Comparing isotopic niche metrics of Antarctic seals between sites under distinct climate warming conditions

RENAN LIMA; JAVIER NEGRETE; JULIETA CEBUHAR; EDUARDO SECCHI; SILVINA BOTTA

Hobart

Conferencia; 9th SCAR OPEN SCIENCE CONFERENCE; 2020

Scientific Committee on Antarctic Research

The Southern Ocean has been particularly vulnerable to global climate change. While the western Antarctic Peninsula (WAP) has suffered significant temperature fluctuations, the eastern AP (EAP) has not yet showed evident signs of disturbance. Yet, little is known about the influence of warming on the ecology of mammals such as crabeater (Lobodon carcinophaga) (CS) and Weddell seals (Leptonychotes weddellii) (WS). We compared species sampled on EAP (Weddell Sea, 6 CS, 4 WS) and WAP (Danco Coast, 13 CS, 14 WS) between 2014-2016 using stable isotopes of whiskers to assess how environmental differences may be shaping habitat use and diet. Mean values were -21.7? (δ¹³C) and 7.0? (δ¹⁵N) for EAP CS; -23.0? (δ¹³C) and 6.7? (δ¹⁵N) for WAP CS; -16.4? (δ¹³C) and 14.5? (δ¹⁵N) for EAP WS, -21.6? (δ¹³C) and 12.7 ? (δ¹⁵N) for WAP WS. Niche metrics were estimated through Stable Isotope Bayesian Ellipses in R. EAP showed wider isotopic niches for both species (CS: 2.0 vs. 1.1?², WS: 7.8 vs. 1.4?²), which showed complete segregation within the isotopic space in both areas. δ¹³C and δ¹⁵N range were both larger for the EAP community (7.8-5.3? vs. 5.6-1.3?, respectively), as well as mean distance to centroid (4.7 vs. 2.9?) and mean nearest neighbor distance (9.5 vs. 5.8?). All results point to a higher trophic length and diversity of basal resources in the EAP, which can be attributed to a higher environmental stability. Isotopic niche differences between species and sites may be due to the influence of climate on baseline values.