Using correlative and mechanistic niche models to assess the sensitivity of the Antarctic echinoid Sterechinus neumayeri to climate change

The Southern Ocean is undergoing rapid environmental changes that are likely to have a profound impact on marine life, as organisms are adapted to sub-zero temperatures and display specific adaptations to polar conditions. However, species ecological and physiological responses to environmental changes remain poorly understood at large spatial scale owing to sparse observation data. In this context, correlative ecological niche modeling (ENMc) can prove useful. This approach is based on the correlation between species occurrences and environmental parameters to predict the potential species occupied space. However, this approach suffers from a series of limitations amongst which extrapolation and poor transferability performances in space and time. Mechanistic ecological niche modeling (ENMm) is a process-based approach that describes species functional traits in a dynamic environmental context and can therefore represent a complementary tool to understand processes that shape species distribution in a changing environment. In this study, we used both ENMc and ENMm projections to model the distribution of the Antarctic echinoid Sterechinus neumayeri. Both models were projected according to present (2005–2012) and future IPCC scenarios RCP 4.5 and 8.5 for (2050–2099). ENMc and ENMm projections are congruent and predict suitable current conditions for the species on the Antarctic shelf, in the Ross Sea and Prydz Bay areas. Unsuitable conditions are predicted in the northern Kerguelen Plateau and South Campbell Plateau due to observed lower food availability and higher sea water temperatures compared to other areas. In contrast, the two models diverge under future RCP 4.5 and 8.5 scenarios. According to ENMm projections, the species would not be able to grow nor reach sexual maturity over the entire ocean, whereas the Antarctic shelf is still projected as suitable by the ENMc. This study highlights the complementarity and relevance of EMN approaches to model large scale distribution patterns and assess species sensitivity and potential response to future environmental conditions.publishedVersio

Feeding ecology of Southern Ocean seastars inferred from stable isotopes ratios

The Southern Ocean is currently subjected to strong and contrasted impacts of climate change. The Western Antarctic Peninsula is one of the most rapidly warming regions of the world, resulting in sea ice cover decreases. Increasing seawater temperature and sea ice cover reduction in Western Antarctic Peninsula and associated regions will likely impact food web functioning through temperature-related changes in consumer physiology, modifications of benthic community structure (e.g. expansion of exogenous species such as predatory crabs), modifications of benthic-pelagic coupling intensity or disruption of benthic production. Asteroids (Echinoderms) are an important group of southern benthos. This group also has a great trophic variability and is potentially more resistant than other organisms to temperature changes (Peck et al. 2008). Consequently, they will be likely impacted by modifications in food webs functioning rather by direct warming and investigating their trophic ecology is necessary to infer how climate change will impact them. In this context, the aim of this study is to use stable isotopes ratios of C, N and S to infer sea stars trophic ecology. 16 species of sea stars spanning 10 different families sampled in multiple and contrasted habitats across Subantarctic (South Georgia, South Sandwich Islands, Falkland Islands) and Antarctic (South Shetland Islands, South Orkney Islands, Western Antarctic Peninsula) locations. In total, tegument samples from 213 specimens was analysed. Diversity and plasticity of asteroid diet along Southern Ocean coasts were explored through isotopic niche parametrisation (e.g. niche width and overlap between species and/or populations; Jackson et al. 2011). The data will also be used in a larger scale research project on the trophic ecology of Antarctic sea stars. This project will notably compare trophic resources supporting asteroid communities in Western Antarctic Peninsula, where sea ice cover is decreasing, and in Terre Adélie, where sea ice cover is increasing (Parkinson & Cavalieri 2012). Ultimately, this project will help understanding which ecological processes determine how an animal group copes with environmental modifications linked to climate change

Antarctic marine biodiversity challenged by global change: the CAML/SCAR-MarBIN benchmark

There is now undisputed evidence that climate change and modifications of the Earth system occurs, at faster rates in the polar regions. Among the many consequences we will be facing, the loss of biodiversity is probably of highest concern. CAML and SCAR-MarBIN are striving to provide the baseline information needed to assess the potential impact of climate change on Antarctic marine biodiversity. Through strong science plans, efficient data management and an unprecedented collaborative research effort within the IPY framework, CAML and SCAR-MarBIN intend to provide to scientists, environmental managers and decision-makers a sound benchmark against which future changes can reliably be assessed. This paper gives a brief description of the project’s synergies

Editorial: Antarctic Biology: Scale Matters.

