plays a vital role in enzyme activation and growth promotion; dietary supplementation improved intestinal morphology in carp (Mondal et al., 2020, Asad et al., 2024). Nano-iron (FeNPs): Enhances hemoglobin synthesis and oxygen transport in fish, reducing anemia-related growth problems (He et al., 2022, Mohammady et al., 2024). However, excessive supplementation of nano-minerals may lead to oxidative stress and accumulation in tissues, emphasizing the need for careful dosage optimization. 4.3. Role of Nanotechnology in Feed Efficiency and Waste Reduction Poor feed conversion leads to nutrient waste, water pollution, and increased production costs. Nanotechnology-based feed formulations improve nutrient assimilation and reduce waste discharge (Almeida et al., 2024). Improved FCR (Feed Conversion Ratio): Fish fed nano-encapsulated nutrients show higher growth rates per unit of feed consumed (Hussain et al., 2019, Eissa et al., 2025). Reduced Nutrient Leaching: Nano-coating of feed particles minimizes nutrient loss to water before ingestion. Environmental Benefits: Lower nutrient excretion reduces eutrophication risks and improves sustainability of aquaculture systems (Almeida et al., 2024). 4.4. Advantages and Limitations 4.4.1. Nano-antimicrobail uses Reduced dependence on antibiotics, stronger and longer-lasting immune responses, more efficient drug delivery with lower dosages, early detection and rapid diagnostics. High production costs of certain nanomaterials, potential toxicity and bioaccumulation in fish and the environment, lack of standardized regulations for nanotechnology applications in aquaculture. Nanotechnology has shown great promise in fish health management by enabling more effective vaccines, innovative drug delivery systems, potent antimicrobial agents, and sensitive diagnostics. These approaches not only reduce reliance on antibiotics but also improve disease prevention and overall fish welfare. However, balancing technological innovation with biosafety and regulatory frameworks remains essential to ensure the responsible adoption of nanotechnology in aquaculture. NANOTECHNOLOGY IN AQUACULTURE: INNOVATIONS, APPLICATOINS . . .   59 4.4.2. Safety and Regulatory Considerations While nanotechnology offers significant nutritional benefits, safety concerns remain. Potential risks include nanoparticle accumulation in fish tissues, oxidative stress, and transfer through the food chain to humans (Can et al., 2011, Handy et al., 2012, Can et al., 2023). Toxicity Risks: High concentrations of nanoparticles may damage gill, liver, or kidney tissues in fish. Regulatory Gaps: Few international guidelines exist regarding the safe inclusion of nanomaterials in aquafeeds (FAO, 2020). Future Direction: Development of eco-friendly and biodegradable nanocarriers (e.g., chitosan, alginate) is recommended to reduce risks. Nanotechnology in aquafeeds represents a transformative approach for improving nutrient delivery, growth performance, and feed efficiency in aquaculture. Nano-encapsulation of nutrients, supplementation with nanominerals, and the use of functional nano-additives contribute to better fish health and sustainability. However, further research is needed to optimize dosages, evaluate long-term safety, and establish clear regulatory frameworks for responsible implementation in commercial aquaculture. 5. POTENTIAL APPLICATION OF ARTIFICIAL INTELLIGENCE IN NANOTECHNOLOGY-DRIVEN AQUACULTURE The rapid advancement of nanotechnology and artificial intelligence (AI) is transforming modern aquaculture toward greater efficiency, sustainability, and precision. Both technologies complement each other, providing new tools for disease prevention, feed optimization, and environmental monitoring. Nanotechnology offers innovative solutions through the development of nanoscale materials such as metallic nanoparticles (Ag, ZnO, TiO₂), polymeric nanoparticles (chitosan, PLGA), and lipid-based nanocarriers. These materials are applied as antimicrobial agents, vaccine carriers, biosensors, and nutrient delivery systems, improving fish health and growth performance (Austin et al., 2022). Nanobiosensors, in particular, allow real-time detection of pathogens and toxicants in water, enabling rapid and targeted responses (Can et al., 2023). Artificial intelligence complements these advances by managing the vast datasets generated by sensors, imaging devices, and farm monitoring systems. Machine learning and deep learning models analyze fish behavior, detect disease symptoms, and predict stress events based on water quality or environmental 60   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I fluctuations (Shreesha et al., 2023, Roja et al., 2025). Integrating AI with Internet of Things (IoT) devices and cloud computing supports continuous monitoring and data-driven decision-making across aquaculture operations. The convergence of nanotechnology and AI is an emerging frontier in aquaculture. For instance, AI-driven data analytics can interpret signals from nanosensors to enhance early disease diagnostics and optimize treatment strategies. Similarly, predictive AI models can guide the safe and efficient application of nanomaterials, minimizing ecological risks. Future developments are expected to focus on AI-assisted nanobiosensing systems and smart aquaculture platforms, driving sustainable and resilient aquatic food production. 6. NANOTECHNOLOGY IN WATER TREATMENT 6.1. Removal of Organic Pollutants Nanomaterials such as titanium dioxide (TiO₂), zinc oxide (ZnO), and graphene-based composites act as photocatalysts under UV or visible light, breaking down organic matter including antibiotics, pesticides, and excess feed residues (Nezhadheydari et al., 2019, Ogunfowora et al., 2021). TiO₂ nanoparticles effectively degraded oxytetracycline residues in aquaculture wastewater, reducing antibiotic resistance risks (Do et al., 2019; Chin et al., 2025). 6.2. Heavy Metal Removal Aquaculture effluents may contain heavy metals (e.g., copper, cadmium, lead) from feed additives or nearby industries. Nano-adsorbents, such as iron oxide nanoparticles and functionalized carbon nanotubes, exhibit high binding capacity for these pollutants (Ogunfowora et al., 2021; El-Naggar et al., 2022a). 6.3. Nutrient Control Excess nitrogen and phosphorus from uneaten feed contribute to eutrophication. Nanostructured zeolites and biochar composites have been tested for their ability to capture ammonium and phosphate ions (Wang et al., 2021; Deng et al., 2022). 6.4 Nanotechnology in Waste Management Environmental sustainability is one of the greatest challenges facing aquaculture. Intensification of fish farming leads to nutrient-rich effluents, pathogen proliferation, and chemical contamination, which in turn affect aquatic NANOTECHNOLOGY IN AQUACULTURE: INNOVATIONS, APPLICATOINS . . .   61 ecosystems and public health (Austin et al., 2022). Conventional water treatment methods—such as mechanical filtration, biofilters, and chemical disinfection— are often insufficient or costly for large-scale applications. Nanotechnology provides innovative tools for water purification, pollutant removal, and ecosystem monitoring. Nanomaterials, due to their large surface area, high reactivity, and catalytic properties, have been investigated for wastewater treatment, pathogen inactivation, and reduction of environmental footprints in aquaculture systems (Can et al., 2011, Austin et al 2022). Nanotechnology can also improve solid waste management in aquaculture: Nano-enzymes (nanozymes): Mimic natural enzymatic activity and accelerate the breakdown Nanostructured membranes: Enhance the efficiency of recirculating aquaculture systems (RAS) by filtering microplastics, pathogens, and suspended solids (Maodiswari et al., 2024). 6.5. Antimicrobial Nanomaterials for Water Disinfection Pathogen control is essential for maintaining water quality and fish health. Metallic nanoparticles, especially silver (Ag) and copper (Cu) nanoparticles, have potent antimicrobial properties. Mechanism of Action: Nanoparticles disrupt microbial membranes, generate reactive oxygen species, and interfere with DNA replication (Rai et al., 2012). Application: Incorporation of silver nanoparticles into aquaculture filters reduced Vibrio spp. and Aeromonas hydrophila counts significantly (Thanigaivel et al, 2021; Rajeshkumar & Bharath, 2017). However, excessive nanoparticle use may lead to bioaccumulation in aquatic organisms, highlighting the importance of controlled applications. 6.6. Biosensing and Environmental Monitoring Early detection of pollutants and pathogens is critical for sustainable aquaculture. Nanotechnology-based biosensors offer sensitive, rapid, and lowcost monitoring tools. Carbon nanotube (CNT)-based sensors: Detect ammonia and nitrite at trace levels in aquaculture water (Cho et al., 2022; Balram et al., 2025). Quantum dot sensors: Used for monitoring heavy metal contamination and toxins in aquatic environments (Chen et al., 2015; Gupta et al., 2024; Batool et al., 2025). 62   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I These biosensing systems enable real-time monitoring, supporting decision-making in water management. 6.7. Benefits and Limitations Benefits: High efficiency in pollutant removal compared to conventional methods, reduction in antibiotic and chemical disinfectant use, real-time monitoring through nanosensors, support for closed-loop, eco-friendly aquaculture systems. Limitations: Potential ecotoxicity of nanoparticles if not properly managed., high production and application costs, lack of standardized protocols for nanoparticle use in aquaculture wastewater treatment (Handy et al., 2012). 