Zooplankton abundance and environmental variables at weathership station India, 59oN 19oW, from 1974 to 1975

DATA NOTE Zooplankton abundance and environmental variables at weathership station India, 59o N 19o W, from 1974 to 1975 [version 1; peer review: 1 approved with reservations] Xabier Irigoien 1,2 1AZTI - BRTA, Pasaia, Euskadi, Spain 2Ikerbasque, Bilbao, Basque Country, Spain First published: 10 Sep 2025, 5:277 https://doi.org/10.12688/openreseurope.21298.1 Latest published: 07 Oct 2025, 5:277 https://doi.org/10.12688/openreseurope.21298.2 v1 Abstract This dataset was collected between 1971 and 1975 at Weathership Station India (59°N, 19°W) in the North Atlantic Ocean. It comprises quantitative records of several zooplankton taxa—Calanus finmarchicus, Metridia lucens, Pleuromamma robusta, Oithona spp., Oncaea spp., and Acartia spp.—alongside measurements of phytoplankton abundance, temperature, salinity, chlorophyll a concentration, Secchi depth, and primary production. Sampling frequency and depth resolution varied by parameter. The dataset is organized into separate Excel files for each variable. Keywords Zooplankton, vertical distribution, North Atlantic, ocean time series This article is included in the Earth and Environmental Sciences gateway. This article is included in the Horizon 2020 gateway. Open Peer Review Approval Status 1 version 2 (revision) 07 Oct 2025 view version 1 10 Sep 2025 view Taketoshi Kodama , The University of Tokyo, Bunkyo, Japan 1. Any reports and responses or comments on the article can be found at the end of the article. Open Research Europe  Page 1 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025 Corresponding author: Xabier Irigoien ([email protected]) Author roles: Irigoien X: Conceptualization, Data Curation, Funding Acquisition, Investigation, Project Administration, Writing – Original Draft Preparation, Writing – Review & Editing Competing interests: No competing interests were disclosed. Grant information: This work was supported by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 817806 (Sustainable Management of Mesopelagic Resources, SUMMER). Copyright: © 2025 Irigoien X. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite this article: Irigoien X. Zooplankton abundance and environmental variables at weathership station India, 59 o N 19 o W, from 1974 to 1975 [version 1; peer review: 1 approved with reservations] Open Research Europe 2025, 5:277 https://doi.org/10.12688/openreseurope.21298.1 First published: 10 Sep 2025, 5:277 https://doi.org/10.12688/openreseurope.21298.1 Open Research Europe  Page 2 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025 Introduction The vertical structure and transport processes in open-ocean ecosystems represent a significant knowledge gap in our understanding of global biogeochemical cycles (Martin et al., 2020). Despite their importance, vertically resolved biological datasets from the open ocean remain scarce, primarily due to the logistical and financial constraints associated with long-term ship-based observations. Consequently, seasonal dynamics of vertical ecosystem structure are poorly characterized. While autonomous platforms are expected to address this limitation in the future, current biological data from such systems remain limited in scope and resolution. Between the 1970s and 1990s, weather ships stationed in the open ocean provided continuous meteorological data for forecasting purposes. These vessels also offered unique opportunities for oceanographic sampling (e.g., Batchelder, 1985; Irigoien et al., 1998; Irigoien, 1999; Irigoien & Harris, 2006; Mackas et al., 1998). The data collected during these campaigns offer rare insights into seasonal variability in oceanic ecosystems as well as serving as historical baselines for climate change studies. However, much of this information remains difficult to access. One such dataset was acquired at Weathership Station India (59°N, 19°W) between 1971 and 1975 (Williams & Hopkins, 1971; Williams & Hopkins, 1975a). Portions of this dataset were later recovered under the Plankton Reactivity in the Marine Environment (PRIME) project and archived in the British Oceanographic Data Centre (BODC). However, the fragmented format—one file per species and sampling date—has hindered its usability. As part of the European Union Horizon 2020 project Sustainable Management of Mesopelagic Resources (SUMMER, Grant No. 817806), these data have now been consolidated into accessible formats. This paper presents the dataset and aims to promote its use in ecological related research. Materials and methods Sampling was conducted from 1971 to 1974 at Weathership Station India, located approximately 260 nautical miles south of Iceland on the western slope between the Hatton Bank and the Iceland Basin, at a depth of ~2000 m. The region is characterized by a deep mixed layer during winter (September–March) due to strong wind forcing, followed