The following dataset details the taxa of copepods present in a 378 m sediment trap located in the Northeast Scotia Sea, 52.80 degrees S, 40.14 degrees W, bottom depth 3748 m), as part of the Scotia Open Ocean Observatory programme (SCOOBIES, https://www.bas.ac.uk/project/scoobies/). The trap collected from late January to December 2018. With sampling periods ranging from 2 weeks to 1 month. Sediment traps are becoming a useful means of monitoring zooplankton throughout the year in remote locations. Funding: Clara Manno was supported by UK Research and Innovation Future Leaders Fellowships project CUPIDO (MR/T020962/1). Work was carried out as part of the Ecosystems programme at the British Antarctic Survey.

The quantities of key biologically active elements, carbon, nitrogen, and hydrogen, were measured from batches of eggs from the Antarctic Krill, Euphausia superba. These krill were collected in the "Western Core Box" krill time series region, an area to the north-west of South Georgia, on the RRS James Clark Ross research cruise JR17002 in the summer (January) 2018. Eggs were collected from ship board incubation experiments. Maternal parasite assemblage and load was determined using DNA metabarcoding. Krill with higher loads of apicomplexa and ciliate parasites laid eggs with lower quantities of carbon and nitrogen. These lower quality eggs may have lower survival and recruitment success, suggesting a mechanism by which parasites may influence krill population dynamics. Funding source: This research was supported by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 887760 (ParaKrill).

This dataset contains gridded spatial predictions of the distribution and density of Antarctic krill (Euphausia superba) in the South Scotia Sea, specifically within Subarea 48.2 of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). Both year-specific and decadal mean predictions are provided across years 2011-2020. All predictions were generated from a two-part hurdle model which used input data from (i) a spatially and temporally consistent acoustic krill survey around the South Orkney Islands and (ii) year-specific environmental covariates. The first hurdle model component was a binomial Generalized Additive Model (GAM) fitted to binary presence-absence krill data which predicts the probability of krill presence. The second component was a Gaussian GAM fitted to non-zero krill data which predicts krill density. Finally, these components were combined to identify where krill were both likely to be present and occur at high densities. Full model details are given in the associated publication. This dataset provides the spatial predictions generated from the binomial GAM, Gaussian GAM, and their combined product. Funding: PNT, SF and JJF were supported by the British Antarctic Survey's National Capability Antarctic Logistics and Infrastructure programme CONSEC, supported by the Natural Environment Research Council, a part of UK Research and Innovation.; VW-E and JJF were supported by the Pew Charitable Trusts under grant PA00034295. The South Orkney Islands acoustic trawl survey is part of the ongoing Norwegian Institute of Marine Research (IMR) project KRILL (p.no. 14246), which is supported by the Norwegian Research Council (NFR grant 222798), the Norwegian Ministry of Foreign Affairs, and IMR.

This dataset contains the object ID, morphotaxonomic name, and approximate size (in mm) of over 70,000 organisms identified from select Ocean Floor Observation and Bathymetry System (OFOBS) images from the cruise PS118 to the Weddell Sea from April - May 2019. Images were collected for assessing epibenthic megafauna communities and establishing temporal baselines for future studies. This work has been supported by Natural Environment Research Council (NERC) Independent Research Fellowship NE/S014756/1, awarded to EM. TK is funded by a Cambridge International and Newnham College Scholarship, administered by Cambridge Trust. RW and HG are funded by UK Research and Innovation (UKRI) Future Leaders Fellowship MR/ W01002X/1 "The past, present and future of unique cold-water benthic (seafloor) ecosystems in the Southern Ocean" awarded to RW. HG is also funded by BIOPOLE, funded by the NERC, under National Capability Science Multi-Centre award scheme (NC-SM2).

Benthic Macrofaunal abundance and biomass data collected during a series of ship-board sampling campaigns in the Barents Sea. As part of the NERC funded Changing Arctic Ocean programme, in July of 2017, 2018 and 2019, the RSS James Clark Ross followed a North-South transect at 30 degrees Longitude. In 2017 six stations were sampled (B3, B13, B14, B15, B16, B17); in 2018 seven stations were sampled (B3, B13, B14, Xs, B15, B16, B17); and in 2019 five stations were sampled (B3, B13, B14, B15, B16). Macrofaunal samples were collected using a USNL corer (surface area 0.1m<sup>2</sup>). On recovery all faunal samples were fixed and preserved with 10% buffered formaldehyde solution. The faunal samples were transported to Plymouth Marine Laboratory where the fauna were extracted, identified to species level where possible using the most up to date literature available, and biomassed (blotted wet weight) to species level. A reference collection has been created containing an example of each taxon to ensure maximum quality control was maintained by the three analysts that conducted the species identification and for subsequent cruise data generated. Funded by the NERC Changing Arctic Ocean Seafloor (ChAOS).