7. FUTURE PROSPECTS AND CHALLENGES IN NANOTECHNOLOGY FOR AQYACULTURE Nanotechnology has shown great potential in aquaculture, offering applications in fish health management such as Eco-friendly nanomaterials, nutrition and environmental sustainability and Circular economy approaches (Can et al, 2011; Saliu et al., 2021), and Integration with IoT and AI. However, its long-term adoption will depend on how effectively the industry addresses challenges related to safety, cost, regulatory approval, and social acceptance. This section explores the future directions of nanotechnology in aquaculture and the barriers that must be overcome to ensure safe and sustainable applications. 7.1. Future Prospects 7.1.1. Precision Aquaculture through Nanotechnology The future of aquaculture will likely integrate nanotechnology with digital technologies such as artificial intelligence (AI), big data, and the Internet of Things (IoT). Nano-biosensors embedded in aquaculture systems could continuously monitor water quality, pathogen loads, and fish metabolism in real time, enabling precision aquaculture management. 7.1.2. Next-Generation Vaccines and Drug Delivery Nanoparticle-based vaccines are expected to play a major role in controlling fish diseases, particularly as antibiotic use faces increasing restrictions (Thompson et al., 2023). Future vaccine formulations may combine multi-antigen delivery, mucosal targeting, and controlled release, improving protection levels against bacterial, viral, and parasitic infections. Similarly, NANOTECHNOLOGY IN AQUACULTURE: INNOVATIONS, APPLICATOINS . . .   63 nanocarriers may enhance the targeted delivery of antiparasitic and antifungal drugs, reducing dosage requirements and side effects. 7.1.3. Sustainable Feeds and Circular Economy Nanotechnology can contribute to the development of eco-friendly aquafeeds, including encapsulation of alternative proteins (e.g., insect meal, algae) and the recovery of nutrients from waste streams. For example, nanobiochar composites could recycle phosphorus from aquaculture effluents back into feed formulations, supporting a circular economy. 7.1.4. Eco-Friendly Nanomaterials The future will see a shift from inorganic nanoparticles (e.g., silver, zinc oxide) toward biodegradable and biocompatible nanomaterials such as chitosan, alginate, and plant-derived nanocarriers. These materials reduce ecotoxicological risks while maintaining efficiency in nutrient delivery and water treatment. 7.1.5. Global Standards and Certification International certification programs such as GlobalG.A.P. and Aquaculture Stewardship Council (ASC) may include nanotechnology-related criteria in the future, ensuring traceability, safety, and consumer confidence (FAO, 2020). 7.2. Challenges Despite promising applications, nanotechnology in aquaculture faces significant barriers: 7.2.1. Safety and Ecotoxicity The potential for bioaccumulation of nanoparticles in fish tissues and their transfer along the food chain to humans remains a critical concern (Handy et al., 2012). Studies have shown that silver and carbon-based nanoparticles can induce oxidative stress and DNA damage in aquatic species (Freixa et al., 2018; Krishnasamy et al., 2023; Gamoń et al 2023). Long-term ecological effects are still poorly understood, requiring comprehensive risk assessments. 7.2.2. Economic Constraints High production costs of nanoparticles limit their adoption in small and medium-scale aquaculture operations. While nano-encapsulation improves 64   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I efficiency, the cost-benefit ratio must be carefully evaluated to ensure affordability for farmers. 7.2.3. Regulatory and Legal Frameworks Currently, few countries have clear regulations governing the use of nanomaterials in aquaculture feeds, vaccines, or water treatment. The absence of standardized testing protocols creates uncertainty for manufacturers and limits large-scale commercialization (FAO, 2020). 7.2.4. Public Perception and Consumer Acceptance Consumers often associate the word “nano” with risk and artificial manipulation, which may affect market acceptance of nano-based aquaculture products. Transparent communication, labeling, and safety certification will be crucial for public trust.. 7.2.5. Technical and Knowledge Gaps The successful application of nanotechnology requires expertise in materials science, fish physiology, and aquaculture engineering. A lack of interdisciplinary collaboration and limited access to training may slow down adoption, particularly in developing countries. 8. CONCLUSION Nanotechnology represents a transformative approach for advancing sustainable aquaculture. Over the past decade, a growing body of research has demonstrated the potential of nanoparticles to improve fish health, nutrition, and environmental management, addressing key challenges that traditional aquaculture practices cannot fully resolve. Addressing these challenges will require interdisciplinary collaboration, rigorous research on long-term impacts, cost-effective production methods, and transparent communication with stakeholders. The future of aquaculture will likely see the widespread adoption of eco-friendly, biodegradable nanomaterials, combined with AI-driven monitoring and precision management systems. Key research directions include: Development of sustainable nano-carriers for nutrients, drugs, and vaccines. 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(2023). Inorganic nanoparticles for use in aquaculture. Reviews in Aquaculture, 15(4), 1600-1617. https://doi.org/10.1111/raq.12803 Wang, Y., Song, X., Xu, Z., Cao, X., Song, J., Huang, W., ... & Wang, H. (2021). Adsorption of nitrate and ammonium from water simultaneously using composite adsorbents constructed with functionalized biochar and modified zeolite. Water, Air, & Soil Pollution, 232(5), 198. https://doi.org/10.1007/ s11270-021-05145-9 77 CHAPTER III MARINE MALACOSTRACA IN TÜRKİYE: A COMPREHENSIVE REVIEW ON BIODIVERSITY AND WASTE UPCYCLING Özge Özgen Dokuz Eylül University, Institute of Marine Sciences and Technology, Department of Marine Living Resources, Izmir, Türkiye Email: [email protected], ORCID: https://orcid.org/0000-0001-8228-4817 1. Introduction Marine ecosystems are among the most complex and dynamic systems on Earth, where biodiversity, ecological interactions, and human activities are closely interconnected. Crustaceans, which are a diverse and ecologically significant group within the phylum Arthropoda, consist of over 52,000 described species that inhabit marine, freshwater, and terrestrial ecosystems (Ghafor, 2020). They play crucial roles in aquatic food webs, contributing to nutrient cycling, energy flow, and the structuring of communities (Szaniawska, 2018). The class Malacostraca is the largest group of crustaceans, with approximately 30,000 marine, freshwater, and terrestrial species worldwide. This class includes amphipods, decapods, isopods, mysids, and cumaceans, among others. Malacostracans are notable for their exceptional diversity, ecological adaptability, and functional importance. They inhabit almost every possible marine niche, from intertidal zones to the deepest parts of the ocean (Martin & Davis, 2001; Rogers et al., 2020; Szaniawska, 2018). Four seas surround Türkiye: the Black Sea, the Sea of Marmara, the Aegean Sea, and the Levantine Sea. Together, these waters form a unique biodiversity hotspot characterized by distinct hydrographic features, intricate circulation systems, and significant human pressures. They not only support 78   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I diverse populations of native malacostracans but also serve as vital entry points for alien and invasive species, primarily through the Suez Canal (Çınar et al., 2021; Galil et al., 2015). Rapidly increasing drivers such as habitat degradation, climate change, and biological invasions have intensified concerns about the resilience and sustainability of native biodiversity in the region. Global discussions surrounding the blue economy and circular bioeconomy have increasingly focused on the sustainable use of marine resources, particularly the valorization of crustacean by-products (UNEP/MAP, 2016). The seafood processing industry generates substantial quantities of crustacean waste, which has traditionally been regarded as low-value biomass. However, this waste now presents new opportunities through blue biorefineries. By transforming shells and exoskeletal residues into high-value products such as biopolymers, proteins, and bioactive compounds, these innovative approaches not only reduce environmental impacts but also contribute to achieving sustainable development goals (Aneesh et al., 2023; Kiehbadroudinezhad et al., 2023; Rossi et al., 2024). This review chapter synthesizes current knowledge on the biodiversity, ecosystem functions, and biotechnological applications of Malacostraca in Türkiye. Specifically, it aims to: (1) provide an updated overview of species richness and ecosystem services across the Turkish seas; (2) highlight alien and invasive species, along with their ecological implications; (3) assess the role of malacostracans as ecological indicators in the context of European Union directives, such as the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD); and (4) introduce the current status of waste evaluation through blue biorefinery concepts. By integrating ecological, conservation, and biotechnological perspectives, this chapter presents a comprehensive framework for advancing the sustainable management of marine Malacostraca. 