The influence of Larsen-C ice-cover on macrobenthic peracarid crustacean assemblages on the Antarctic shelf

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On 12 July 2017, the Larsen-C Ice Shelf calved the largest iceberg (A68) originating from the Antarctic Peninsula ever recorded leaving 5,800 km² of seabed newly exposed to open-marine conditions which had very likely remained ice-covered for centuries or even since the last inter-glacial period. This enables us to address fundamental questions relating to the sustainability of polar continental shelves under climate change, the processes by which benthic populations migrate, and the degree to which the distribution of marine benthos can be used to interpret past responses to climate change. Biodiversity was not studied until 5 and 12 years respectively after the retreats of Larsen-A & B ice shelves. The Larsen-C Pearl project will now investigate the newly exposed shelf before significant colonisation begins from board of the RSS James Clarke Ross in February/March 2018. In 2019 this area will also be sampled from board of the RV Polarstern and it will be able for the first time in polar research to generate a baseline description of biodiversity, benthic community composition, species' turnover and colonisation, trophic structure at the very earliest opportunity underneath a former ice-covered area. This research will be key to producing predictions of the benthic systems’ response to future impacts on further ice-shelf collapse and improve fundamental understanding about the resilience of polar continental shelf ecosystems for a support of effective ecosystem management regulations.The project’s governing hypothesis is: "Until the calving of the Larsen-C iceberg, A68, the benthic fauna on the seabed beneath ice shelf has likely comprised oligotrophic assemblages resembling deep-sea Weddell Sea assemblages. The calving of A68, and the exposure of the seabed to open-marine and sea-ice conditions will initiate a rapid colonisation by new species that will transform the benthic ecosystem significantly within a short timeframe."Larsen-C Pearl will focus on peracarid crustaceans and follow four major objectives: 1. Biodiversity and assemblage structure assessment of the epi- and suprabenthic peracarid crustaceans; 2. Taxonomic descriptions of the selected peracarid species discovered in the Larsen-C area and reconstruction of their phylogeography; 3. Comparison of Larsen-C Year-1 biodiversity and peracarid assemblage structure (PS 118 expedition in 2019) with Year-0 and other areas (e.g. Filchner Trough and the ice free South Orkney Islands as well as deep sea of the Weddell Sea) to investigate turn-over, colonisation and/or succession; 4. Identification of peracarid functional groups beneath the Larsen-C ice shelf in year-0 and the next year after the calving and between ice-free areas.