High-resolution X-ray computed tomography images of two deep-sea bamboo corals (Acanella arbuscula, Johnson, 1862; Keratoisis sp., Wright, 1869) collected from Baffin Bay and Davis Strait during a research expedition on board the CCGS Amundsen in July-August 2021. Corals were imaged using Micro-Focused X-Ray Computed Tomography at the Micro-Vis X-ray Imaging Centre (Southampton, UK) to non-destructively investigate their skeletal architecture, calcification strategies and growth patterns. Supported by a National Environmental Research Council Funded (INSPIRE) PhD [grant number NE/S007210/1, 2019-2027, awarded to T.J.W] and the National Research Facility for Lab X-ray CT (NXCT) [EPSRC grant number EP/T02593X/1].

This dataset set describes the developmental stages and the molecular barcoding of Terebellidae larvae identified from diver-collected samples on 2021-04-22 in Ryder Bay near Rothera Research Station, Antarctic Peninsula, Antarctica. Photographs were collected at seven stages across the larval development. Development was captured from the trochophore stage where the polychaete larvae were bound in mucus to the free swimming planktonic metatrochophore to the nectochaete stage. Molecular barcoding was performed using the 18S rRNA gene at the British Antarctic Survey. Funding: This study was funded by core funding to UKRI NERC-BAS.

In 2017, the RV METEOR M134 expedition investigated macrobenthic assemblages associated with methane seeps on the South Georgia continental shelf. Six shelf troughs with active methane seepage were sampled to assess species richness, abundance, and environmental conditions. Data were collected from eleven shelf stations, with species richness ranging from 19 to 51 species and abundances from 3,303 to 30,326 individuals per square meter. A total of 103 species were identified, with arthropods (primarily crustaceans) and annelids comprising most of the species richness. Environmental data include methane and sulfate flux, hydrogen sulfide concentrations, and sediment geochemistry. Seep assemblage data is combined with data from non-seep benthic communities from other expeditions.The dataset provides: 1) South Georgia methane seep station locations and environmental data. 2) Macrobenthic species absolute and normalized abundances at seep sites. 3) A combination of seep assemblages with non-seep benthic communities from other expeditions. Funding: The fieldwork for this study, was supported by the Deutsche Forschungsgemeinschaft (DFG) in the framework of the priority programme 'Antarctic Research with comparative investigations in Arctic ice areas' (project-id 40464014) and within the DFG-Research Center/Cluster of Excellence EXC 309 'The Ocean in the Earth System' (project-id 49926684). The expedition, titled 'Emissions of free gas around South Georgia: distribution, quantification, and sources for methane ebullition sites in sub-Antarctic waters,' was supported by MARUM - Center for Marine Environmental Sciences, Research Faculty University of Bremen, and the University of Bremen. Additional support came from the Helmholtz Association (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven). The cruise was funded by the German Research Foundation (DFG) and the Federal Ministry of Education and Research (BMBF). Katrin Linse is part of the British Antarctic Survey Polar Science for Planet Earth Programme (NC Science), funded by the Natural Environment Research Council (NERC). Studies around South Georgia were conducted under permit RAP 129/2016 (M134) issued by the Foreign & Commonwealth Office, UK. Macrobenthic faunal sorting was supported by the Natural Environment Research Council through a DEI Internship for Madeline PBC Anderson (via the NERC Diversity, Equity and Inclusion engagement funding) and an IAPETUS2 PhD studentship held by Madeline PBC Anderson (grant reference NE/S007431/1).

DNA sequencing data from octopus samples collected in the Southern Ocean. A small tissue sample was taken from the mantle of each octopus and placed immediately in 70 - 80 % ethanol for preservation, in preparation for DNA extraction.

Biological tissue samples from octopus species collected from the Southern Ocean, James Clark Ross cruise no. JR147/145. A large collection of tissue samples from deep sea and Antarctic target groups had already been collected in previous cruises. The specific objective of this cruise was to target three species of octopus, Pareledone charcoti (peak abundance 100m depth), Pareledone turqueti (peak abundance 100-200m) and Adelieledone polymorpha (peak abundance 250-350m), for the micro-evolution (i.e. population genetics) component of the project. Most of the octopuses were captured with an otter trawl, due to its relatively large sampling area and the fact that it can be trawled quickly (4 knots) which prevents octopuses from swimming out of it.