2. Biodiversity And Ecosystem Services Of Malacostraca In Türkiye The marine malacostracan fauna of Türkiye displays significant species richness and biogeographic diversity across different sea basins. Of the approximately 3,000 marine malacostracan species identified in the Mediterranean Sea (WoRMS, n.d.), 903 have been reported in Turkish waters. This underscores Türkiye’s significance as a biodiversity hotspot in the region (Aslan, 2024; Báez et al., 2025; Bakır et al., 2024; Christidis et al., 2024; Çınar et al., 2024; Özgen & Açık, 2024). MARINE MALACOSTRACA IN TÜRKİYE: A COMPREHENSIVE REVIEW ON . . .   79 The highest diversity of species in Turkish seas is found in the Aegean Sea, which hosts 706 species, followed by the Levantine Sea with 577 species, the Sea of Marmara with 490 species, and the Black Sea with 206 species (Figure 1). This distribution pattern is influenced by various environmental factors, including salinity gradients, substrate diversity, circulation systems, primary productivity, and anthropogenic pressures (Bakır et al., 2024). Among the different orders of malacostracans, Amphipoda and Decapoda are the most diverse. Amphipods are most abundant in the Aegean Sea (313 species) and the Levantine Sea (230 species), thriving in complex coastal habitats such as rocky reefs, seagrass meadows, and mussel farms. Similarly, decapods reach their peak diversity in the Aegean (233 species) and Levantine (229 species) seas (Figure 1) (Aslan, 2024; Báez et al., 2025; Bakır et al., 2024; Christidis et al., 2024; Çınar et al., 2024; Özgen & Açık, 2024). Figure 1. The number of marine Malacostraca species along the Turkish coasts (NEB: Nebaliacea; STO: Stomatopoda; LOP: Lophogastridae; MYS: Mysida; AMP: Amphipoda; ISO: Isopoda; Tan: Tanaidacea; CUM: Cumacea; EUP: Euphausiacea; DEC: Decapoda) 80   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Other malacostracan orders, while not as species-rich, play vital roles in ecosystem functioning. Mysids (Mysida), lophogastrids (Lophogastrida), and euphausiids (Euphausiacea) are essential components of planktonic food webs, serving as prey for fish and gelatinous zooplankton (Castellani & Edwards, 2017; Rogers et al., 2020). Cumaceans, tanaidaceans, and isopods contribute to sediment turnover and the processing of detritus, thereby enhancing the coupling between benthic and pelagic environments (Rogers et al., 2020; Szaniawska, 2018). Specialized taxa exhibit additional ecological functions: for instance, Chelura terebrans (Amphipoda) and Limnoria spp. (Isopoda) act as natural recyclers of submerged wood (Sivrikaya, 2019). Commensal organisms such as Podocerus chelonophilus (associated with sea turtles) and Isaea montagui (found on Maja crabs) highlight important epibiotic and symbiotic relationships (Sezgin et al., 2009; Vader & Tandberg, 2015). Additionally, parasitic amphipods like Acidostoma laticorne and Brachyscelus rapacoides illustrate the ecological diversity within this group (Bakır et al., 2024; Christidis et al., 2024). 2.1. Alien And Invasive Malacostracan Species In Türkiye The geographic position of the Mediterranean Sea, which connects the Indo-Pacific and the Atlantic through the Suez Canal and the Strait of Gibraltar, makes its marine ecosystems particularly vulnerable to biological invasions. Human activities such as maritime traffic, ballast water discharge, aquaculture practices, and climate-driven migrations have significantly accelerated the introduction and establishment of alien species along its coasts (Çınar et al., 2021; Katsanevakis et al., 2014). By the end of 2020, a total of 539 alien marine species had been documented in Turkish waters. Of these, 79 belong to the phylum Arthropoda, and 57 are classified within Malacostraca. This includes 45 decapods, four amphipods, three isopods, three stomatopods, one cumacean, and one tanaidacean. Notably, 45 of these species are identified as Lessepsian migrants, having entered the Mediterranean through the Suez Canal. Among these, 11 species are classified as invasive decapods, exhibiting rapid population growth, ecological competitiveness, and significant impacts on native biodiversity and ecosystem services (Çınar et al., 2021) (Figure 2). MARINE MALACOSTRACA IN TÜRKİYE: A COMPREHENSIVE REVIEW ON . . .   87 3.1.3. Polysaccharides Chitin and chitosan are the primary polysaccharides in malacostracan shells, valued for biodegradability, biocompatibility, antimicrobial properties, and versatility (Shahidi & Abuzaytoun, 2005). 3.1.3.1. Chitin Chitin is the second most abundant natural biopolymer after cellulose (Berezina, 2016). It serves as the structural matrix of crustacean exoskeletons and is also found in the cell walls of fungi, the perisarc of hydrozoans, and the epidermal cuticle of many invertebrates (Hamed et al., 2016). Traditionally, chitin is extracted through a chemical process that involves demineralization using hydrochloric acid or acetic acid, followed by deproteinization with sodium hydroxide (Kim & Park, 2015). In recent years, biological extraction methods have emerged as more sustainable alternatives to traditional methods. These newer methods include demineralization using organic acid-producing bacteria, such as Lactobacillus plantarum ATCC 14917 and Bacillus subtilis ATCC 6051, and deproteinization using protease-producing bacteria, including Streptomyces sp. SCUT-3 and Paenibacillus mucilaginosus TKU032. These approaches reduce hazardous waste and align with eco-friendly extraction practices (Lu et al., 2023; Rossi et al., 2024). 3.1.3.2. Chitosan Chitosan is a linear polysaccharide derived from the deacetylation of chitin, typically using concentrated sodium hydroxide at elevated temperatures. It is the only known natural cationic polysaccharide(Du et al., 2014). In comparison to chitin, chitosan is more versatile due to its water solubility and enhanced biological activities, which include antimicrobial, antioxidant, and film-forming properties. These characteristics make chitosan suitable for a wide range of applications, including agriculture (as biofertilizers and seed coatings), medicine (in drug delivery systems and surgical sutures), food packaging (as antimicrobial and biodegradable films), and environmental engineering (as adsorbents for heavy metals and dyes) (Rossi et al., 2024). 3.1.4. Lipidic Compounds Though present in smaller amounts, lipidic fractions—particularly carotenoids and fatty acids—are nutritionally and commercially significant (Rossi et al., 2024; Zhang et al., 2024). 88   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I 3.1.4.1. Carotenoids Carotenoids, such as astaxanthin and β-carotene, abundant in shrimp and crab shells, provide pigmentation and act as potent antioxidants. Extraction typically uses organic solvents or supercritical CO₂. Applications extend from aquaculture feeds to cosmetics and functional foods (López et al., 2021; Rossi et al., 2024). 3.1.4.2. Fatty Acids Seafood products are rich in essential fatty acids like omega-3 and omega6, as well as vitamins and minerals not commonly found in many land-based protein sources (Azelee et al., 2023). Malacostracan by-products are rich sources of various fatty acids, including saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and especially polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are widely recognized for their cardiovascular, anti-inflammatory, and neuroprotective benefits (Kotlyarov & Kotlyarova, 2022). Extraction relies on solvent or supercritical CO₂ methods, and the PUFA-rich fractions are valuable in nutraceuticals and dietary supplements (Gómez-Estaca et al., 2017; Liu et al., 2021). 4. Conclusion And Perspectives Malacostracan crustaceans are among the most diverse and ecologically significant components of Türkiye’s marine ecosystems. Their distribution across the Black Sea, Marmara, Aegean, and Levantine Seas reflects the region’s rich natural biodiversity, as well as the pressures from human activities, including pollution, overfishing, habitat modification, and biological invasions. Malacostracans provide crucial ecosystem services, including detritus processing, benthic–pelagic coupling, habitat engineering, and trophic regulation. Additionally, they play a central role in socio-economic systems through fisheries and aquaculture. However, significant challenges are emerging. Alien and invasive malacostracan species are altering community structures, outcompeting native species, and contributing to biotic homogenization, particularly along the Aegean and Levantine coasts (Çınar et al., 2021; Katsanevakis et al., 2014). Several native decapods, which have high commercial and ecological value, remain under threat. Effective conservation frameworks are needed that integrate national policies with international agreements, such as the Bern Convention and the Barcelona Convention. MARINE MALACOSTRACA IN TÜRKİYE: A COMPREHENSIVE REVIEW ON . . .   