Increased sea ice cover alters food web structure in East Antarctica

Abstract

In recent years, sea ice cover along coasts of East Antarctica has tended to increase. To understand ecological implications of these environmental changes, we studied benthic food web structure on the coasts of Adélie Land during an event of unusually high sea ice cover (i.e. two successive austral summers without seasonal breakup). We used integrative trophic markers (stable isotope ratios of carbon, nitrogen and sulfur) to build ecological models and explored feeding habits of macroinvertebrates. In total, 28 taxa spanning most present animal groups and functional guilds were investigated. Our results indicate that the absence of seasonal sea ice breakup deeply influenced benthic food webs. Sympagic algae dominated the diet of many key consumers, and the trophic levels of invertebrates were low, suggesting omnivore consumers did not rely much on predation and/or scavenging. Our results provide insights about how Antarctic benthic consumers, which typically live in an extremely stable environment, might adapt their feeding habits in response to sudden changes in environmental conditions and trophic resource availability. They also show that local and/or global trends of sea ice increase in Antarctica have the potential to cause drastic changes in food web structure, and therefore to impact benthic communities.

Use of sea ice by arctic terns Sterna paradisaea in Antarctica and impacts of climate change

“…Although global warming is associated with decreases in arctic sea ice, there is regional variability in the Antarctic with reductions in the west but increasing sea ice cover in the Ross Sea and East Antarctica (Parkinson and Cavalieri ). Such changes could have major implications for food webs (Norkko et al , Michel et al ) and foraging conditions along the East Antarctic coastline. Polar regions are sensitive to climate change (Goosse et al ), but the complexity of geophysical processes in the Antarctic, particularly multidecadal‐scale contributions by deep‐water convection currents in the Southern Ocean (Zhang et al ) currently limits the ability to predict how the extent of Antarctic sea ice will be affected by anthropogenic climate change.…”

Abundance and Distributional Patterns of Benthic Peracarid Crustaceans From the Atlantic Sector of the Southern Ocean and Weddell Sea

“…Wlodarska-Kowalczuk et al (2004) showed, for example, that areas characterized by seasonal ice coverage had higher abundances of the benthic macrofauna compared to areas characterized by perennial ice coverage. Moreover, the lack of sea ice break-up events strongly alters the benthic food-web structure, causing a shift on the diet of the benthic organisms (Michel et al, 2019).…”

Seasonal Food Web Dynamics in the Antarctic Benthos of Tethys Bay (Ross Sea): Implications for Biodiversity Persistence Under Different Seasonal Sea-Ice Coverage

“…Specifically, sea-ice shrinking during spring, together with sea-ice break-up in summer, allows a massive increase in ice-bound primary production (sympagic production), which is subsequently released into the water column, fuelling both pelagic and benthic communities (Pusceddu et al, 1999;Lizotte, 2001;Leu et al, 2015). Under these conditions, sympagic algae represent the main direct (via vertical flux) and indirect (after sedimentation) food input for a large part of Antarctic marine diversity (Lizotte, 2001;Michel et al, 2019;Rossi et al, 2019).…”

“…The increased availability of basal resources after sea-ice break-up allows consumers to exploit a range of carbon sources in both the water column and on the bottom, reinforcing benthic-pelagic coupling (Cattaneo-Vietti et al, 1999;Kaehler et al, 2000;Dunton, 2001;Knox, 2006). The seasonal supply of sympagic algae thus becomes crucial to energy exchanges between ecosystem compartments, also affecting the structure and stability of communities (Hobson et al, 1995;Søreide et al, 2010;Leu et al, 2015;McMeans et al, 2015;Michel et al, 2019).…”

“…Recently, application of stable isotope analysis to Antarctic benthic communities has proved useful for describing space-time variations in nutrient fluxes associated with sea-ice dynamics (Michel et al, 2019;Rossi et al, 2019). Studies in the Ross Sea have demonstrated that sympagic production is readily incorporated into benthic biomass following sea-ice break-up (Norkko et al, 2007;Calizza et al, 2018), supporting between 30 and 80% of benthic secondary production (Wing et al, 2018).…”