Biological characteristics of the drifting bivalve Gaimardia trapesina in the Southern Ocean

Abstract

Drifting invertebrate species represent an important link for the dispersal of benthic marine species that colonise islands. Shifts in water masses (i.e. speed, direction., play a fundamental role in determining food availability for suspension feeders that often form the base of the trophic chain. This study investigates the population structure, diet and distribution of the kelp-associated, drifting bivalve Gaimardia trapesina around the Southern Ocean Prince Edward Islands (PEI.. Samples of G. trapesina and its potential food sources were collected in April 2015 and 2016 and analysed using stable isotope and fatty acid analyses. Size-structure and attachment strength of G. trapesinawere also tested. The PEI lie in the path of the west-east flowing Antarctic Circumpolar Current and the highest abundances and largest individuals of G. trapesina were found on the north-east sides (downstream. of both islands, while the species was not present from the upstream side of either island. Diet analyses and SIAR mixing model indicated that G. trapesina feeds on suspended particulate matter, predominantly comprising a mixture of micro, nano and picoplankton. Long-term temporal variability was seen in ?13C signatures of G. trapesina when these were compared to samples collected in the 1990s and this variability is aligned with a southward shift of the Sub Antarctic Front. Here, we highlight the functional role of G. trapesina at the PEI and the implications of climate change effects on the biology of this species and the related marine community. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.