Planktonic, benthic and sympagic copepods collected in the desalination unit during the XXXIVth Expedition of the Italian National Antarctic Program (PNRA)

Study Extent

This dataset describes the abundance and distribution of species of copepoda of the XXXIVth PNRA at Terra Nova Bay (Ross Sea, Antarctica) between 24 December 2018 to 02 February 2019.

Sampling

Samples were collected using the DU plant of MZS, whose intake pipe is located at 4 meters of depth in the locality of “Punta Stocchino” (Fig. 1). This plant is used to provide freshwater to the research base activities, operating during the entire expedition’s summer season, generally from mid-October, to the beginning of February. From the seawater intake pipe, a series of pipes and valves allow the water to flow to the main structure of the plant, located inside the research station, where the first steps of filtration (called “pre-filtration”) are conducted. These steps consist of a series of disposable filters positioned sequentially with decreasing mesh size. The first one is packed with anthracite, followed by polyester bag filters of 25 μm mesh size, and, finally, by polypropylene cartridges of 5 μm mesh size. The samples reported in this dataset were obtained from the biological material recovered by the 25 μm mesh size filters. More information on the technical specifications of the MZS DU plant can be found in (Cecchetto et al. 2021).

Quality Control

All records were validated. Coordinates were plotted on map to verify the actual geographical location. All scientific names were checked for typo and matched to the species information backbone of Worlds Register of Marine Species (http://marinespecies.org/) and LSID were assigned to each taxa as scientificNameID. Event dates are compliant to ISO 8601 standard.

Method steps

1. The 25 μm mesh size filters are frequently replaced by the DU plant’s technician as soon as the pressure inside the filter housing reaches warning levels to prevent the clogging of the system. After removing the filters from their respective housing, the same were transported to the laboratory, and processed following Cecchetto et al. 2021 and Cecchetto et al. 2022. Briefly, the filters, after removing the metal ring placed at the opening of the filter, were cut longitudinally in order to access its content, i.e. the biological material filtered. Using a scalpel with sterilized, disposable blades, different cuts were performed in different positions of the filter and stored at -20°C, obtaining pieces of the filter that would later be used for metagenomic research purposes. From the remaining parts of the filter, depending on the amount of biological material present on the filter’s surface, a volume of different 15ml falcon tubes of material were scooped from the filter’s surface, using a sterilized spatula, The falcon tubes were then brought to volume with 96% ethanol. The falcon tubes contained a mix of phytoplanktonic and zooplanktonic organisms in different ratios, depending on the biological community that was present in the water column facing the DU intake pipe during the filters’ operative time. The samples, stored at +4°C, were shipped to the MNA (Genoa section) laboratories, where the content of the falcon tubes was sorted and analyzed.
2. The collected copepods were counted and the taxonomic investigation, performed by Guido Bonello and Marco Grillo was performed to the lowest possible level and based upon historic and recent bibliography (Boxshall e Halsey 2004; Bonello et al. 2020). The online portal World Registry of Marine Species (WoRMS), Banyuls sur Mer marine Copepoda database (Razouls et al. 2022); https://copepodes.obs-banyuls.fr) was used to confirm acceptance of species names. When identification was inconclusive, only genus or family names were assigned. For the copepods recognized in this checklist, specimen selections were made to produce high-resolution images, useful for highlighting morphological characters for species classification. Various acquisition techniques were performed to obtain these photos. Scanning electron microscopy (SEM) and fluorescence microscopy employed different coloration with Congo Red and Fuchsin (Michels e Büntzow 2010; Ivanenko et al. 2012).
3. The original unsorted plankton matrix is stored in 96% ethanol, and also at -20°C. The copepod specimens, splitted, sorted and identified, are in 96% ethanol or fixed on a slide and permanently deposited in the biological collection of the MNA.
4. A metabarcoding methodology was also applied to the DU plant’s filters, and only some preliminary and qualitative results are reported here. Specifically, the relative abundance of 18S rRNA sequences identified by the taxonomic identification of the metabarcoding protocol as copepods in respect to the total amount of sequences (Fig. 3) are here reported only to illustrate the temporal dynamics that could be discerned by the metabarcoding approach during the sampling period.

Copepoda specimens were identified to lower possible taxonomic resolution.

1. Animalia
   rank: kingdom
2. Arthropoda
   rank: phylum
3. Copepoda
   rank: class
4. Calanoida
   rank: order
5. Cyclopoida
   rank: order
6. Harpacticoida
   rank: order
7. Metridinidae
   rank: family
8. Peltidiidae
   rank: family
9. Calanidae
   rank: family
10. Laophontidae
    rank: family
11. Dactylopusiidae
    rank: family
12. Hemicyclopinidae
    rank: family
13. Stephidae
    rank: family
14. Ancorabolidae
    rank: family
15. Oithonidae
    rank: family
16. Harpacticidae
    rank: family
17. Ameiridae
    rank: family
18. Tisbidae
    rank: family
19. Acartiidae
    rank: family

The desalination plant (-74.693 Latitude; 164.118 Longitude), connected to the Italian research base "Mario Zucchelli" (Terra Nova Bay, Ross Sea), is located at a depth of 4 m in the locality of "Punta Stocchino".