Ecological Niche Modeling of Sympatric Krill Predators Around Marguerite Bay, Western Antarctic Peninsula

Ari S. Friedlaender, David W. Johnston, William R. Fraser, Jennifer M. Burns, Patrick N. Halpin, and Daniel P. Costa

Adélie penguins (Pygoscelis adeliae), crabeater seals (Lobodon carcinophagus), humpback (Megaptera novaeangliae) and minke whales (Balaenoptera bonaerensis) are found in the waters surrounding the Western Antarctic Peninsula. Each species relies primarily on Antarctic krill (Euphausia superba) and has physiological constraints and foraging behaviors that dictate their ecological niches. Understanding the degree of ecological overlap between sympatric krill predators is critical to understanding and predicting the impacts on climate-driven changes on the Antarctic marine ecosystem. To explore ecological relationships amongst sympatric krill predators, we developed ecological niche models (ENMs) using a maximum entropy modeling approach (Maxent) that allows for the integration of data collected by a variety of means (e.g. satellite-based locations and visual observations). We created spatially-explicit probability distributions for the four krill predators in fall 2001 and 2002 in conjunction with a suite of environmental variables. We find areas within Marguerite Bay with high krill predator occurrence rates, or biological hot spots. We find the modeled ecological niches for Adélie penguins and crabeater seals may be affected by their physiological needs to haul-out on substrate. Thus, their distributions may be less dictated by proximity to prey and moreso by physical features that over time provide adequate access to prety. Humpback and minke whales, being fully marine and having greater energetic demands, occupy ecological niches more directly proximate to prey. We also find evidence to suggest the amount of overlap between modeled niches is relatively low, even for species with similar energetic requirements. In a rapidly changing and variable environment, our modeling work shows little indication that krill predators maintain similar ecological niches across years around Marguerite Bay. Given the amount of variability in the marine environment around the Antarctic Peninsula and how this affects local abundance of prey, there may be consequences for krill predators with historically little niche overlap to increase the potential for interspecific competition for shared prey resources.

STATUS UPDATE:
11/01/10: Revision accepted; editor letter sent to corresponding author.