Methodology:

Data were collected from each of 5 stations in 2017 (B13-B17) and 6 stations in 2018 (B13-B17 and Xs) during two consecutive cruises (RRS James Clark Ross: JR16006, 30th June to 8th August, 2017; JR17007: 10th July to 5th August, 2018) following a transect along the 30ºE meridian. At each station four replicate intact sediment cores (LWH: 20 x 20 x 12 cm) were obtained from replicate 0.1m2 USNL (Unites States Naval Laboratory) box cores using a core extruder, transferred to transparent acrylic aquaria (internal dimensions, LWH: 20 x 20 x 34 cm) and overlain with ~8 L (20cm depth) surface seawater (salinity, ~34). Aquaria (2017, n = 20; 2018, n = 24) were randomly transferred to one of two insulated fibreglass seawater baths (LWH: 1.2 x 1.2 x 0.8m, Tanks Direct, UK) and maintained at a representative ambient bottom temperature in the dark. At the end of incubation, the macrofauna retained (500 µm sieved) from each aquarium were fixed in 10% phosphate buffered formalin (4% formaldehyde) and stored in sealed plastic buckets for a minimum of three months. Prior to identification samples were rinsed and preserved in 70% industrial methylated spirit (IMS). Using a stereo microscope, all the animals were picked out of the residue, stored in vials containing 70% IMS, and identified to the lowest possible taxon with abundance and biomass per taxon noted. Biomass was obtained using blotted wet weight (± 0.0001g). The individual numbers of each taxa were counted to give abundance data. This was determined by the presence of a head in cases where specimens had been damaged. Any badly damaged specimens or parts of specimens where no head was present were separated into major group debris (annelid, mollusc and crustacea) pots and their presence noted as YES/NO for abundance). All molluscs were weighed inclusive of shells, tube dwelling polychaetes were weighed without tubes, and sediment was removed from the body cavity of specimens of Ctenodiscus crispatus prior to weighing.

Resolution:

A total of 2550 faunal individuals representing 153 taxa were recovered from stations B13-B17, with 1353 individuals (22.8602 g biomass) representing 123 taxa in 2017 and 1197 individuals (15.8390g biomass) representing 113 taxa in 2018. An additional 403 individuals (4.3943g biomass), representing 45 taxa, were recovered from station Xs in 2018. A total of 157 unique taxa (63% identified to species level, 92% to genus level; 2953 individuals, 43.0935g biomass), were recovered across all stations and both years.

All data are values per aquarium.

Data quality:

All data was input by 2 people and double checked at input. Biomass data was checked against the abundance data to ensure cells with values corresponded between the 2 files. Species names were checked against accepted names at http://www.marinespecies.org/. Faunal identification was independently quality assured by C. Louise McNeill and Tom Mesher (Plymouth Marine Laboratory).