89 Malacostracans also serve as highly effective indicator taxa in ecological quality assessments mandated by EU frameworks, such as the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD). Amphipods, isopods, and other benthic groups are especially valuable bioindicators, providing sensitive metrics of organic enrichment, pollution, and overall ecosystem integrity (Borja et al., 2000; Çınar et al., 2012). Strengthening their role in bioassessment programs will enhance ecological monitoring and foster ecosystem-based management approaches. Equally important is the revaluation of malacostracan by-products as raw materials within a blue biorefinery context. Crustacean shells and processing residues can be transformed into high-value compounds—including chitin, chitosan, proteins, carotenoids, and PUFAs—thereby reducing organic pollution while supporting innovation in biotechnology, pharmaceuticals, food industries, and environmental engineering (Rossi et al., 2024; Vidal et al., 2022). Such valorization directly contributes to multiple United Nations Sustainable Development Goals (SDGs), bridging ecological sustainability with economic opportunity. Looking forward, a comprehensive strategy for the sustainable management of marine Malacostraca in Türkiye should prioritize: · Comprehensive monitoring programs to track biodiversity patterns, invasive species, and ecological health indicators. · Conservation and restoration measures for threatened and legally protected decapods, coupled with effective enforcement mechanisms. · Adaptive management frameworks that account for climate-induced range shifts and the dynamics of invasive species. · Investment in blue biorefineries, fostering circular economy practices that integrate environmental protection with industrial growth. · Regional and international cooperation, aligning national actions with broader Mediterranean and EU biodiversity strategies. By integrating taxonomic, ecological, conservation, and biotechnological perspectives, this synthesis highlights the pivotal role of Malacostraca in sustaining marine ecosystem resilience. 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Therefore, the future of cell-cultured seafood will depend not only on technical feasibility but also on the establishment of robust food safety standards and effective public communication strategies. For cellular aquaculture to fully supplant traditional methods, challenges related to scalability, cost, and regulation must be addressed. While it may not completely eliminate all disease risks, it can significantly reshape the risk landscape in favor of greater safety and sustainability. Future research should focus on optimizing production efficiency and conducting long-term safety studies. This is a critical step toward a future where seafood production can meet global demand without compromising health, ecosystems, or food safety. References Ahmed, A. S., Billah, M. M., Ali, M. M., Bhuiyan, M. K. A., Guo, L., Mohinuzzaman, M.,Cai, W. (2023). Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies. 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Prof. Dr.) Ege University, Department of Aquaculture, Faculty of Fisheries, Izmir, Türkiye E-mail: [email protected], ORCID: 0000-0002-5609-5630 2(Assoc. Prof. Dr.) Izmir Katip Celebi University, Department of Aquaculture, Faculty of Fisheries, Izmir, Türkiye E-mail: [email protected], ORCID: 0000-0002-2179-1900 1. Introduction Aquaculture has been documented in China since before 1000 BCE. Carp, a lucky charm, was initially described as being raised to meet nutritional needs by the Zhou dynasty (1112-221 BCE) and later by the political leader Fan Li approximately 500 BCE (Wang et al., 2020). Farmers created the first type of polyculture after focusing on related fish in the Cyprinidae family. Ponds were also made more nutrient-dense and enriched of algae by adding wastes from animal husbandry. China developed the first combined agriculture-aquaculture systems, which are still in use there today (Martínez‐Porchas et al., 2010). The history of inland aquaculture in Europe dates back to the middle ages, when fishponds were used to supplement local fish supplies, especially on monastery and estate lands. Carp (Cyprinus carpio) was again important species in European aquaculture history as well (Hoffman 2005). Nowadays, fish breeding in inland aquaculture is the controlled process of reproducing fish under managed conditions to ensure a reliable supply of fry and fingerlings for grow-out stages. Unlike fisheries, aquaculture breeding enables 106   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I successful spawning every year, selective improvement of desirable traits in order to lower production costs and increase productivity, and sustainable management of natural resources. Inland aquaculture covers a wide range of systems, from basic earthen ponds to high-tech floating cages in rivers and lakes. In extensive pond culture, fish feed on naturally occurring aquatic nutrients. Semi-intensive systems supplement this with added feed, while intensive systems require mechanical aeration to maintain oxygen levels. Super-intensive systems often operate indoors, using heated tanks and advanced water treatment technologies like Recirculating Aquaculture Systems (RAS). These systems can also be integrated with agriculture in closed-loop, “circular” setups that recycle water and nutrients, such as integrated agri-aquaculture and aquaponics. Thus, when planning a breeding program, culture systems and protocols are very crucial environmental effects to be considered carefully for the success of the program. The breeding process, which mean to be intensively controlled, requires a multidisciplinary approach, integrating fish biology, water quality, feeding, genetics, and engineering. Effective management of each stage from broodstock regulations to larval rearing determines the overall success of an aquaculture company. 2.Principles of Breeding in Aquaculture Breeding as a term is more than a culture process, referring a progressive production controlling environment and fully or partially considering genetic parameters at the same time. Breeding special lines and inter or intra species hybridization are pivotal genetic strategies in aquaculture. These strategies allow breeders to improve characteristics such as growth rate, resistance to disease, and environmental tolerance in species like tilapia and Asian seabass. Breeding special lines involves selecting breeders who to mate within a genetically distant line to fix desirable traits, but can lead to reduced genetic variation and increased inbreeding over generations, potentially causing inbreeding depression and loss of adaptability (Varney and Wilbur, 2020; D’Ambrosio et al., 2019; Janssen et al. 2017). Hybridization (crossbreeding between different lines or species) may cause heterosis (hybrid vigor), resulting in offspring with superior growth, survival, and sometimes improved nutritional quality compared to pure lines. This approach can also restore genetic variation and prevent inbreeding depression (Jiang et al., 2025; Goyard et al., 2008; Xiao 2006; Wang et al., 2018) FISH BREEDING IN INLAND AQUACULTURE   107 Key principles in applications include: · Mimicking environmental conditions; such as temperature changes, or photoperiod that normally trigger spawning. · Optimizing survival rates by minimizing cannibalism in the ponds or tanks, and disease risks existing in natural environments. · Genetic improvement through selective breeding increases traits such as growth rates, disease resistance, feed conversion rates and fegundity. · Scalability to meet the needs of small-scale farmers as well as large industrial hatcheries. 3. Broodstock Management Effective broodstock management is essential for the sustainable development of inland aquaculture. This process directly influences egg quality, genetic variation and overall productivity (Nima et al., 2024). Table 1. presents conditioning parameters information for some species subjected inland aquaculture process worldwide. Table 1. Optimal Broodstock Ratios and Conditioning Parameters* Species Male:Female Ratio Maturity Age Conditioning Feed Key Notes Tilapia 1:2–3 6–12 months 25–30% protein diet Breed naturally in ponds Common carp 1:1 2–3 years 30–35% protein + vitamins Require induced spawning Catfish 1:2 1–2 years 35% protein diet + live feed supplement Hormonal induction common Trout 1:1 2–3 years High-protein,highfat cold-water diet Spawning triggered by photoperiod *Data compiled from Huet (1986), Bromage & Roberts (1995), Pillay & Kutty (2005), Stickney (2005), and Woynarovich et al. (2011). 3.1. Selection The success of any breeding program depends on the quality of broodstock population in the very beginning. Thus, while forming the base population for a breeding program there are key points to take care either phenotypical or genotypic aspects. The chosen fish must be healthy and free from disease 108   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I and deformities. The selective breeding process should consider traits like fast growth, high fecundity and good flesh quality. It is also very important to avoid inbreeding by obtaining breeders from multiple populations. 3.2. Conditioning Broodstock must undergo a preparation period before spawning: · Diet: Protein-rich feed (25–35%) supplemented with vitamins, minerals, and essential fatty acids. · Environment: Low-stress tanks or ponds with stable water parameters. · Duration: Conditioning usually lasts several weeks, ensuring gonadal maturation, depending on the species. 3.3. Sex Ratios Maintaining appropriate male-to-female ratios improves fertilization rates, again depending on the species as given in Table 1. 4. Spawning Techniques Obtaining fertilized eggs has been carried out in three ways: natural spawning, hormonal induction or stripping. Spawning technique is very important while building a breeding program in different aspects. The most important subject for the success and sustainability of a breeding program is genetic variation within the selected strains. Genetic variation amount of the further generations mostly depends on the first generation. 4.1. Natural Spawning Some species, such as tilapia, spawn readily in ponds if substrates or nesting sites are provided. This method is simple but harder to control in terms of timing and egg collection. Another disadvantage of this method is the difficulty in determining the breeders to be used in production. 4.2. Hormonal Induction Species like Indian major carps and catfishes often require hormonal induction. For this process: · Pituitary extracts (from carp or catfish) are traditional stimulants. FISH BREEDING IN INLAND AQUACULTURE   109 · Synthetic hormones like GnRH analogues (e.g., Ovaprim and Ovatide) are widely used. · Injections stimulate ovulation and spermatogenesis, after which stripping is performed. 