Mollusca collected by Agassiz trawl from the 2016 SO-AntEco (JR15005) expedition to the South Orkney Islands, Antarctica - data

<jats:p>This dataset contributes to the knowledge of macro- and megafaunal Mollusca associated with a range of benthic habitat types in the South Orkney Islands, Antarctica, an exceptionally diverse region of the Southern Ocean. The information presented is derived from Agassiz trawl samples collected on the archipelago’s shelf plateau and slope, within and outside of the South Orkney Islands Southern Shelf Marine Protected Area (SOISS MPA). Sampling was conducted in the framework of the British Antarctic Survey/SCAR “South Orkneys - State of the Antarctic Ecosystem” (SO-AntEco) project aboard RRS <jats:italic>James Clark Ross</jats:italic> during expedition JR15005 in Austral summer 2016. This dataset is published by the British Antarctic Survey under the licence CC-BY 4.0. We would appreciate it if you could follow the guidelines from the SCAR Data Policy (SCAR 2023) when using the data. If you have any questions regarding this dataset, do not hesitate to contact us via the contact information provided in the metadata or via data-biodiversity-aq@naturalsciences.be. Issues with the dataset can be reported at https://github.com/biodiversity-aq/data-publication/. This dataset is part of the Biodiversity, Evolution and Adaptation Project of the Environmental Change and Evolution Program of the British Antarctic Survey. The cruise report of the expedition is available at https://www.bodc.ac.uk/resources/inventories/cruise_inventory/reports/jr15005.pdf.</jats:p>           <jats:p>We report occurrences of Mollusca from individual samples taken with a 2 m-wide Agassiz trawl (AGT) in the framework of the February – March 2016 research expedition JR15005 of RRS <jats:italic>James Clark Ross</jats:italic> to the SOISS MPA and adjacent shelf and slope areas. Of 78 successful AGT deployments, 44 trawls at depths ranging from 235-2194 m yielded living Mollusca, totalling 2276 individuals, 67 morphospecies and 163 distributional records. One hundred and fifteen empty shells were also collected and recorded in the dataset. Three morphospecies (one Bivalvia and two Gastropoda) were sampled exclusively as empty shells, yielding a total of 70 morphospecies and 2391 specimens represented in the dataset. All specimens were preserved in 96% undenatured ethanol and are stored as vouchers in the collections of the British Antarctic Survey (BAS), Cambridge, United Kingdom. The publication of this dataset aims at increasing the knowledge on the biodiversity, abundance and geographical and bathymetric distribution of larger-sized epi- and shallow infaunal Mollusca of the South Orkney Islands.</jats:p>

section_content: The aim of the SO-AntEco expedition (JR15005) was to assess and contribute to a better understanding of the benthic biodiversity, community composition and zonation on the shelf and slope areas of the South Orkney Islands, including the SOISS MPA, and to provide information for future MPA monitoring and management. Previous studies have shown the archipelago to host an exceptionally high biodiversity for a polar site, most of which is contributed by marine benthic species (Barnes et al. 2009 ). To protect representative examples of marine ecosystems, habitats, and the biodiversity in the region, CCAMLR closed all demersal finfish fisheries around the islands in 1989 and established the SOISS MPA in 2009 (CCAMLR-XXVIII paragraph 7. 1; CM 91-03; CCAMLR (2009) ), the world's first MPA located entirely within the high seas (Brasier et al. 2018). Benthic sampling stations in the present dataset ranged from approximately 200 to 2000 m water depth and were chosen to cover different habitats, informed by the map of geomorphic zones by Dickens et al. (2014). These habitats included: (i) shelf, (ii) gentle shelf slope, and (iii) ridge along the southern shelf edge of the South Orkney Islands; and (i) shelf, (ii) steep shelf slope, (iii) marginal plateau, (iv) seamount, and (v) steep trough walls along the northern shelf edge (Brasier et al. 2018). 

We here report on the molluscs collected during the JR15005 campaign as they are a taxonomically and ecologically diverse phylum known to be a good surrogate taxon for entire benthic communities (Smith 2005, Tyler and Kowalewski 2017). With almost 700 formally described species in the Southern Ocean (Clarke and Johnston 2003), Mollusca is one of the more speciose higher-level taxa in the region. However, even though the group has been the target of investigations since the early Antarctic expeditions and, thus, is amongst the best known in the Southern Ocean (Clarke and Johnston 2003, De Broyer and Danis 2011), recent investigations in yet un(der)studied habitats, regions and depths have continued to record or describe new species on a regular basis (e. g., Aldea et al. (2009), Zamarro et al. (2013), Chen et al. (2015), Kantor et al. (2016) ). 

