Penguins past and present: Trace elements, stable isotopes, and population dynamics in Antarctic and sub-Antarctic penguins and seals

Abstract

Antarctica and the sub-Antarctic are remote regions where the impacts from climate change and anthropogenic activities are increasingly apparent. Previous studies show that the Antarctic is warming and has been affected by anthropogenic contaminants. Marine predators such as penguins and seals are commonly used in these regions as sentinels of ecosystem health as predator tissues can be used as non-invasive proxies of diet, population trends, and contaminant exposure. This thesis includes two separate studies which investigate the influence of climate change and human activity on Antarctic and sub-Antarctic ecosystems. First, Adelie penguin (Pygoscelis adeliae) eggshell samples were collected from four distinct regions of the Antarctic peninsula and analyzed for 12 heavy metals. Results were compared by geographic location, human activity, and trophic level differences to delineate drivers of variation. The main significant factors were geographic location and foraging; the influence of human presence was not an apparent driver, except for Zn. The toxic heavy metals As and Al were present in all samples suggesting ecosystem wide contamination, but Cd and Pb were widely undetectable. These results provide a baseline for future study of heavy metal exposure in Antarctic penguins using eggshell. Second, sediment cores were collected from two distinct sites on South Georgia Island, a sub-Antarctic island home to two key marine predators, the King Penguin (Aptenodytes patagonicus) and Antarctic fur seal (Arctocephalus gazella). Populations dynamics of these species have been affected by human exploitation and warming climate over the past two centuries, but records are sporadic. The sediment cores were determined to represent a 150-170 year time series. Dated sections were analyzed for total carbon (TN%), total nitrogen (TN%), δ13C, δ15N, and enumeration of biological remains (seal hairs and penguin feathers). These proxies of penguin and seal abundance were correlated with known changes in King Penguin populations since the early 1900s. These results provide details regarding the timing of penguin and seal recovery from exploitation concurrent with recent glacial retreat. This study validates the use of sediment cores as proxies for historical penguin and seal abundance on sub-Antarctic islands, allowing better management of these populations as the region continues to experience environmental change.