4.3. Artificial Fertilization Stripping involves gently pressing eggs and sperm from breeders into a container, where they are mixed with water to activate sperm. This ensures higher fertilization rates compared to uncontrolled spawning and makes possible to separate good quality fertilized eggs. Another advantage of this method is easy determination of the breeders to be used for the production and selection processes. 5. Egg Incubation Incubating eggs are the second sensitive process for the success of the program. Each species has its own requirements depending on the natural habitat conditions. Incubation parameters are essential for the fish development and should be kept within optimum values during aquaculture production. Table 2. presents incubation conditions for the common inland aquaculture species. Table 2. Incubation Conditions for Common Aquaculture Species* Species Temp. Range (°C) DO Requirement Hatching Time Incubation Method Tilapia 26–30 >6 mg/L 1–2 days Mouthbrooding/ hapas Common carp 24–28 >6 mg/L 3–4 days McDonald jars Catfish 25–28 >5 mg/L 2–3 days Vertical jars Trout 12–15 >7 mg/L 20–30 days Trays / raceways *Huet (1986), Bromage & Roberts (1995), Pillay & Kutty (2005), Stickney (2005), Boyd (2015), Zohar et al. (2001) and Woynarovich et al. (2011). 5.1. Incubation Systems Different incubation systems are used in inland aquaculture according to the species and physical conditions and three of them are very common (Figure 1). 110   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Figure 1. Egg Incubation Systems (Huet 1986, Woynarovich et al. 2011, Bromage & Roberts 1995). 5.2. Duration Hatching time varies depending on the species: · Tilapia: 1–2 days · Common carp: 3–4 days · Trout: 20–30 days (trout needs cold water and cold water slows development) 6. Larval Rearing First feeding strategies from live food to the feed mixtures according to species are presented in the Table 3. Newly hatched larvae depend on their yolk sac. Once absorbed yolk sac, live feed such as rotifers, Artemia nauplii, or cladocerans must be given in order to complete larval developmental stages. Introduction of micro-pellets gradually reduces reliance on live feed. Nutritionally optimized starter feeds improve growth and survival. High stocking densities increase stress and cannibalism. Optimal density depends on species, and it should allow fish to swim and feed freely. Table 3. First Feeding Strategies* Species YolkSac Duration First Feed Transition Feed Notes Tilapia 2–3 days Rotifers Powdered feed Fry often mouthbrooded Carp 3–4 days Cladocerans Micro-pellets Stocking density must be moderate Catfish 2–3 days Artemia nauplii Micro-diets High cannibalism risk Trout 10–15 days Artemia + starter crumble Pellet feed Cold-water slow development *Huet (1986), Bromage & Roberts (1995), Pillay & Kutty (2005), Stickney (2005), Boyd (2015), Zohar et al. (2001) and Woynarovich et al. (2011). FISH BREEDING IN INLAND AQUACULTURE   111 7. Nursery Phase In inland aquaculture, the nursery phase is a crucial transitional period that connects the more durable fingerling stage with the vulnerable larval stage. In order to increase survival, consistent growth, and for being ready for stocking into grow-out systems, fry are reared under controlled conditions during this time. Good quality fry grow into strong fingerlings that can resist the strains of transit and subsequent culture requires proper nursery management, which includes pond preparation, water quality, feeding, and grading. Overall production efficiency is increased with close attention to nursery techniques because mortality is usually higher during the early life stages. Figure 2. Nursery Pond Preparation Cycle (flow diagram). Steps in the nursery pond preparation cycle are based on FAO pond management guidelines (FAO, 2001), Boyd (2018) on fertilization practices, and training module materials (AQUACULTURE NC II), which outline best practices in hatchery and nursery operations. 8. Genetic Management in Hatchery Effective genetic management is a cornerstone of modern inland aquaculture. While water quality, nutrition, and disease control determine immediate survival, genetic diversity and improvement programs ensure longterm productivity and resilience. Without proper practices, hatchery-reared stocks often suffer from inbreeding depression, poor growth performance, and reduced adaptability (Hulata, 2001; FAO, 2004). 8.1. Avoiding Inbreeding Depression Sustained selective breeding without genetic refreshment can reduce genetic diversity and increase inbreeding, necessitating periodic crossbreeding to maintain population health (Varney and Wilbur, 2020; Liang et al., 2023). Inbreeding occurs when related individuals are repeatedly bred together, reducing heterozygosity and leading to slower growth, lower fertility, higher susceptibility to diseases, and deformities (Nguyen, 2016). To prevent this, 112   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I hatcheries must maintain large and diverse broodstock populations (an effective population size of at least 50 for short-term stability and 500 or more for longterm sustainability) has been recommended (Gjedrem et al., 2012). Broodstock rotation, seasonal renewal, and occasional introduction of new genetic material from unrelated populations help maintain genetic variation. 8.2. Broodstock Rotation and Renewal Broodstock should be renewed every 2–3 years for fast-growing species such as tilapia and every 4–5 years for slower-maturing species like carp and catfish (FAO, 2004). Incorporating wild brooders or unrelated hatchery stocks helps prevent genetic drift and the buildup of harmful recessive traits. 8.3. Selective Breeding Programs Selective breeding is one of the most effective tools in aquaculture improvement. It targets traits such as faster growth, improved feed conversion efficiency, disease resistance, and higher product quality (Gjedrem et al., 2012). A well-known example is the GIFT strain (Genetically Improved Farmed Tilapia) developed by WorldFish, which shows up to 85% higher growth rates compared to unimproved strains (Eknath & Acosta, 1998). Similar programs have been implemented in carp and catfish, while salmonids benefit from family-based and genomic selection approaches. 8.4. Hybridization and Crossbreeding Hybridization between different strains or species can generate hybrid vigor (heterosis), with offspring outperforming parental lines in growth or disease resistance (Hulata, 2001). For example, hybrid catfish (♀ Channel catfish × ♂ Blue catfish) in the U.S. demonstrate superior growth and stress tolerance. However, hybrids must be carefully managed to avoid ecological risks such as genetic pollution of wild stocks (FAO, 2004). 8.5. Marker-Assisted and Genomic Selection Modern programs increasingly employ DNA markers to accelerate breeding progress. Marker-assisted selection and genomic selection improve accuracy, shorten generation intervals, and increase genetic gain (Nguyen, 2016). For instance, SNP markers are being used in tilapia and salmon to improve resistance against bacterial pathogens and sea lice. 119 CHAPTER VI PROPOLIS AS A NATURAL THERAPEUTIC IN SUSTAINABLE AQUACULTURE: CURRENT AND FUTURE PERSPECTIVES ON FISH HEALTH Deniz ÇİRA1* & Erkan CAN2 (Res. Assist.) Department of Aquaculture and Aquatic Animal Diseases, Faculty of Veterinary Medicine, Istanbul University-Cerrahpaşa, 38000 Istanbul, Türkiye E-mail: [email protected] ORCID: 0000-0002-1831-6017 (Prof.Dr.) Department of Aquaculture, Faculty of Fisheries, Izmir Katip Celebi University, 38000 Izmir, Türkiye E-mail: [email protected] ORCID: 0000-0001-9440-7319 1. Introduction The discovery of antimicrobials, including β-lactams, tetracyclines, and aminoglycosides, revolutionized the treatment of infectious diseases. Nevertheless, the widespread misuse and overuse of these agents have accelerated the emergence of antimicrobial resistance (AMR), which can be transmitted from domestic animals to humans and is recognized by the WHO as a major global threat to both human and animal health (Svetikiene et al., 2024). In recent years, the use of chemicals targeting infectious organisms in the growing fishing and aquaculture industries has had negative effects on animals, humans, and the environment. Therefore, there is a need for alternative products to minimize these risks (Farag et al., 2021). 