Research Objectives:
A pervasive goal of biological oceanography is to understand the processes that structure pelagic communities. Research suggests that the distribution of oceanic species is influenced by physical and biological variability on a number of spatial-temporal scales. Our objective is to test the hypothesis that the dispersion and community of top predators vary in accordance with large-scale variability in physical structure and ocean productivity in pelagic ecosystems. We will therefore conduct a survey of bird and mammal use of distinct oceanographic domains in the southern Indian Ocean.
Two U.S. scientists will join French scientists on board a French research vessel near Reunion Island. The French scientists will sample the physical environment and estimate oceanic productivity, while the U.S. scientists will survey top predator distributions in physical and biological properties across a 35-degree latitudinal gradient from subtropical to subantarctic waters.
We hypothesize that top predator assemblages are structured by spatial gradients in hydrographic properties and ocean productivity patterns known to influence the distribution and patchiness of their prey (zooplankton, fish, and squid) and that the overall abundance of marine top predators within a specific oceanic domain is largely determined by ocean productivity. Also, we hypothesize that the energetic costs of foraging determine which types of top predators inhabit specific domains. Species with high foraging costs must exploit dense prey aggregations within highly productive areas. Conversely, taxa with low foraging costs can inhabit low-productivity areas with more dispersed prey.
We will quantify the association of specific water masses with top predator assemblages, as well as their aggregative response at hydrographic and bathymetric domains. Because top predators respond to oceanographic variability at multiple scales of time and space, we will use a variety of analytical methods to assess their responses in the context of large- and coarse-scale (thousands and tens of kilometers, respectively) hydrographic and ocean productivity patterns in the subtropical and subantarctic Indian Ocean. This interdisciplinary perspective will enhance our understanding of the way physical and biological processes structure pelagic communities in the southern Indian Ocean and will provide a model that has broader implications for the oceans as a whole.