In this context, the publication of this dataset aims at increasing the knowledge on the macro-and megabenthic molluscs from the study area that encompasses the shelf edge and little investigated slope areas of the South Orkney Islands archipelago, Scotia Arc, in the Atlantic sector of the Southern Ocean.
section_name: Introduction

section_content: Title: Mollusca collected by Agassiz trawl from the 2016 SO-AntEco expedition to the South Orkney Islands, Antarctica -data Personnel: Jan Steger, Katrin Linse, Yi-Ming Gan, Huw J. Griffiths
section_name: Project description

section_content: The SO-AntEco -JR15005 expedition was part of the Biodiversity, Evolution and Adaptation Project of the Environmental Change and Evolution Program of the British Antarctic Survey (BAS). The publication of this dataset was funded by the Belgian Science Policy Office (BELSPO, contract n°FR/36/AN1/AntaBIS) in the framework of EU-LifeWatch as a contribution to the SCAR Antarctic Biodiversity Portal (biodiversity. aq).
section_name: Funding:

section_name: Sampling methods

section_content: The study area encompasses the continental shelf and slope of the South Orkney Islands, Scotia Arc, in the Atlantic sector of the Southern Ocean (Fig. 1A ). The archipelago is situated approximately 600 km north-east of the tip of the Antarctic Peninsula and hydrographically affected by the Antarctic Circumpolar Current in the north and the Weddell Sea Gyre in the south (Barnes et al. 2009, Meredith et al. 2011, Dickens et al. 2014). The present dataset provides species occurrences and specimen counts of larger-sized (mostly > 1 cm) Mollusca from 44 AGT hauls (= stations) taken during RRS James Clark Ross cruise JR15005 in 2016. Detailed station information is provided in Table 1, their geographic positions are plotted in Fig. 1B. Sampling description: Mollusca were collected using a 2 m-wide AGT with an outer 3 cm mesh-sized and an inner 1 cm mesh-sized net following a standardised deployment protocol (see JR15005 cruise report at https://www. bodc. ac. uk/resources/inventories/ cruise_inventory/report/16041/). Six major clusters of sampling stations were located to the south, west, northwest (subdivided into two sites: "North West" and "North West Trough"), north and northeast of the South Orkney Islands, as well as at Bruce Bank. Targeted sampling depths were 500, 750, 1000, 1500 and 2000 m. Furthermore, a single trawl was taken on the shelf off Signy Island at approximately 200 m depth. If conditions permitted, three replicate AGTs were taken at the shallower stations (500, 750 and 1000 m), while at least one haul was conducted at the deeper stations (1500 and 2000 m). Detailed locations of major clusters and individual sampling sites are shown in Fig. 1B. Swath multibeam bathymetry was used to assess seafloor topography prior to AGT deployments and -if possible (at < 1000 m water depth) -in situ seafloor imaging conducted at the same sites using the shallow underwater camera system (SUCS) to gather additional information on local faunal density, biomass and abundance (see also Brasier et al. (2018) ). 

Once on the bottom, the AGT was towed for 10 min at a speed of 1 kn. On deck, samples were sorted by hand into higher-level taxonomic groups (e. g., molluscan classes), the collected individuals roughly counted, placed in pre-cooled 96% ethanol and stored at -20°C. All molluscan specimens recovered during JR15005 were preserved. 

Treatment of samples: Identification of specimens was performed at BAS, based on external morphological characters using specialised literature (e. g., Dell (1990), Hain (1990 ), Numanami (1996), Steiner and Linse (2000), Aldea and Troncoso (2008), Engl (2012), Kantor et al. (2016) ) and an available reference collection. Mollusca were identified to the lowest possible taxonomic level, excluding one live collected individual and shell fragments too damaged for identification. Thirty-four percent of morphospecies (24 out of 70 species, Table 2 ) could only be classified at genus level or above: two of these were Solenogastres, two Polyplacophora, one Bivalvia and 19 Gastropoda. Taxa not identified to species level represent distinct morphospecies and do not belong to any other species in the dataset. Further morphological and genetic studies are required to clarify the status of these entities. Of morphospecies likely to represent undescribed species, DNA has been extracted for future COI sequence analysis. Three of the 70 morphospecies (Cuspidaria tenella E. A. Smith, 1907, Torellia sp. 1 [the sole representative of family Capulidae in our material] and Falsilunatia cf. scotiana) were collected only as empty shells. Quality control: All records were validated. Coordinates were plotted on a map to verify that the actual geographical location corresponds to its locality. Event dates and time were converted into ISO 8601 and verified with the field reports. All scientific names were checked for typos and matched to the species information backbone of the World Register of Marine Species (WoRMS Editorial Board (2018); http://marinespecies. org/); Life Science Identifiers (LSIDs) were assigned to each taxon as scientificNameID. 

