Unusually high sea ice cover influences resource use by benthic invertebrates in coastal Antarctica

• Main Authors: Michel, Loïc, Dubois, Philippe, Eleaume, Marc, Fournier, Jérôme, Gallut, Cyril, Jane, Philip, Lepoint, Gilles
• Other Authors: MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège, FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
• Format: Conference Object
• Language: English
• Published: 2017
• Subjects: antarctica; food web; stable isotopes; benthos; invertebrates; sea ice; climate change; SIAR; southern ocean; Life sciences; Zoology; Aquatic sciences & oceanology; Environmental sciences & ecology; Sciences du vivant; Zoologie; Sciences aquatiques & océanologie; Sciences de l’environnement & écologie; Antarc*; Antarctic; Antarctic Peninsula; Antarctica; East Antarctica; Sea ice; Southern Ocean
• Online Access: https://orbi.uliege.be/handle/2268/210019; https://orbi.uliege.be/bitstream/2268/210019/1/Michel_BASIS2017.pdf

Antarctica currently undergoes strong and contrasted impacts linked with climate change. While the West Antarctic Peninsula is one of the most rapidly warming regions in the world, resulting in sea ice cover decrease, the sea ice cover of East Antarctica unexpectedly tends to increase, possibly in relation with changes in atmospheric circulation. Changes in sea ice cover are likely to influence benthic food web structure through modifications of benthic-pelagic coupling, disruption of benthic production and/or modifications of benthic community structure (i.e. resource availability for benthic consumers). Here, we studied shallow (0-20 m) benthic food web structure on the coasts of Petrels Island (Adélie Land, East Antarctica) during an event of unusually high spatial and temporal (two successive austral summers without seasonal break-up) sea ice cover. Using stable isotope ratios of C and N and the SIAR mixing model, we examined importance of 4 organic matter sources (benthic macroalgae, benthic biofilm, sympagic algae, suspended particulate organic matter) for nutrition of dominant primary consumers and omnivores. 14 invertebrate taxa including sessile and mobile polychaetes, gastropods, bivalves, sea stars, sea urchins and sea cucumbers were studied. Our results indicate that most benthic invertebrates predominantly relied on sympagic algae. Despite its very high abundance, trophic role of benthic biofilm seemed limited. However, interpretation of data was complicated by the peculiar ecophysiological features of Antarctic invertebrates, whose very low metabolic rates could be associated to low isotopic turnover and long time to reach isotopic equilibrium with their food items. Resource use by consumers from Adélie Land markedly differed from literature data about invertebrate diet in coastal Antarctica, suggesting 1) important influence of increased sea ice cover on benthic food web structure and 2) high spatial and/or temporal variation in the feeding habits of studied organisms, likely linked with a high ...