Composition and diversity patterns of deep sea benthic foraminifera from the Panama basin, eastern equatorial Pacific

Abstract

Environmental controls affecting the composition and distribution of deep sea benthic foraminifera were analyzed in the Panama Basin (Eastern Equatorial Pacific). For this study, results of the analysis of a new set of 33 core-top samples from the upper-lower slope (714–3819 mbsf) were integrated with previous data from this area.The composition of the foraminiferal assemblages resembles a typical deep sea association, illustrating a close relationship with dissolved oxygen at the seafloor and indirectly with surface productivity. Low oxygen content and organic matter influx, as inferred in the eastern Panama Basin, are connected to terrigenous supply and seasonal upwelling on the Panama Bight and southern Costa Rica. Buliminids, bolivinids, and Epistominella spp. are common elements of the continental slope. In addition, physiographic aspects such as the type of substrate, turbidity fluxes, and bottom currents also exert control over some of the described taxa and defined morphogroups. A broad exploration of the infaunal/epifaunal relationships in the basin does not suggest a clear relationship with dissolved oxygen content. However, there are fluctuations in the proportion of some of the defined epifaunal morphogroups and selected taxa (e.g. Cibicidoides wuellerstorfi, Chilostomella oolina, and Hoeglundina elegans, among others) along the Carnegie Ridge. These changes are explained by the variable physiographic features (surface upwelling, strong bottom currents) that coalesce in this part of the Panama Basin.Furthermore, re-evaluation of the foraminiferal morphogroups in two deep sea cores that comprised the last 25 ky, indicate that some taxa of the recent samples (Cassidulina spp. and Siphouvigerina peregrina, among others) reacted to paleoproductivity and bottom current fluctuations at the end of the Last Glacial Maximum and the Younger Dryas.Despite the lack of ecological data in the foraminiferal assemblages for a large proportion of the Panama Basin, the application of selected taxa or morphogroups as proxies for paleoceanographic conditions is promising.