120   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Phytotherapeutic agents, compounds that have long been used against bacterial and parasitic infections in humans and animals, also show potential in aquaculture. Recent in vitro and in vivo studies have demonstrated that these compounds may be effective in controlling bacterial, parasitic, and fungal pathogens in fish (Valladão, Gallani, Pilarski, 2015). Chemicals used to treat diseases in fish farms present a risk to human health due to their accumulation in microorganisms, the environment, and humans, leading to resistance. Recently, medicinal plants, bioactive compounds, and herbal therapy may be more effective than chemotherapeutics in aquaculture and can contribute to economic sustainability (Tavares-Dias, 2018). Essential oils derived from plants are replacing synthetic drugs and are considered crucial for animal nutrition and health continuity, promoting growth and improving digestion, gut microbiota, growth performance, and welfare. The potential use of these products in aquaculture is known to prevent diseases such as bacterial and parasitic agents, while also being effective against stress (Sutili et al., 2018). Probiotics have been reported to have positive effects on growth performance and the antioxidant system in fish health (Can et al., 2012). Similarly, propolis, a natural bee product, is also considered as an alternative biotherapeutic agent due to its antimicrobial and immunomodulatory properties. Propolis contains a wide variety of biomolecules such as phenols, esters, terpenes, sugars, and minerals, and bioactive compounds such as flavonoids and phenolic acids are closely related to its biological activity. Specific components such as caffeic acid, gallic acid, kaempferol, quercetin, and pinosembrin contribute to its functional properties and provide important information about the normalizing and therapeutic effects of propolis (Farag et al., 2021). With over 300 components, it contains antibacterial, antiviral, antifungal, antiparasitic, anti-inflammatory, immune-stimulating, and antitumor properties. It has been used and found effective in treating various metabolic, infectious, and other diseases in farm animals such as cows, pigs, sheep, goats, and horses, as well as in dogs and cats (Abu-Seida, 2023). On the other hand, propolis has been found to have positive effects on fish growth, feed utilization, and reproduction, improve intestinal health, and, in addition to its antioxidant and anti-inflammatory properties, is also effective against infectious agents (Farag et al., 2021). The aim of this study was to evaluate the biological and therapeutic effects of propolis and its bioactive compounds in fish health, and to reveal their PROPOLIS AS A NATURAL THERAPEUTIC IN SUSTAINABLE AQUACULTURE . . .   121 application potential by reviewing the current literature on the use of propolis in aquaculture, while also discussing future perspectives regarding its benefits and possible limitations. 2. Biological Properties of Propolis and Effects on Animals Health Status Propolis is a waxy resinous substance formed by bees mixing plant secretions with beeswax, pollen, and enzymes, its color varying depending on its source. Bees use propolis to insulate and seal their hives and protect them against pathogens such as bacteria and fungi (de la Cruz-Cervantes et al., 2018). It exhibits antiviral, antifungal, and antiparasitic properties (Sforcin, 2007). The major components found in propolis also vary depending on its geographical origin. However, it generally contains phenolic acids, flavonoids, and terpenoids, which have positive pharmacological effects on health and contribute to the biological properties of propolis (Zabaiou et al., 2017). At the same time, propolis, which contains resin wax, essential oils, and pollen, has been shown to exhibit antitumor activity in studies. In particular, in vitro studies using cancer cell lines are especially common (Sepúlveda et al., 2020). Incorporating propolis into the feed or food of various animals has been shown to promote growth and have positive effects on the immune system. It has also demonstrated antimicrobial and antioxidant properties. Cécere et al., (2021) found that when propolis was mixed into the milk of lactating lambs and administered to them, it increased growth and immune response while reducing the total coliform and E. coli counts in feces. Currently, propolis, which can regulate rumen fermentation and particularly affects gram-positive bacteria, offers a natural feed alternative to antibiotics in ruminant diets. It also has beneficial effects on pregnancy and growth, as well as on sperm motility and production in males (Soltan et al., 2016). A meta-analysis has shown that bee pollen and propolis are natural growth promoters for rabbits, increasing weight gain, reducing the feed conversion ratio, and exhibiting antioxidant properties, but they do not affect kidney or liver health levels (Sierra-Galicia et al., 2023). In the treatment of toxoplasmosis, a protozoal disease, the synergistic use of propolis with spiramycin increased the activity of spiramycin in vivo, and the best reduction in bradyzoites was observed in rats with chronic toxoplasmosis (Hegazi et al., 2021). 122   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Therefore, due to its biological content, propolis is increasingly being used in livestock and pets for processes such as reproduction, growth, immune system function, feed utilization, and disease treatment, and is considered to be quite effective. 3. Effects and Applications on Fish Health Focusing on the use of natural components such as propolis to increase the production and reproductive performance of different fish species is crucial for aquaculture sustainability. In aquaculture, excess stock density in farms makes fish susceptible to diseases. Environmental stresses negatively affect various systems, while pathogens cause mortality and morbidity. This situation also brings economic losses for farms (Farag et al. 2021). This product is considered a natural additive with the potential to enhance growth performance, support immunity, and provide protection against pathogens in aquaculture (de la Cruz-Cervantes et al., 2018). Propolis is frequently used by adding it to fish feed. Its use in sea bream, catfish, sea bass, nile tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss), carp (Cyprinus carpio), turbot (Scophthalmus maximus), and eel has demonstrated antiviral, antimicrobial, and anti-inflammatory effects, and growth-promoting effects have been found. While improving intestinal health, it has shown liver-protective and hypoglycemic effects. It also has positive effects on reproductive performance (Farag et al. 2021). Propolis, thanks to the phenolic and flavonoid compounds it contains, also exhibits antifungal effects in fish health, disrupting cell wall integrity to inhibit mycelium growth and playing a supportive role in the immune response (Doğan et al., 2025). Below is a table summarizing optimum application doses and biological effects of propolis obtained from studies conducted on its use in fish diseases. The table includes fish species, pathogenic agent, propolis type, administration route, observed effects, and their references (Table 1). PROPOLIS AS A NATURAL THERAPEUTIC IN SUSTAINABLE AQUACULTURE . . .   123 Table 1. The use of propolis in fish diseases, some studied pathogenic agents, application route and effects Fish Species Type of propolis Studied pathogen Application method or assay Effects References Nile tilapia (Oreochromis niloticus) Dietary propolis and turmeric (mixture %1-%1) Edwardsiella tarda Dietary supplementation Growth and immune responses↑ (Edrees et al., 2025) Common carp (Cyprinus carpio) Crude propolis (T1) and water-ethanol extract propolis (WEEPT2,T3,T4) Aeromonas hydrophila Dietary supplementation ↑ Albumin in crude propolis group; ↑ Glucose in WEEP groups ↔ Spleen somatic index in T3 ↔ Cholesterol ↔ NBT (nitro blue tetrazolium) activity (Al-Gburi & Mustafa, 2025) Channel Catfish (Ictalurus punctatus) Brazilian red, brown and green propolis Edwardsiella ictaluri and Flavobacterium covae, In vitro assay Activity and efficacy against F. covae ↑ E. ictaluri ↔ (Ribeiro et al., 2024) Common carp (Cyprinus carpio) Crude propolis T1 (10 g/kg ) and Water Ethanol Extract propolis (WEEP-2, 4, 8 g/kg diet-T2, T3, T4) Aeromonas hydrophilia Dietary supplementation At 2 g/kg WEEP: ↑ WBC count, ↑ RBC, ↑ Hb and PCV Interleukin-1β (IL-1β) gene expression ↓ (in T2 compared to T3) Crude propolis (10 g/kg) caused ↓ RBC, Hb, PCV due to high wax content (Al-Gburi et al., 2024) NM: This information has non-mentioned in referenced article; ↑:Effective, increasing; ↓:Ineffective, reducing; ↔ :No significant differences or effects Notes: Aspartate aminotransaminase (AST), alanine aminotransferase (ALT), creatinine (CRE), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH), NBT (nitro blue tetrazolium) activity. 124   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I Table 1. Continue Fish Species Type of propolis Studied pathogen Application method or assay Effects References Common carp (Cyprinus carpio) Dietary propolis Flavobacterium columnare Dietary supplementation Pathogenic bacteria cells adherent to the fish gills ↓ Growth performance ↑ Physiological profile ↑ Health status ↑ AST, ALT, CRE, ALP, LDH ↑ (Hassanien et al., 2023) Turbot (Scophthalmus maximus) NM and Not specified (general propolis, dietary supplementation) Edwardsiella piscicida Dietary supplementation ↑ Anti-oxidative stress enzymes (SOD, CAT, GPT); ↑ Cytokines (IL-1β, IL-6, TNF-α); ↓ histopathological damage; ↓ bacterial load; ↑ survival (Mu et al., 2022) NM: This information has non-mentioned in referenced article; ↑:Effective, increasing; ↓:Ineffective, reducing; ↔ :No significant differences or effects Notes: Aspartate aminotransaminase (AST), alanine aminotransferase (ALT), creatinine (CRE), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH), NBT (nitro blue tetrazolium) activity. 4. Challenges and Limitations Since ancient times, dating back to 300 BC, propolis can vary in color from green to red and dark brown, and although it has no toxic or side effects, it can sometimes cause allergies and contact dermatitis in humans (Sforcin, 2007). Although propolis is recognized in the literature as a promising natural product for fish health, there is no official approval or regulation for its use in aquaculture by international authorities such as the World Health Organization (WHO) or FAO/Codex Alimentarius. The ratios of biological components in propolis vary depending on the geographical region, so there is no standard procedure. The lack of standard dosage and protocol makes it difficult to develop effective treatment methods. The biggest obstacles to commercialization are high chemical diversity, collection time, the activity of the solvent used, and the presence of beeswax contaminants (de la Cruz-Cervantes et al., 2018). 