WOBEC SOP Plankton nets

Weddell Sea Observatory of Biodiversity and Ecosystem Change – WOBEC Standard Operating Procedures Technical Documentation December 2025 To be cited as Lenss, Megan, Nils Van den Steen, Anette Wold, Sebastien Moreau, Karley Campbell, and Anton Van de Putte. ‘WOBEC SOP Plankton Nets’. Zenodo, 15 December 2025. https://doi.org/10.5281/zenodo.17935761. Co-funded by the European Union (c) The authors This report is licensed under the Creative Commons Attribution International license Versions Date Comment Responsible Approved 30 October 2024 SOPs for sampling of zooplankton M. Lenss A. Wold S. Moreau K. Campbell 12/12/2025 Formatting N. Van den Steen Table of Contents 1 Description of sampling gear .......................................................................................................... 3 1.1 WP2 (or other type of ring net) ....................................................................................................... 3 1.2 Macrozooplankton trawl .................................................................................................................... 3 2 Sampling gear deployment .............................................................................................................. 4 2.1 Deployment ............................................................................................................................................. 4 2.1.1 Deployment of the multi net ........................................................................................................... 5 2.1.2 Deployment of Macroplankton trawl /net ................................................................................. 5 2.1.3 Deployment of the WP2 net 180 µm ............................................................................................ 6 2.1.4 Deployment of the phytoplankton net ........................................................................................ 6 2.1.5 Deployment of the on-ice hand net sampling. .......................................................................... 6 2.2 Post-Deployment ................................................................................................................................... 6 2.3 Common Issues ...................................................................................................................................... 7 3 Sample sorting-collection-preservation procedure ............................................................... 7 3.1 Mesozooplankton abundance/taxonomy .................................................................................... 7 3.2 Macrozooplankton abundance/taxonomy .................................................................................. 7 3.3 Mesozooplankton and mesozooplankton stable isotopes .................................................... 8 3.4 Phytoplankton hand net taxonomy ................................................................................................ 8 3.5 On-ice hand net sampling .................................................................................................................. 8 4 Sample analysis method ................................................................................................................... 8 Method responsible: Sebastien Moreau 1 Description of sampling gear Mesozoolankton are sampled with nets deployed using crane, winch, and trawling systems aboard R/V Polarstern. Below is a list and description of the necessary nets. HydroBios Multinet midi, maxi of mammuth (depending on what is available onboard) 180 µm. If no Multinet is available NPI can bring a Multinet Midi Specification midi: Opening 50cm*50 cm = 0.25m2, size of box: 80 cm*90 cm*95 cm, 5 net bags 250 cm long with mesh size of 180 μm, overall length 560 cm. The Multinets are deployed with all net bags closed and the water flowing freely through the frame. The instrument can be lowered to the greatest desired depth. It can either be operated by use of communication cable and deck unit and nets can be opened manually or it can be used off-line by pre-programming it as described below. All measuring data are stored inside the (fixed) internal data memory during the operation and can be read out by a PC when the Multinet is back on board. 