Molluscs from a shallow-water whale-fall in the North Atlantic

We conducted a species-level study of molluscs associated with a 5 m long 17 carcass of a minke whale at a depth of 125 m in the Kosterfjord (North Sea, Sweden). The 18 whale fall community was quantitatively compared with the community commonly living in 19 the surrounding soft-bottom sediments. Five years after the deployment of the dead whale at 20 the sea floor, the sediments around the whale carcass were dominated by the bivalve Thyasira 21 sarsi (Philippi), which is known to contain endosymbiotic sulphur-oxidizing bacteria, whilst 22 the background sediments were dominated by another thyasirid, T. equalis (Verril & Bush), 23 less dependent on chemosynthesis for its nutrition. The Kosterfjord samples were further 24 compared at the species level with mollusc abundance data derived from the literature and 25 including samples from different marine settings of the west coast of Sweden (active methane 26 seep, fjords, coastal and open marine environments). The results show high similarity 27 between the Kosterfjord whale-fall community and the community developed in one of the 28 Swedish fjords (Gullmar Fjord) during hypoxic conditions. This study indicates that at 29 shallow-water whale falls, the sulphophilic stage of the ecological succession is characterized 30 by generalist chemosynthetic bivalves commonly living in organic-rich, sulphidic 31 environments. 32