5. Future Perspectives & Conclusion The use of natural bioactive substances and phytotherapy applications in aquaculture has gained increasing importance in recent years in terms of PROPOLIS AS A NATURAL THERAPEUTIC IN SUSTAINABLE AQUACULTURE . . .   125 reducing the need for antibiotics and synthetic chemicals and limiting the overuse of resistant organisms. Among these natural alternatives, propolis stands out due to its antimicrobial, antifungal, antiparasitic, antioxidant, and immunomodulatory properties, as well as its numerous bioactive compounds derived from bees. Current literature indicates that propolis, when used as a feed additive or applied directly, can improve growth performance in fish, strengthen the immune system, and reduce pathogen-related mortality. However, there are some gaps and challenges regarding its use in safe and sustainable aquaculture practices. One of the most significant issues in the use of propolis is the variability of its chemical composition. As with other plant-based natural products, factors such as geographical origin, source, and extraction method affect the amounts of bioactive compounds, particularly flavonoids and phenolic acids. This variability leads to inconsistent results across studies and complicates standardization. Future research should focus on developing reliable quality control systems and chemical characterization protocols for propolis-based products. Such standardization is critical for both the regulatory approval process and the widespread adoption of commercial applications. However, the dosage, application strategies, and species-specific methods need to be optimized. Although various studies have reported the positive effects of propolis use at different concentrations and in different fish species, the results are not always consistent. This situation demonstrates the need to clearly define species-specific dosage ranges and application methods. Furthermore, the synergistic effects that may arise from the combined use of propolis with other natural products (probiotics, plant extracts, etc.) and certain drugs have largely not been researched, and future studies are needed in this area. From an ecological and sustainable aquaculture perspective, propolis offers clear advantages due to its non-accumulation in nature and low toxicity. It is an environmentally friendly alternative to antibiotics and chemicals. As a result, propolis is considered a highly promising product that can support fish health by enhancing growth performance, regulating the immune response, and providing resistance to diseases. However, for this potential to be transferred to fish farms in routine applications, issues such as chemical variability, dosage optimization, and long-term safety need to be clarified. The development of specific formulations and applications is crucial. 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Biological properties of propolis extracts: Something new from an ancient product. Chemistry and physics of lipids, 207, 214-222. https://doi.org/10.1016/j.chemphyslip.2017.04.005 THE ROLE OF FRESHWATER SNAILS IN ADVANCING SUSTAINABLE . . .   135 3.1. Wastewater treatment processes The most appropriate treatment method must be selected to achieve targeted decontamination levels when water contamination occurs, and water needs to be cleaned. The treatment process starts from the preliminary treatment stage, which is usually carried out by physical and mechanical methods, and moves to the primary treatment by physico-chemical and chemical processes. Secondary treatment is then carried out using chemical and biological methods. Following this stage, tertiary treatment is applied through physical and chemical processes. Finally, sludge is treated as part of the clarification process; this can either be disposed of in a controlled manner, recycled or incinerated. The first two stages are often considered together as pre-treatment or initiator steps (Anjaneyulu et al., 2005). In water treatment, pre-treatment involves first removing (floating) solid particles and all suspended matter from the wastewater. This process can be done by physical or mechanical means and is a step that must be carried out before the secondary purification stage. Because particle contamination, such as suspended solids (SS), colloids, oils, etc., can reduce the effectiveness of subsequent treatment processes or harm the decontamination process. Additionally, primary chemical processes such as oxidation and chromium(VI) reduction, pH adjustments, and prior removal of high organic loads may also be necessary to eliminate cyanide. For example, wastewater from paper mills contains large amounts of suspended solids (SS) such as fibers, fillers and other solid particles (Pokhrel and Viraraghavan, 2004; Anjaneyulu et al., 2005; Sharma, 2015). In addition, wastewater from textile factories is generally alkaline and contains high organic loads, although their pH is quite variable. For this reason, this wastewater must be pre-treated before secondary treatment. However, in most cases, these processes alone are not sufficient to meet the requirements of the legislation. To fully eliminate chemical contaminants from wastewater before it is discharged into the environment or repurposed, it must undergo secondary treatment employing the most suitable biological, physical, or chemical methods available. In some cases, tertiary treatment may be required to remove byproducts such as pollutants remaining during the secondary treatment process or salts formed as a result of mineralization of organic matter. In Europe, tertiary treatment is not common, although this process may become necessary in the future with new environmental regulations. Currently, tertiary treatment methods commonly used in industrial facilities include adsorption with activated carbon, 136   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I ion exchange, membrane filtration (ultrafiltration, reverse osmosis), advanced oxidation and artificial wetlands (CW). Although artificial wetlands are widely used especially in domestic wastewater treatment and municipal sewage, they are also effectively applied in the treatment of industrial wastewater, such as leather industry waste or water generated after paper production, thanks to various configurations. 3.2. Wastewater treatment technologies Conventional wastewater treatment uses a combination of physical, chemical and biological processes to remove solids from wastewater. These processes are applied to remove many different types of pollutants such as colloids, organic compounds, nutrients and soluble pollutants. Traditional methods involve the use of a variety of techniques, including both currently used recovery processes and newly developed removal techniques. The method to use will be determined according to the characteristics of the wastewater (Anjaneyulu et al., 2005; Crini, 2005; Cox et al., 2007). Each treatment method must be evaluated not only in terms of cost, but also considering different factors such as efficiency, feasibility, applicability, reliability, environmental impacts, sludge production, operational difficulties, pre-treatment requirements and the emergence of potentially toxic by-products. However, most of the various wastewater treatment methods available today are widely used in the industrial sector simply because they are technologically and economically feasible. While the removal of pollutants from wastewater is generally achieved by physicochemical and/or biological processes, research focuses on developing lower-cost and effective system combinations or new alternative methods. 4. USE of FRESHWATER SNAILS in WASTEWATER TREATMENT Freshwater snails feed on algae, macrophytes and detritus, which are food sources in aquatic ecosystems, and are hunted by many predatory species. This balance puts them at a vulnerable point in food webs (Brönmark 1989; Covich 2010). Watton and Hawkes (1984) examined the population densities, biomass, growth rates and reproductive rates of Lymnaea peregra (Müller) and Potamopyrgus jenkinsi (Smith) over a 21-month period in three experimental earthen canals, where one canal carried clean river water and the other two canals carried 25% and 50% treated sewage, respectively. While the wastewater THE ROLE OF FRESHWATER SNAILS IN ADVANCING SUSTAINABLE . . .   