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The aim of JR275 is driven by the objectives of EvolHist, a core project at BAS studying biodiversity, biogeography, phylogeography and evolution in marine Antarctic fauna. The southern Weddell Sea, especially the Filchner Trough and the area to its west belong to the least biologically sampled regions in the Antarctic because of sea-ice conditions and current benthic biogeographical analysis rely on data from two previous cruises. These had used megafaunal collecting gear only, while most of the Antarctic marine invertebrates are macrofauna. The main objective of the biological component of this cruise is to collect marine invertebrates from vertical transects along the shelf and slopes and within the Filchner Trough (Figure 2 – Weddell station map). We will assess the biodiversity at local and regional scales (comparable to JR 144/BIOPEARL I to the Scotia Sea and JR179/BIOPEARL II to the Amundsen Sea), investigate the phylogenetic relationships of selected marine invertebrate taxa and their biogeography in reference to the climatological, oceanographical and geological history and assess the habitat characteristics in the southern Weddell Sea using UW video. The results will be used to determine of the role of Antarctica and extreme environments in general in evolutionary innovation and generation of global biodiversity.
The EvolHist team will run vertical transect lines with trawled benthic gear (Agassiz trawl, video camera and CTD equipped epibenthic sledge, Rauschert dregde), box corer and a full ocean depth CTD at each depth. The depth we will sample at are from the shelf to the deep sea will be 500m, 1000m, 1500m, 2000m and potentially 3000m. At present we plan 2 vertical transects along the continental slope, east and west in the mouth of the Filchner Trough, 3 transects across the Filchner Trough from the mouth to the edge of the ice shelf and a set of repeat shelf stations for variability assessments in comparison with data collected during JR179 off Adelaide Island. Before the trawling can take place, a swath survey has to be carried out in collaboration with JR259 to select seafloor areas suitable for benthic trawling. The selection of sample sites in the Filcher Trough area will also depend on the results of JR244 as JR275 had be the biological component of this joint marine geology, geophysics and biology cruise and joint objectives were set for the glaciological history of this area.
On board the AGT samples will sorted to phylum and class level before fixation while the EBS samples will be initially fixed and then sorted. DNA extractions of selected taxa will be carried out on board.

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RRS James Clark Ross cruise JR259 took place from 7th February 2012 to 22nd March 2012. It was a BAS National Capability cruise for the Geological Long Term Monitoring and Survey (LTMS) Workpackage. It was joined with cruise JR275 (Evolutionary History Workpackage), specifically benthic biology, which belonged to the same BAS Science Programme (Environmental Change and Evolution). The main objectives of JR259 and JR275 were closely integrated. It was also joined with JR255B (retrieval of oceanographic gliders from the south Drake Passage and South Orkney area) a logistics visit to Halley and a logistic visit to Signy. A cruise track is shown in Figure 1. Five days were lost at the start of the cruise due to late arrival of the ship in the Falklands and engineering works. Small surveys and dredging in the West Scotia Ridge and Herdman Bank and the passage to the South Sandwich Islands were successful and completed in good time. Work in the South Sandwich arc was abandoned because of bad weather and shortage of time. Work in the Weddell Sea was mainly for cruise JR275, and consisted of benthic biology sampling on the Weddell Sea continental margin and continental slope using Agassiz trawls and an Epibenthic Sledge fitted with a camera. This sampling was very successful. During this time, JR259 provided swath bathymetry coverage of sites to be sampled by the biologists, and to provide data and assessments of suitability of sites. This combination was very effective at identifying good sites for the biology sampling. A swath bathymetry survey of the continental slope from the shelf brake to locally over 2000 m was completed for the eastern Weddell Sea, as far as ice conditions and time would allow. After personnel uplift from Halley, and transect of the Weddell Sea, retrieval of oceanographic gliders for JR255B was attempted. This was partially successful, in that one of three gliders deployed was retrieved. Two gliders were not retrieved because their GPS location systems failed. A short swath survey of the South Scotia ridge was carried out before transit to Signy.

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