by stratification during calmer periods. The sampling period was characterized by the passage of the great salinity anomaly (1968–1982, Dickson et al., 1988). Sampling methodologies are detailed in Williams (1988) and Irigoien (2000). In brief, vertical distributions of copepods were assessed weekly from March to October using oblique tows with a Longhurst-Hardy Plankton Recorder (280 µm mesh). Tows were designed to sample every 10 m from 500 m to the surface. Hydrographic profiles (temperature and salinity) were obtained approximately every five days at 19 discrete depths from the surface to 2000 m. Chlorophyll a concentration was measured from water samples collected at 10 depths (0–200 m) approximately every two days. According to the records the method used to measure Chl a was described by Adams and Baird in Annls. biol., Copenh., 26: 113–114. We could not find that complete description, but after further research Chl a was most likely measured using the Yentsch and Menzel (1963) method. Basically, Samples for analysis of photosynthetic pigments were collected by filtration through Whatman GF/C glass fiber filters, frozen until assayed, extracted with 90% v/v acetone and measured by fluorometry using and Turner fluorometer). Primary production was measured through 14C incubations following Strickland and Parsons (1968) where a known amount of radioactive carbonate 14CO3 is added to the sea water sample and incubated for a determined period. After incubation samples are filtered, washed and dried, and the radioactivity from the 14CO3 assimilated by phytoplankton measured using a scintillation counter. We could not find the detailed methodology for the phytoplankton taxonomic identification. However, it can be assumed that samples were fixed in 1% lugol and counted under an inverted microscope after settling Utermohl technique, following an approach like Holligan and Harbour (1977). Secchi (Secchi, 1864) depth is a measure of water clarity, determined by the depth at which a black and white disk (Secchi disk) disappears when lowered into the water. The Secchi disk, typically a 30 cm white disk with alternating black and white quadrants, is attached to a rope. The observer records the depth at which the disk can no longer be seen is recorded as the Secchi depth. It is a widely used technique, but attention should be paid in the file to the notes about cable angles and state of the sea that bias the measurements. Data description The dataset is publicly available via Zenodo (https://doi. org/10.5281/zenodo.15862644), (Irigoien, 2025) under a Creative Commons Attribution 4.0 International license. It includes six Excel files corresponding to the following parameters: chlorophyll a (Chlorophyll a.xlsx), zooplankton taxonomic abundance (India all copepods m3.xlsx), phytoplankton taxonomic abundance (Phytoplankton.xlsx), primary production (Primary production. xlsx), Secchi depth (SECCHI depth.xlsx), and temperature and salinity (Temperature and Salinity.xlsx). Although historical records indicate that additional data (e.g., nutrients, euphausiids, amphipods, jellyfish) were collected (Williams & Conway, 1981; Williams & Hopkins, 1975b; Williams & Lindley, 1982; Williams & Robins, 1981), these data was not recovered by the PRIME project. The zooplankton dataset includes abundance data for Calanus finmarchicus, Metridia lucens, Pleuromamma robusta, Oithona spp., Oncaea spp., and Acartia spp. Users should exercise caution when interpreting Acartia data, as inconsistencies exist between total and stage-specific counts due to changes in stage classification across original files. Similarly, phytoplankton data should be interpreted with care. Although the methodology is undocumented, it is presumed that samples were preserved with Lugol’s solution and analyzed microscopically following sedimentation, as described in Irigoien et al. (2000). The accuracy of species-level identification may vary depending on the analyst, and it is unclear whether all samples were processed by Page 3 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025 the same individual. Therefore, while data for major groups (e.g., diatoms, dinoflagellates, coccolithophores) are likely reliable, species-level presence/absence data should be treated with caution. Ethics and consent Ethical approval and consent were not required. Data availability The dataset is publicly available via Zenodo Zenodo: Weathership India 1971–1975 mesozooplankton and additional environmental data (https://doi.org/10.5281/zenodo. 