A founding principle of the Antarctic Treaty is that, in the interests of all humankind, Antarctica should continue to be used exclusively for peaceful purposes and should not become the scene or object of international discord. From many standpoints, Antarctica is considered as a sanctuary, and plays a pivotal role in the global system. From an ecological point of view, Antarctica and the surrounding Southern Ocean harbor exceptional levels of biodiversity. Its ecosystems are, however, facing rapid climatic and environmental changes, and the scientific community, embodied by the Scientific Committee on Antarctic Research (SCAR), have identified the urgent need to understand the potential responses of these ecosystems. Such questions are extremely complex, as biodiversity, here defined as “the variability among living organisms from all sources, including inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems” (Convention on Biological Diversity, 1992), can vary at many different spatio-temporal scales and levels of biological organization, from molecules to entire ecosystems

Challenges of deep-sea biodiversity assessments in the Southern Ocean

Despite recent progress in deep-sea biodiversity assessments in the Southern Ocean (SO), there remain gaps in our knowledge that hamper effi cient deep-sea monitoring in times of rapid climate change. These include geographical sampling bias, depth and size-dependent faunal gaps in biology, ecology, distribution, and phylogeography, and the evolution of SO species. The phenomena of species patchiness and rarity are still not well understood, possibly because of our limited understanding of physiological adaptations and thresholds. Even though some shallow water species have been investigated physiologically, community scale studies on the effects of multiple stressors related to ongoing environmental change, including temperature rise, ocean acidification, and shifts in deposition of phytoplankton, are completely unknown for deep-sea organisms. Thus, the establishment of long-term and coordinated monitoring programs, such as those rapidly growing under the umbrella of the Southern Ocean Observing System (SOOS) or the Deep Ocean Observing Strategy (DOOS), may represent unique tools for measuring the status and trends of deep-sea and SO ecosystem

Data distribution: Patterns and implications

info:eu-repo/semantics/publishe

High-resolution description of insular and fjordic benthic food webs along the West Antarctic Peninsula

The West Antarctic Peninsula (WAP) is one of the most rapidly warming region on Earth. In this context, it is crucial to improve our understanding of the consequences of future changes in the local biotic and abiotic environments on marine ecosystem functioning. Here, we focused on food web structure of shallow-water benthic communities. In February 2023, the TANGO1 expedition, using a sailboat, brought nine Belgian scientists to the WAP. To assess the importance of environmental changes on local food web dynamics, five benthic communities were investigated, focusing on macroalgae forests (n=2) and sedimentary soft bottoms (n=3). These stations were distributed between two contrasted environments, Dodman Island (Grandidier Channel, 66°S) & Blaiklock Island (Bigourdan Fjord, 67.5°S). These two locations differed markedly in terms of sea-ice cover, and in terms of general hydrography (small island exposed to the Grandidier Channel’s currents VS fjord system surrounded by active glaciers). At each station, basal food sources (i.e. sediment-associated POM, water-column POM, macroalgae, microphytobenthos) as well as benthic invertebrates (435 individuals, 64 morphospecies) were sampled quantitatively to assess their biomass, and for later stable isotope analysis. Using stable isotope ratios of carbon, nitrogen and sulphur, and Bayesian tools, we aim to formally represent the communities in isotopic space, and to compare their topologies along the environmental gradient studied. These representations will then be used to test whether differences in food web structure reflect general community characteristics, such as the higher biomass of organisms measured in macroalgae forests, which also display the greatest species diversity.14. Life below wate

Trophic ecology of Southern Ocean sea stars inferred from stable isotopes ratios of C and N

