Population dynamics of Pygoscelis penguins (1980–2012) and penguin dropping records (1916–2001) on Ardley Island of West Antarctica, in response to ENSO

Abstract

El Nino-Southern Oscillation (ENSO) has affected penguins and their habitats in the western Antarctic Peninsula. We used both historical penguin population dynamics data (1980–2012) and sedimentary lipids in penguin droppings (1916–2001) on Ardley Island to examine the responses of the Antarctic ecosystem to ENSO (El Nino/La Nina) events. The results showed that during the last 30 years, climate, marine food chain changes, and human activity have significantly affected penguin population sizes on Ardley Island. The Chinstrap (Pygoscelis antarctica) and Adelie (P. adeliae) penguin populations showed a good correlation with ENSO events. The Chinstrap penguin population decreased significantly because it was more sensitive to increasing human disturbance (e.g., scientific activity and tourism) than Adelie and Gentoo (P. papua), particularly during the breeding season. Compositional features of n-alkanes in penguin dropping sediments revealed that organic matter came from lower terrestrial plants, bacteria and algae. C23 was the main n-alkane heavy hydrocarbon indicating mosses and lichens in the penguin’s diet. Variation in the ratio of nC23/nC17 was closely correlated with ENSO events. The bacteria intrusion index (ratio of (iC15:0 + aC15:0)/nC15:0 for fatty acids) reflected significant increases in microorganism activity during several periods in this area. Meanwhile, the CPIA value for fatty acids decreased because micro-organisms contributed light hydrocarbon fatty acids to penguin droppings. Our results showed that the fine structure and molecular indices of fatty acids and n-alkanes in penguin dropping sediments can be used to explain climate-driven microbial processes, and to reveal the important role that microbes and bacteria play in the relatively simple Antarctic ecosystem.