15862644), (Irigoien, 2025). It includes six Excel files corresponding to the following parameters: - Chlorophyll a.xlsx: Chlorophyll a measurement in mg Chl a m-3, - India all copepods m3.xlsx: zooplankton taxonomic abundance (Calanus finmarchicus, Metridia lucens, Pleuromamma robusta, Oithona spp., Oncaea spp., and Acartia spp.) in ind m-3 - Phytoplankton.xlsx: Phytoplankton taxonomic abundance in cell l-1 - Primary production.xlsx: primary production in C14 uptake mg C.m-3.day-1 - SECCHI depth.xlsx: Secchi depth in m - Temperature and Salinity.xlsx: temperature and salinity in °C and ppt. Data is available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0). Acknowledgments Special thanks are due to R.P. Harris for his foresight to recover this data set during the PRIME project and make it available. Particular thanks are also due D.V.P. Conway for his help to understand the structure of the original files. References Batchelder HP: Population dynamics and feeding ecology of the copepod, metridia pacifica, in the subarctic pacific Ocean. Oregon State University, 1985. Dickson RR, Meincke J, Malmberg SA, et al.: The “great salinity anomaly” in the Northern North Atlantic 1968-1982. Progr Oceanogr. 1988; 20(2): 103–151. Publisher Full Text Holligan PM, Harbour DS: The vertical distribution and succession of phytoplankton in the western English Channel in 1975 and 1976. J Mar Biol Ass UK. 1977; 57(4): 1075–1093. Publisher Full Text Irigoien X: Vertical distribution and population structure of. Deep Sea Res. 1999; 47: 1–26. Irigoien X: Vertical distribution and population structure of Calanus finmarchicus at station India (59°N , 19°W) during the passage of the great salinity anomaly, 1971–1975. Deep Sea Res 1 Oceanogr Res Pap. 2000; 47(1): 1–26. Publisher Full Text Irigoien X, Harris RP: Comparative population structure, abundance and vertical distribution of six copepod species in the North Atlantic: evidence for intraguild predation? Mar Biol Res. 2006; 2(4): 276–290. Publisher Full Text Irigoien X, Harris RP, Head RN, et al.: North Atlantic oscillation and spring bloom phytoplankton composition in the English Channel. Journal of Plankton Research. 2000; 22(12): 2367–2371. Publisher Full Text Irigoien X, Head R, Klenke U, et al.: A high frequency time series at weathership M, Norwegian sea, during the 1997 spring bloom: feeding of adult female Calanus finmarchicus. Mar Ecol Prog Ser. 1998; 172: 127–137. Reference Source Irigoien X: Weathership India 1971-1975 mesozooplankton and additional environmental data. [Data set], Zenodo. 2025. http://www.doi.org/10.5281/zenodo.15862644 Mackas DL, Goldblatt R, Lewis AG: Interdecadal variation in developmental timing of Neocalanus plumchrus populations at Ocean Station P in the subarctic North Pacific. 1998; 55(8). Publisher Full Text Martin A, Boyd P, Buesseler K, et al.: The oceans’ twilight zone must be studied now, before it is too late. Nature. 2020; 580(7801): 26–28. Publisher Full Text Secchi PA: Relazione delle esperienze fatte a bordo della pontificia pirocorvetta l’Immacolata concezione per determinare la trasparenza del mare; Memoria del P. A. Secchi. Nuovo Cimento. 1864; 20(1): 205–238. Publisher Full Text Strickland JDH, Parsons TR: A practical handbook of seawater analysis. Bull Fish Res Bd Can. 1968; 167: 328. Reference Source Williams R: Spatial heterogeneity and niche differentiation in oceanic zooplankton. Hydrobiologia. 1988; 167–168(1): 151–159. Publisher Full Text Williams R, Conway DVP: Vertical distribution and seasonal abundance of Aglantha digitale (O.F. Müller) (Coelenterata: Trachymedusae) and other planktonic coelenterates in the northeast Atlantic Ocean. J Plankton Res. 1981; 3(4): 633–643. Publisher Full Text Williams R, Hopkins CCE: Sampling at OWS INDIA (59° 00′N 19° 00′W) in 1971. Annales Biologiques. 1971; 57–60. Williams R, Hopkins CCE: Sampling at OWS INDIA (59° 00′N 19° 00′W) in 1973. Annales Biologiques. 1975a; 30: 60–62. Reference Source Williams R, Hopkins CCE: Sampling at OWS INDIA (59° 00′N 19° 00′W) in 1974. Annales Biologiques. 1975b; 31: 57–60. Williams R, Lindley JA: Variability in abundance, vertical distribution and ontogenetic migrations of Thysanoessa longicaudata (Crustacea: Euphausiacea) in the North-Eastern Atlantic Ocean. In: Marine biology. Springer-Verlag, 1982; 69(3): 321–330. Publisher Full Text Williams R, Robins D: Seasonal variability in abundance and vertical distribution of Parathemisto gaudichaudi (Amphipoda: Hyperiidea) in the North East Atlantic Ocean. 1981; 4: 289–98. Reference Source Yentsch CS, Menzel DW: A method for the determination of phytoplankton chlorophyll and phaeophytin by fluorescence. Deep Sea Research and Oceanographic Abstracts. 1963; 10(3): 221–231. Publisher Full Text Page 4 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025 Open Peer Review Current Peer Review Status: Version 1 Reviewer Report26 September 2025 https://doi.org/10.21956/openreseurope.23034.r60456 © 2025 Kodama T. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Taketoshi Kodama The University of Tokyo, Bunkyo, Japan The manuscript entitled “Zooplankton abundance and environmental variables at weather station India, 59°N 19°W, from 1974 to 1975” by Xabier Irigoien et al. was submitted as a data note. The dataset is highly valuable, and I therefore recommend indexing of this data note after revision. Since the dataset itself constitutes the results, and no formal results or discussion sections are expected, my comments are limited to minor revisions regarding consistency and formatting. 