The Southern Ocean undergoes strong and contrasted impacts of climate change. Increasing seawater temperature and sea ice cover reduction in Western Antarctic Peninsula and associated regions will likely impact food web structure and function. Sea stars (Echinoderms: Asteroidea) are an important group of the Southern Ocean benthos. They typically have highly variable feeding habits and are potentially more resistant than other organisms to temperature changes. Consequently, they will likely be impacted by modifications of the food web rather than by direct warming. Investigating their trophic ecology is therefore necessary to infer how climate change will impact them. In this context, the aim of this study was to use stable isotopes ratios of C, N and S to infer sea stars trophic ecology. During austral summers 2006 and 2009, sea stars were sampled in Subantarctic and Antarctic locations, with most of the samples coming from South Shetland Islands and South Georgia. The isotopic niche (proxy of the trophic niche) associated to each sea star population was explored through SIBER (Stable Isotope Bayesian Ellipses in R) metrics. Stable isotope ratios of sea stars were clearly different between South Shetland Islands and South Georgia. Sea stars of South Shetland Islands had smaller isotopic niches than sea stars of South Georgia. The overlap between the isotopic niches of sea star species was also important in South Shetland Islands, while isotopic niches of South Georgia were well separated. Difference of niche width and overlap between the two regions may be the result of different environmental conditions. In South Shetland Islands, sea star species may exploit a common benthic community relying on organic matter released during sea ice summer melting. In contrast, South Georgia is an oligotrophic environment with no sea ice. As resources are more limited, a higher trophic segregation between sea stars may appear to limit competition. Ultimately, this project highlighted the importance of sea ice in the trophic ecology of Antarctic sea stars. Our results suggest that future reduction of sea ice extent in Western Antarctica may have deleterious effect on sea star populations

Food web structure in a rapidly changing coastal environment: the West Antarctic Peninsula

The West Antarctic Peninsula (WAP) is one of the most rapidly changing regions in the world, in great part due to anthropogenic climate change. Steep environmental gradients in water temperature, sea ice cover and glacier melting influence are observed, but much is left to document about significance of those shifts for biological communities and ecosystem processes. Here, we aimed to study how environmental changes impact trophic interactions and ecological habits of benthic communities along the WAP. During the Belgica 121 expedition, dominant benthic mega- and macrofauna, as well as primary producers, were sampled in multiple stations featuring contrasted environmental conditions around the Gerlache Strait. Stable isotope ratios of δ 13C, δ15N and δ34S were measured and combined in an isotope niche analysis (SIBER). Our results suggest that changes in environmental features, notably ice disturbance, could cause alteration of food sources availability and fluxes to benthic organisms. Isotopic compositions of abundant species were more variable in stations with stronger ice disturbance. Besides baseline variability, this could be linked with use of alternative resources (niche expansion) in stations influenced by glacier melting. Those results provide a first step towards understanding links between environmental change and ecological responses of benthic consumers along the WAP.RECTO: Refugia and Ecosystem Tolerance in the Southern Ocean (BR/154/A1/RECTO

Trophic plasticity in Antarctic echinoderms: an adaptive trait with implications at ecosystem wide scale?

editorial reviewedClimate change is expected to have many adverse biological effects in Antarctica, including perturbation of feeding habits and energy fluxes. Food availability and predator/prey interactions are considered major factors dictating survival of Antarctic fauna, and foraging strategies have been shown to drive population evolution in some taxa. Whenever facing environmental changes, all organisms are expected to have some intrinsic ability to adapt. At shorter than evolutionary timescales, ecological plasticity in general, and trophic plasticity (i.e. the ability to display different feeding habits according to variation in environmental conditions) in particular, could be important adaptive mechanisms. There is increasing evidence that many key Antarctic benthos members show a high degree of trophic plasticity. It could prove to be a beneficial trait, allowing those species to shift their diet and match the new environments they will face in the future. However, diet shifts may also have detrimental aspects, such as feeding on items whose quality or nature are not optimal for the consumers. Ultimately, trophic plasticity could have important consequences at wider biological organisation levels, as it could modulate secondary production by those taxa, as well as the way they interact with other taxa through trophic relationships. Assessing trophic plasticity in Antarctic zoobenthos is therefore a promising avenue to shed light on how environmental change can shape organisms’ roles in ecosystem functioning. In this talk, we will focus on how trophic tracers (stables isotope ratios of C, N and S) can help delineating feeding plasticity in selected echinoderm (sea star and sea urchin taxa) in both Antarctic and Subantarctic coastal marine ecosystems