NE Atlantic benthic foraminifera: modern distribution patterns and palaeoecological significance

Abstract

Microfaunal evidence is presented from a region in the NE Atlantic Ocean characterized by well‐constrained and very uniform physiochemical water mass properties, but a significant gradient in surface ocean productivity. Notable changes in the species composition of benthic foraminiferal assemblages can be directly related to surface productivity and particulate organic matter supply to the deep ocean floor. Because of the labile nature of much organic matter as it reaches the sea floor, it is argued that benthic foraminifera, which exhibit a high preservation potential in most marine sediments, provide a better proxy for estimating past fluxes than bulk sediment organic carbon (OC) content. Three distinct assemblage groups are recognized: a Cassidulina laevigata group which is dominated by infaunal species and a relatively high sediment OC content; a Rhizammina spp. group which is also dominated by infaunal species; and an Epistominella exigua group dominated by epifaunal taxa and falling sediment OC content. Significant faunal assemblage changes appear to be independent of grain size.