137 mixed with the river water, each channel was divided into different pool areas, and it was determined that the abundance and biomass of both species were higher in the channels. Density and biomass of L. peregra increased significantly in grooves containing wastewater, but the concentration of wastewater had no significant effect on density or biomass (P < 0.01). Density and biomass of P. jenkinsi were found to be significantly higher in ponds without wastewater (P < 0.001), and the channel carrying 25% wastewater was reported to have greater abundance and biomass than the channel carrying 50% wastewater (P < 0.05). No significant difference in the growth rate of L. peregra was observed between channels. In ponds with wastewater, the average number of eggs laid an egg mass by L. peregra increased significantly, resulting in more mass and eggs in the 50% wastewater channel compared to the 25% wastewater channel (P < 0.01). No significant difference was observed in the reproduction rate of P. jenkinsi per adult between channels carrying 0% and 25% wastewater. Cannicci (2009) investigated the differences in macrobenthos communities in mangrove ecosystems in urban areas and in areas not affected by sewage effluents in East Africa. Evaluated differences observed in epifaunal communities of crabs and molluscs using multivariate ACI unbalanced analyzes to compare peri-urban mangrove swamps with non-urban mangroves with similar ecological characteristics. The sampling design was spatially nested, with samples collected in equatorial (southern Kenya) and subtropical (southern Mozambique) regions. The findings of the study revealed a steady increase in crab biomass in urban areas in both regions. It also showed that peri-urban mangrove systems are richer than non-urban mangroves with fiddler crabs (Uca spp.) feed on benthic microalgae and bacteria, and sesarmids such as Perisesarma guttatum and Neosarmatium meinerti feeding on both species. However, a significant decrease in the abundance of gastropods has been observed, especially in Kenya, due to the disappearance of the mud snail Terebralia palustris. In conclusion, these findings revealed detectable effects of domestic wastewater on crabs and molluscs in East African mangrove systems and how these can be used as biological indicators to indicate environmental impacts in mangroves. Furthermore, changes in benthic structures in peri-urban areas indicate the need to further investigate the capacity of natural mangrove forests to absorb pollution from sewage treatment. Mollusc species are sensitive to various endocrine disrupting compounds (EDCs) in their environment, and the concentrations of these compounds can affect the life processes of these species. Wastewater treatment plants (WWTPs) 138   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I are a significant source of potential or known EDCs in aquatic environments. Gust et al. (2010), using the New Zealand mud snail Potamopyrgus antipodarum (Mollusca, Hydrobiidea), aimed to develop a field exposure method to evaluate the effects of water quality on the habitat characteristics of this species, especially its effects on reproduction. The research examined the effects of WWTP discharges in three different receiving rivers. The snails’ survival rate, weight, reproductive activity, and levels of vertebrate-like sex hormones were tracked and analyzed over a period of three to four weeks. Although there is considerable variability in the physicochemical and hydrological characteristics of rivers, caging studies have shown that wastewater treatment plant (WWTP) effluents lead to significant disruptions in the habitats of snails further downstream. Adult survival was found to be unaffected by exposure, but reproduction in the area of WWTP wastewater discharges was found to be significantly reduced (a 60-70% reduction in the number of unshelled embryos after three to four weeks). Changes in steroid levels showed that testosterone levels increased downstream of the discharges and 17β-estradiol levels increased or decreased depending on the region. These findings suggest that steroid levels are an important biomarker and that observations using endpoints adapted for field exposures enable discrimination between different sites. Shen et al. (2020) conducted a 350-day long-term flow test using the freshwater snail Bellamya aeruginosa, a benthic macroinvertebrate, in which they examined the bioturbation effect on the control of phosphorus (P) pollution in sediment with drinking water treatment residue (DWTR). Research results have revealed that DWTR significantly reduces the phosphorus concentration of overlying water but has limited impact on other water properties and tends to reduce nitrogen release from sediment. They determined that changes in overlying water properties caused by DWTR were not directly related to freshwater snail activity or population density. However, they emphasized that snails promote the burial of DWTR and mobilize DWTR mixing in the sediment, which may change the distribution of phosphorus neutralizing substances in the sediment through bioturbation. The mobility of phosphorus is closely related to the oxalate-extractable aluminum, iron and phosphorus contents at different depths of sediments. In the study, it was observed that mobile phosphorus is stable at a lower level when the total content of aluminum and iron oxides exceeds 0.750 mmol g−1 or when the ratio of phosphorus oxide to aluminum and iron oxides falls below 0.05. In particular, for DWTR, which are Al and Fe-based agents, they noted that the associations of mobile phosphorus in THE ROLE OF FRESHWATER SNAILS IN ADVANCING SUSTAINABLE . . .   139 the sediment with phosphorus oxide, aluminum and iron oxides necessitated repeated dosing of immobilizing agents. Consequently, they suggested that the impact of bioturbation on the stability of in situ phosphorus immobilization in sediments should be considered in the context of long-term pollution control. Subba et al. (2021) evaluated the effects of Potamopyrgus antipodarum grown in a laboratory environment against pollutants resulting from various land use activities and to what extent these pollutants can indicate the degree of pollution in freshwater ecosystems. The effects of pollutants from runoff and direct discharges in Merri Creek on both organism-level parameters (survival, growth, and reproduction) and sub-organism-level markers (including lipid peroxidation (LPO) and glutathione S-transferase (GST) activity) were investigated in their study The research observed enzyme activities in snails (including catalase (CAT)) over a 28-day exposure period in samples taken from nine different sites in Merri Creek and one site in Cardinia Creek. The top two areas in Merri Creek were designated as reference areas minimally affected by human activities, while the remaining areas were selected as impact areas under the influence of various anthropogenic land uses. The study found that P. antipodarum has the potential to be a sensitive bioindicator in Australian conditions and responds to varying contaminant concentrations resulting from different land use activities. It was also emphasized that this species exhibited similar sensitivity to P. antipodarum and other biomarkers found in other regions worldwide. Panda et al. (2022) emphasized that Pila globosa, a semi-sessile, ectothermic and amphibious mollusc, has not been adequately examined in terms of environmental factors. In order to better understand the ecological role and ecotoxicological and physiological responses of the organism to environmental stress factors, basic information about metabolic events, including inactive periods such as pollution and hibernation, needs to be revealed. In their study, the ecotoxicological and physiological responses of P. globosa to various non-living and living environmental stressors, such as toxic metals, organophosphates, carbamate pesticides, and butachlor, were analyzed. It has been investigated in relation to factors such as energy expenditure, fat metabolism during sedentary periods, and dehydration. Additionally, in order to better understand the relationship of environmental factors with metabolic processes, oxidative stress, respiratory and antioxidant enzyme activities, carbohydrate metabolism and the activities of neurotransmitter enzymes such as acetylcholinesterase were examined. The various enzymatic activities observed in this organism 140   SUSTAINABLE PRACTICES ON AQUATIC SCIENCES I under chemical exposure indicate that P. globosa can be used as a biomarker in ecotoxicological studies in freshwater ecosystems. For example, body carbohydrate and protein contents increased by 32% and 37% during feeding. Additionally, during periods of inactivity, there was a significant reduction in the activity of key enzymes, with adenosine monophosphate deaminase, adenosine deaminase, succinic dehydrogenase, cytochrome-c-oxidase, and glutamate dehydrogenase decreasing by 75.5%, 62.6%, 54%, 59%, and 62%, respectively. As a result, it was stated that P. globosa could be a reliable ectothermic model for monitoring freshwater environments. 5. CONCLUSIONS The entry of chemical pollutants into water bodies and their negative effects on aquatic organisms pose a major threat to sustainable environmental management. Sustainability is directly linked to preserving the health and biodiversity of ecosystems, highlighting the critical importance of maintaining the health of aquatic ecosystems. Pollutants such as wastewater, industrial effluents, agricultural and oil spills can contaminate aquatic environments, negatively impacting ecosystem services and threatening the sustainability of these ecosystems. Maintaining the health of aquatic ecosystems is essential not only to address current environmental threats, but also to ensure the long-term viability. In this context, understanding the effects of water pollution on ecosystems is a fundamental elements of sustainable water management. Environmental risk assessments, particularly field studies, can help develop strategies to ensure the sustainability of aquatic ecosystems by monitoring how aquatic organisms respond to pollutants. Organisms such as molluscs can serve as bioindicators, providing effective tools for monitoring water quality. By simulating scenarios where pollution is temporary or intermittent, such field studies help us more accurately understand real-world effects that cannot be observed under laboratory conditions. Sustainable water management is necessary to mitigate the effects of these pollutants and maintain the balance and functionality of ecosystems. By measuring the effects of pollution, these studies enable better management of natural resources and preserve the health of aquatic ecosystems for future generations. Therefore, understanding environmental risks forms the foundation for steps to be taken toward a sustainable environment. 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