1. Title and text consistency  • Please revise the title. I believe the dataset covers the years 1971 to 1975, not 1974 to 1975.  • Similarly, the first sentence of the Materials and Methods should be corrected from “Sampling was conducted from 1971 to 1974” to “Sampling was conducted from 1971 to 1975.” 2. Zenodo files  • The files in Zenodo should be revised for consistency. In particular, columns for year, month, day, and time should be included in every file. For example, “9h” alone is insufficient information. Harmonized datasets with standardized column headers will greatly facilitate future metaanalyses.  • In the file India all copepods m3.xlsx, please clarify the meaning of “mid-depth.” The statement “Tows were designed to sample every 10 m from 500 m to the surface” does not provide sufficient information for interpretation. If sampling ranges were recorded, they should be explicitly noted in the Excel file.  • Please avoid using abbreviations for genus names. For example, “Cerat. Furca” may refer to Ceratium furca, but this is unclear. Similarly, “Boto” may indicate Boto spp. (given that Fragilaria spp. are mentioned). If abbreviations are intentional, please provide an explanation. In sum, the dataset represents a highly valuable long-term record, and with these minor corrections, it will provide a robust and reusable resource for the community. Is the rationale for creating the dataset(s) clearly described? Yes Are the protocols appropriate and is the work technically sound? Open Research Europe  Page 5 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025 Yes Are sufficient details of methods and materials provided to allow replication by others? Yes Are the datasets clearly presented in a useable and accessible format? Partly Competing Interests: No competing interests were disclosed. Reviewer Expertise: Oceanography I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Author Response 01 Oct 2025 Xabier Irigoien 1. Title and text consistency  • Please revise the title. I believe the dataset covers the years 1971 to 1975, not 1974 to 1975. Corrected in the new version  • Similarly, the first sentence of the Materials and Methods should be corrected from “Sampling was conducted from 1971 to 1974” to “Sampling was conducted from 1971 to 1975.” Corrected in the new version. 2. Zenodo files  • The files in Zenodo should be revised for consistency. In particular, columns for year, month, day, and time should be included in every file. For example, “9h” alone is insufficient information. Harmonized datasets with standardized column headers will greatly facilitate future meta-analyses. A new file with additional 4 columns has been created and added to Zenodo. The new columns containday, month, year and hour (when available). Some other files without information have been cleaned out.The previous file has been maintained in zenodo as it has been downloaded by different people and I believe is important they can find the original file. The changes are reported in the new version.  • In the file India all copepods m3.xlsx, please clarify the meaning of “mid-depth.” The statement “Tows were designed to sample every 10 m from 500 m to the surface” does not provide sufficient information for interpretation. If sampling ranges were recorded, they should be explicitly noted in the Excel file. Sampling ranges were not available in the original files, only the mid-depth of the range. Because of the sampling design it can be assumed that the range is more or less 5 m above and below the mid depth. But the detailed information was not available.  • Please avoid using abbreviations for genus names. For example, “Cerat. Furca” may refer to Ceratium furca, but this is unclear. Similarly, “Boto” may indicate Boto spp. (given that Fragilaria spp. are mentioned). If abbreviations are intentional, please provide an explanation. The abbreviations is the only information available in the original file. They could be interpreted but as it is not possible to validate with the originator for the dubious cases I think is better to keep the original information and reinforce the message about being cautious using the Open Research Europe  Page 6 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025 species level. The alternative would be to eliminate the phytoplankton file, but I believe that it contains valuable information although limited at the taxonomic level. In sum, the dataset represents a highly valuable long-term record, and with these minor corrections, it will provide a robust and reusable resource for the community. Competing Interests: No competing interests were disclosed. Open Research Europe  Page 7 of 7 Open Research Europe 2025, 5:277 Last updated: 24 OCT 2025