IMIS

The Agassiz Trawl (AGT) apparatus used comprised of a 1cm mesh with a mouth width of 2m, and once on the seabed was trawled at 1 knot for 5–10 minutes at each site. The AGT targeted macro- and megafaunal sized animals 1cm and larger, though with some smaller animals additionally captured in the sediment retained in trawls. A ‘cold-chain’ live sorting pipeline was followed on board, as outlined in detail in Glover et al. (2016). In summary, AGT sub-samples were carefully washed on 300-micron sieves in cold filtered seawater (CFSW), and annelid specimens were picked from sieve residue, cleaned and maintained in CFSW, and relaxed in Magnesium Chloride solution prior to specimen photography. Specimens were imaged using Canon EOS600D cameras either with 100mm Macro lens or through a Leica MZ7.5 microscope with SLR camera mount. Specimens were preliminary identified on-board to family level, numbered and recorded into a database, and fixed in 80% non-denatured ethanol. Samples that could not be fully sorted on board due to time restrictions were fixed in bulk for later sorting. All specimens were returned to the Natural History Museum London (NHM) and were re-examined using a Leica M216 stereomicroscope, and key morphological characters were imaged using a fitted Canon EOS600D camera. Specimens were identified to the best possible taxonomic level using original literature, specimen keys, and comparison with type specimen material from NHM collections. Where named species identifications were not possible, specimens were described as a morphospecies where the voucher number of a representative specimen is used as an informal species name for all specimens deemed to be the same species as the representative individual, e.g. Polynoidae sp. NHM_228. Where named species identifications were uncertain, the open nomenclature ‘cf.’ was used as a precautionary approach along with a representative voucher number, e.g. Antarctinoe cf. ferox NHM_232. Where specimens were fragmented, only fragments that clearly bore heads were counted and included in abundance records, as standard practice. Morphological taxonomic identifications are preliminary and will be updated following molecular investigations of these specimens using DNA barcoding. Glover, G. A., Dahlgren, G. T., Wiklund, H., Mohrbeck, I., and Smith, R. C. (2016). An End-to-End DNA Taxonomy Methodology for Benthic Biodiversity Survey in the Clarion-Clipperton Zone, Central Pacific Abyss. J. mar. sci. eng. 4. doi:10.3390/jmse4010002