Benthic foraminiferal communities and microhabitat selection on the continental shelf off central Peru

Abstract

The ecology of the benthic foraminiferal community (62–150 and >150 μm) was studied in the continental shelf off Callao (12ºS) during April 2009. Five sediment stations were sampled along a cross-shelf transect. All the sites were subjected to dysoxic conditions in the bottom water, but differed in its sedimentary biogeochemical conditions. The inner-shelf, characterized by high contents of labile organic matter in the sediment surface and sulfidic conditions in the pore water, presented a community dominated by Bolivina costata, followed by Virgulinella fragilis, a spherical allogromiid morphotype, and Nonionella auris. The outer-shelf, more permanently subjected to the oxygen minimum zone, and characterized by sedimentary suboxic conditions and lower contents of labile organic matter, was inhabited by a community dominated by Bolivina humilis and Buliminella tenuata. Vertical distributions of V. fragilis, N. auris, and the spherical allogromiid morphotype likely reflect physiological and symbiotic adaptations to anoxia. We conclude that under this oxygen-deficient setting, the labile organic matter content and the sedimentary redox conditions govern the community parameters.