Using Chemical Elements to the Study of Trophic and Spatial Ecology in Marine Mammals of the Southwestern Atlantic Ocean

The ecology of marine mammals has been largely benefited from the use of biogeochemical markers. In this chapter we compiled information about studies using these tracers, with the aim of highlighting their relevance to understand some aspects of the trophic and spatial ecology of cetaceans, pinnipeds and sirenians from southwestern Atlantic Ocean (SAO). Stable isotope analysis is currently the mostly applied technique for such studies and its use increased considerably in the last few years. It is based on the premise that stable isotope composition in the tissues of the consumers reflects the composition of their diet that is effectively assimilated. Depending on the element being analyzed, information about habitat use patterns, diet composition and trophic position of the organisms can be inferred. Trace element analysis is underexplored as ecological tracers for marine mammals. There is only one study that analyzed Ba/Ca ratios in teeth of marine and freshwater dolphins to describe their patterns of habitat use in Brazil. Despite the known limitations of these chemical tracers, their use have shed light into different aspects of marine mammals’ ecology that would be difficult or impossible to obtain with alternative approaches.