1.1 WP2 (or other type of ring net) Specification: WP2 stainless steel ring, diameter 57 cm, net 180 μm mesh size, length 2.6 m The WP2 net is deployed vertically and can be closed at specific depth by use of a messenger if needed. Macrozoolankton are sampled with nets or trawls deployed using crane, winch, and trawling systems aboard R/V Polarstern. Below is a list and description of the necessary nets. 1.2 Macrozooplankton trawl Background info: We wish to sample macrozooplankton to obtain quantitative and qualitative samples of macrozooplankton, particularly for krill, amphipods and shrimps with Rectangular midwater trawl and a UnderIce Trawl. Processing of several samples taken plankton nets will include chemical use. A list of the necessary chemicals and their corresponding parameter is provided below. It is the responsibility of the individual using the chemical and processing the sample to operate in a manner that is safe for themselves, others on the ship, and the environment being sampled. Safety Data Sheets (SDS) should be readily available in the labs and proper chemical storage systems should be decided on and implemented before the cruise, including locked chemical storage cabinets and designated workspaces for radioisotopes. Chemical Parameter Safety consideration Glutaraldehyde Protist taxonomy and flow cytometry Carcinogenic Formaldehyde 20 % Protist taxonomy Carcinogenic and mutagenic Formaldehyd 37 % Zooplankton taxonomy Ethanol Genetic samples Toxic Strontium Chloride Phytoplankton net taxonomy Irritant 2 Sampling gear deployment 2.1 Deployment Below is an overview of suggested hauling speeds for the different nets as well as the depth sampled, sample type, and at which stations samples will be taken. Below is an overview of the depth sampled, sample type and at which stations samples will be taken by net type. Gear Depth sampled Sample type St1 St2 St3 St4 St5 St6 Bottom depth 600 m 600 m 600 m 600 m 600 m 600 m Multinet 180 um Bott-0 m Mesozoopl. taxonomy 1 1 1 1 1 1 WP2/Multinet 180 um Bott-0 m Mesozoopl. stable isotope 1 1 1 1 1 1 Macrozoopl. net/ trawl Acoustic layer Macrozoopl. taxonomy 1 1 1 1 1 1 Macrozoopl. net/ trawl Acoustic layer Macrozoopl. stable isotope 1 1 1 1 1 1 WP2 net (from sea ice) 50-0 m Mesozoopl. taxonomy Phytoplankton net haul 50 – 0 m Phytoplankton taxonomy 1 1 1 1 1 1 Phytoplankton hand net haul (from sea ice) 20 – 0 m Phytoplankton taxonomy Total time net (hrs) 4 4 4 4 4 4 • ** Note that these are deployment procedures per what is used by NPI and IMR on R/V Kronprins Haakon. Deployment procedures and sampling plans should be updated to follow the cruise plan and the standard operating procedures for R/V Polarstern. Additionally, the nets used can be updated to reflect what is available on the R/V Polarstern. 2.1.1 Deployment of the multi net • Check that the small pin the rotating cylinder is in the correct position, pointing strait up towards the pin at the net. If not, see page 166 of the Nansen Legacy Sampling protocols (https://septentrio.uit.no/index.php/nansenlegacy/article/view/6684/6670). • Turn on the Multinet and make sure it is connected to and communicating with onboard computers. • Prepare the nets by using the bar to lift the springs into position. • Double check that the cod ends are placed in at the right net and make sure that the nets are not twisted before the multinet is lowered into the water. • More information can be found in “Multiplankton Operational Manual” from HydroBios. 2.1.2 Deployment of Macroplankton trawl /net Deployment procedure depends on what nets available. Preferably we would like to trawl or do a v-haul in the acoustic layer. 2.1.3 Deployment of the WP2 net 180 µm • When deploying a WP2 net from the ice the net will be deployed by hand using a rope that is marked at 50 m. • The rope should be secured to an ice screw or similar. • The net should be lowered and hauled with a steady speed. 2.1.4 Deployment of the phytoplankton net • Use a phytoplankton net with 20 µm mesh size attached to a metallic frame so that it can be attached to the winch aboard R/V Polarstern. • Double check that the cod end is attached and closed before deployment. • Lower the net to 50 m and haul upwards with a speed of 0.1 m s-1. • Rinse the net well with seawater and allow to drain until < 90 mL are left in the cod end. • Fill a measuring cylinder up to 90 mL by flushing the mesh side of the cod end with filtered seawater from a squeeze bottle. • Take sample into lab for fixation. 