Step description:

1. 

Benthic sampling with a 2 m-wide AGT in the South Orkney Islands during research cruise JR15005. 2. 

On board, the catch was hand-sorted into different higher-level taxa, with Mollusca segregated mostly to class level, and animals subsequently fixed in 96% ethanol at -20°C.
section_name: Description:

section_content: Taxonomic identification of the molluscan specimens was performed at the British Antarctic Survey (Cambridge, United Kingdom), based on morphological characters and with the aid of a stereomicroscope.
section_name: 3.

section_content: Species-level specimen counts were compiled for each trawl sample (Table 3 ). 5. 

Of species potentially new to science, DNA was extracted for future molecular analysis.
section_name: 4.

section_content: Description: Continental shelf and slope of the South Orkney Islands, Southern Ocean. 

Coordinates : -62. 4202 and -60. 2135 Latitude; -47. 1704 and -41. 0376 Longitude.
section_name: Geographic coverage

section_content: The present dataset provides information on the phylum Mollusca and includes five classes (Aplacophora, Polyplacophora, Bivalvia, Gastropoda and Scaphopoda). In total, 2276 living individuals were collected, representing 36 families, 67 species and 163 species-level distributional records (Table 3 ). To date, two morphospecies of the aplacophoran taxon Solenogastres, one morphospecies of an unidentified conoidean neogastropod and three morphospecies of nudibranchs (Gastropoda) have not been assigned to a family. Of live collected individuals, 1999 specimens (88%) were Bivalvia (accounting for 15 species), 158 (7%) Gastropoda (accounting for 45 species), 113 (5%) Scaphopoda (accounting for two species), four (0. 2%) Polyplacophora (accounting for three species) and two (0. 1%) Aplacophora (accounting for two species). Furthermore, 115 empty shells are recorded in the dataset. One family (Capulidae) and three species-level taxa (the cuspidariid bivalve Cuspidaria tenella E. A. Smith, 1907, the capulid gastropod Torellia sp. 1 and the naticid gastropod Falsilunatia cf. scotiana) were exclusively recorded as empty shells (Table 3 ).
section_name: Taxonomic coverage Description:

section_content: Data range: 2016-2-29 -2016-3-19.
section_name: Temporal coverage

section_content: Usage licence: Other IP rights notes: This work is licensed under a Creative Commons Attribution (CC-BY) 4. 0 Licence. scientificNameAuthorship The authorship information for the scientificName formatted according to the conventions of the applicable nomenclaturalCode.
section_name: Usage licence

section_name: Data resources

section_name: Acknowledgements

section_content: We show appreciation to the captain, crew and scientific team members of the RRS James Clark Ross expedition JR15005. We further would like to thank Robert Mesibov for his helpful feedback on our dataset and Cristian Aldea, an anonymous reviewer and the editor Anton P. van de Putte for their constructive comments.
section_name: Acknowledgements

section_content: Ross during expedition JR15005 in Austral summer 2016. This dataset is published by the British Antarctic Survey under the licence CC-BY 4. 0. We would appreciate it if you could follow the guidelines from the SCAR Data Policy (SCAR 2023) when using the data. If you have any questions regarding this dataset, do not hesitate to contact us via the contact information provided in the metadata or via data-biodiversityaq@naturalsciences. be. Issues with the dataset can be reported at https://github. com/ ‡ § | §

section_name: Species

section_content: JS identified and counted specimens, compiled the data, wrote and edited the manuscript. KL identified specimens, provided lab equipment and edited the manuscript. YMG compiled and prepared data for submission to GBIF and edited the manuscript. HG was PI of JR15005, provided the specimens, compiled and edited data and edited the manuscript.
section_name: Author contributions