Habitat characteristics and carbonate cycling of macrophyte-supported polar carbonate factories (Svalbard) - Cruise No. MSM55 - June 11 - June 29, 2016 - Reykjavik (Iceland) - Longyearbyen (Norway) (English)

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Expedition 55 of RV MARIA S. MERIAN, referred to by the acronym ARCA, targeted on two contrasting sites of intense biogenic carbonate production in the coastal waters of the arctic Svalbard Archipelago. These are the rhodolith beds in Mosselbukta in the far North of the archipelagos main island Spitsbergen, and the extensive biogenic carbonate sediments accumulating in the strong hydrodynamic regime of the Spitsbergen- and Bjørnøy-Banken in the South. The habitat characteristics and biosedimentary dynamics of these cold-water carbonate factories was studies along bathymetrical gradients from the intertidal to aphotic depths, following a holistic approach. The scientific disciplines and methodological tool-kit comprised hydroacoustic habitat mapping (multibeam-echosounder and sidescan-sonar surveys), visual habitat mapping (research submersible and drop-camera surveys), hydrographic investigations including assessment of the aqueous carbonate system (CTD and water samples), epibenthos inventory (beam-trawls and excursions to shore), recording of short-term environmental fluctuations and benthic community dynamics (camera-lander), classical carbonate facies analysis of source and export areas (Shipek-grabs and excursions to shore), and an evaluation of carbonate (re)cycling, including budgeting calcification versus bioerosion (recovery of a 10-year settlement experiment). The vulnerability to past and future climate change, i.e. ocean acidification and warming, is studied by means of applying and developing geochemical proxies encoded in the skeletons of calcifiers (e.g., coralline algae, balanids, bivalves), and via on-board acidification and temperature-stress experiments with a key calcifier, the habitat forming coralline alga Lithothamnion glaciale.