Sea ice cover increase is changing the invertebrates’ feeding habits
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The atmosphere and oceans are getting warmer all around the world, and there is concern about the rapid melting of the Greenland ice cap. Meanwhile, in parts of East Antarctica, an unexpected phenomenon is taking place: sea ice cover tends to increase, and leads to changes in the trophic habits of the organisms living there. This is evidenced by a recent study conducted by researchers from the FOCUS Research Unit (Faculty of Science) and published in Scientific Reports (1).
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ntarctica is home to one of the most biodiverse marine faunas of our planet. The species that live there face extreme but stable environmental conditions, such as very low temperatures or intense seasonality. These conditions have probably persisted for most of the last million years, and may have been a determining factor in the history of Antarctic wildlife evolution. Environmental stability in Antarctica is now threatened by climate change, which has rapid and contrasting impacts on the Southern Ocean. While the Western Antarctic Peninsula is one of the fastest warming regions in the world, leading to a decrease in sea ice coverage, the latter paradoxically tends to increase in some parts of East Antarctica, such as Adelie Land. This trend, certainly linked with complex phenomena occurring in Antarctica, is leading to changes in the feeding behaviour of organisms such as sponges, bivalves, starfish, sea urchins and sea cucumbers.
Under the supervision of Gilles Lepoint (FNRS Research associate),Loïc Michel, BELSPO post-doctoral fellow at the Laboratory of Oceanology (FOCUS Research Unit/Faculty of Sciences) visited the Dumont - d'Urville research station of the Paul-Emile Victor French Polar Institute (IPEV) during the austral summer of 2014-2015. Usually, during the austral summer, the waters surrounding the station are sea ice-free, as a result of the break-up phenomenon. However, in some of the last few years (particularly in 2013-2014 and 2014-2015), this summer break-up did not occur, and a thick layer of pack ice (more than two metres at the time of sampling) remained present throughout the summer.
The data collected during this research visit clearly demonstrate that the absence of break-up has profound consequences on the functioning of the food web in the vicinity of the station. "In order to understand the ecological implications of environmental changes, we studied the structure of the benthic food web on the Adelie Land coasts during an exceptionally high sea ice cover event (i.e. two successive austral summers without seasonal break-up)," explains Loïc Michel, first author of the scientific paper published in Scientific Reports (1). We have carried out isotopic analyses* on elements of interest such as carbon, nitrogen and sulphur, in order to build ecological models and study the feeding habits of macroinvertebrates. "A total of 28 taxa covering most animal groups present in the region were studied. The results obtained by the researchers clearly indicate that the absence of seasonal break-up has had a profound impact on benthic food webs.
"The persistence of sea ice on one side of the Antarctic continent, and the importance of ice melting on the other," says Gilles Lepoint,"could lead to a phase shift in coastal marine ecosystems, requiring organisms to continually adapt to survive climate-induced changes occurring in the food web. It could also cause radical changes in the structure of the food web and have an impact on benthic communities. "Faced with such major environmental changes, these animals, whose migration capacities are limited, can only adapt or disappear.
Researchers believe that in the longer term, the ability of Antarctic invertebrates to change their feeding habits in response to environmental conditions could facilitate their adaptation to future environmental changes. However, the new conditions in which animals live may also be unfavourable to them, forcing them to feed on food that is not sufficient to meet their nutritional needs. To build on this research and better understand how taxa adapt to their new environmental constraints, it is now important to conduct integrative studies exploring the links between dietary changes, the health status of organisms, and changes in the populations of the species concerned. The question of how community resilience could help benthic ecosystems recover from such extreme events also remains open.
*The isotopic analyses were carried out at FOCUS’ EA-IRMS platform, unique in the Wallonia-Brussels Federation, financed by the FNRS and ULiège.
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The research conducted by ULiège scientists contributes to the VERSO and RECTO projects, funded by the Belgian Federal Science Policy (BELSPO) within the framework of the Brain-be calls and of which Gilles Lepoint and Bruno Frédérich (UR FOCUS) are co-sponsors for the Uliège. The recent BELGICA 121 campaign was also funded by these projects. Many samples to be analyzed to study the effect of global changes in Antarctica!
Scientific reference
Loïc N. Michel, Bruno Danis, Philippe Dubois, Marc Eleaume, Jérôme Fournier, Cyril Gallut, Philip Jane & Gilles Lepoint. Increased sea ice cover alters food web structure in East Antarctica. (2019) 9:8062 | https://doi.org/10.1038/s41598-019-44605-5