Interactive effects of body size and environmental gradient on the trophic ecology of sea stars in an Antarctic fjord

• Published in: Marine Ecology Progress Series
• Main Authors: Le Bourg, B., Kuklinski, P., Balazy, P., Lepoint, Gilles, Michel, Loïc
• Other Authors: FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège, MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter-Research Science Publishing 2021
• Subjects: stable isotopes; trophic ecology; Southern ocean; sea star; starfish; trophic plasticity; SIBER; King George Island; Life sciences; Zoology; Aquatic sciences & oceanology; Environmental sciences & ecology; Sciences du vivant; Zoologie; Sciences aquatiques & océanologie; Sciences de l’environnement & écologie; Antarc*; Antarctic; South Shetland Islands; Southern Ocean
• Online Access: https://orbi.uliege.be/handle/2268/263544; https://doi.org/10.3354/meps13821

peer reviewed ABSTRACT: Antarctic sea stars can occupy different trophic niches and display different trophic levels, but, while the impacts of their body size and environmental features on their trophic niches are potentially important, they are presently understudied. Here we assessed the trophic ecology in relation to the size and habitat of sea stars in a fjord on King George Island (South Shetland Islands) using stable isotope values of carbon (δ 13 C), nitrogen (δ 15 N), and sulphur (δ 34 S). The disc radius influenced δ 13 C and δ 15 N values, whereas more limited changes in δ 13 C or δ 34 S values were related to arm length. Specifically, δ 13 C and δ 15 N values were linked to disc radius in generalist species ( Diplasterias brandti and Odontaster validus ), which could indicate ontogenetic diet shifts, while this relationship occurred less frequently in more specialised species ( Bathybiaster loripes , Notasterias bongraini , and Perknaster sladeni ). O. validus had a smaller isotopic niche size in the inner than the outer fjord. The niche overlap between D. brandti and O. validus was low in the inner fjord. Low resource availability within the fjord, linked to higher turbidity, could induce trophic niche constriction and interspecific resource segregation. This could represent a mechanism for competition avoidance in a resource-limited system. Conversely, higher resource availability could allow O. validus to expand and share its isotopic niche with D. brandti in the outer fjord with a limited risk of competition. This trophic plasticity will likely influence how O. validus copes with the present and future modification of environmental conditions induced by climate change. Refugia and Ecosystem Tolerance in the Southern Ocean