2.1.5 Deployment of the on-ice hand net sampling. • On the sea ice, make a large hole using an ice auger. Alternatively, use a hole made by the physics team for deployment of i.e., MSS, ROVs, etc. Ideally, the same hole can be used for net sampling and under-ice water sampling using a Rutner sampler. • Attach a small hand net with 20 µm mesh size to a rope of sufficient length and attach a 1-2 kg shackle below the cod end. • Make sure the valve of the cod is closed and slowly lower the net to 20 m. Slowly but smoothly haul by hand to the surface. Aim for 1meter each 3 seconds. • Wait until < 90 mL are left in the cod end, open the valve, and drain the sample in 100 mL measuring cylinder. Fill cylinder to 90 mL by flushing mesh in cod end with filtered seawater from a squeeze bottle. • Decant the cylinder contents into 100 mL brown glass bottle and bring to the lab for fixation. 2.2 Post-Deployment All nets should be freshwater rinsed after deployment. Samples should be treated as gently as possible throughout the process and taken to the wet lab for sorting and preservation immediately after collection. 2.3 Common Issues Identify frequent challenges encountered during sampling and provide effective solutions to address them. 3 Sample sorting-collection-preservation procedure 3.1 Mesozooplankton abundance/taxonomy • Samples for the analysis of mesozooplankton abundance and taxonomy will be sampled using a Multinet 180 µm. • Larger gelatinous zooplankton should be removed before preservation, by use of a spoon with holes, over a light table/ or white tray. • Filter the rest of the content of the sample through a 180 µm sieve placed over a white tray in case something gets spilled. • Move the sample into a 125 ml bottle, fill the bottle to the neck with seawater. • Add 10 mL Formaldehyde 37% (stabilized for histology free from acid). 3.2 Macrozooplankton abundance/taxonomy • Samples for the analysis of macrozooplankton abundance and taxonomy will be sampled using a macrozooplankton net or trawl. • Remove all gelatinous zooplankton (cnidarians, ctenophores) and fish, as well as other particularly large organisms, from the total sample. Place these removed organisms aside in the refrigerator or cold room (4°C). • Weigh the remaining sample after removing excess water by use of sieve (0.5 mm). • Mix the remaining sample gently to randomize the organisms. • Split the sample in 2 or 4 depending on the total volume. • Take out a subsample for taxonomy (the remaining sample can be used for stable isotope samples) • Weigh the sample (if a balance is available) • Preserve the sub-sample for taxonomy with a final 4% buffered formaldehyde solution in 250 or 500 mL bottles. To ensure the proper preservation of the organisms, their total volume should not exceed ca. ¼ of the bottle before adding seawater and fixative. • Picked-out taxa: Gelatinous zooplankton: Pick out all gelatinous zooplankton from the larger organisms that were previously removed from the total sample. Sort to lowest possible taxa, count total individuals, and take pictures using the lightboard including the scale bar. Sort out individuals (up to 10 ind of one species), measure length, weigh, take a picture, put in 20 mL vials or 40/60 mL bottles, add 96%EtOH, and store at -20 °C. • Picked-out taxa: Other zooplankton: Sort and identify all the organisms to the lowest possible taxonomic level, length-measure, weigh (one collective weight per taxa), and photograph them. Freeze the length-measured and/or weighed groups at -20 °C, each taxon in a separate plastic bag. 3.3 Mesozooplankton and mesozooplankton stable isotopes • Samples for mesozooplankton and macrozooplankton stable isotopes will be sampled from all deployed zooplankton nets. • Take out subsample and keep the rest of the sample in a cold room or fridge (+4C). • Sort out the main species either by using a lightboard (macrozooplankton) or under stereomicroscope (mesozooplankton) • Keep the sorted animals in sea water in petri dish or small beakers and keep the sample cold using ice or cold packs until there is enough individuals for ideally 3 replicates. • Add the needed number of individuals to a cryo vial • Store sample at -80°C (or -20°C if -80°C freezer isn’t available). 3.4 Phytoplankton hand net taxonomy • Decant sample into 100 mL brown glass bottle. • Under the fume hood, add 3 mL of strontiumchloride stock solution and allow to fix for about 5 minutes. • Then add 10 mL of 20% hexamine-buffered formaldehyde. • Store samples in +4°C refrigerator. Do not freeze! 3.5 On-ice hand net sampling • Decant sample into 100 mL brown glass bottle. • Under the fume hood, add 3 mL of strontiumchloride stock solution and allow to fix for about 5 minutes. • Then add 10 mL of 20% hexamine-buffered formaldehyde. • Store samples in +4°C refrigerator. Do not freeze! 4 Sample analysis method All plankton samples should be properly stored for shipment to the institute of Oceanology PAN (Sopot, Poland) for further analysis.