CESIMAR - CENPAT   25625
CENTRO PARA EL ESTUDIO DE SISTEMAS MARINOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Trophic ecology of fur seals and sea lions from northern Patagonia and their food webs through time
Autor/es:
CARDONA, L.; NEWSOME, S.D.; VALES, D.G. ; BORELLA ,FLORENCIA
Lugar:
Viña del Mar
Reunión:
Conferencia; 11th International Conference on the Applications of Stable Isotope Techniques to Ecological Studies; 2018
Institución organizadora:
Universidad Andrés Bello
Resumen:
High trophic level predators can integrate the biogeochemical characteristics of their habitat throughdiet, thus serving as ecosystem indicators. Here, we used carbon (δ13C) and nitrogen (δ15N) isotopeanalysis of bone collagen from ancient and modern South American fur seals (Arctocephalusaustralis) and sea lions (Otaria flavescens) as proxies of potential changes in a regional marine foodweb through time. Modern samples come from individuals stranded in northern Patagonia duringthe period 1990-2007, whereas ancient samples come from coastal archaeological sites fromsouthern Buenos Aires (~7000 14C YBP) and northern Patagonia (3500 + 800 14C YBP). Bulk bonecollagen isotope analysis shows that fur seals and sea lions displayed a steady resource partitioningthrough time with some overlap in δ13C vs δ15N space over the three periods under study. Inagreement with previous work, fur seals had lower δ13C and δ15N values in comparison with sea lions,indicating that fur seals largely forage on pelagic resources, whereas sea lions primarily consumebenthic prey. Mean δ13C and δ15N values of fur seals remained stable over time. In contrast, sea lionshad lower δ13C values ~7000 years ago than in subsequent periods, suggesting a more pelagic diet.Despite this shift, sea lions showed little overlap with the isotopic niche of Middle Holocene fur seals.Nevertheless, potential temporal shifts in the isotopic baseline of pelagic and coastal (benthic) foodwebs prevent us from robustly assessing changes in pinniped resource and habitat use. Currently,δ13C and δ15N analysis of individual amino acids (AAs) are in progress, and we anticipate this approachwill provide us with data on how baseline (essential AAs) δ13C and (source AAs) δ15N values havechanged over time in this ecosystem. In addition, offsets between source and trophic amino acid δ15Nvalues will provide a measure of pinniped trophic level and potential changes in food chain length inresponse to the development of industrial whaling, sealing, and fishing activities in this region overthe past three centuries.