Distribution of rose bengal stained deep-sea benthic foraminifera from the Nova Scotian continental margin and Gulf of Maine

Abstract

Analysis of Rose Bengal stained benthic foraminifera in six boxcores taken from the Nova Scotian margin and Gulf of Maine reveals that foraminifera are vertically stratified within surficial sediments raised from 200 to 3000 m water depth. The consistent presence of infaunal taxa within the sediments demonstrates that these tolerant of a range of low-oxygen conditions as determined by pore-water manganese profiles. The habitat depth of foraminiferal populations, defined as the depth within which 95% of the fauna is found in a subcore, varies between the stations. A shallow habitat depth of 3 cm exists in shallow water (a 202 m core) in the Gulf of Maine. The habitat depth gradually increases on the continental slope with increasing water depth, reaching 11–13 cm in cores at 2225 and 3000 m, and then shoals to 4 cm in a core taken from 4800 m water depth. We suggest that the habitat pattern is related to the flux of organic carbon to the seafloor. At shallow depths, relatively high organic carbon flux results in a shallow oxic layer. The inferred oxic layer gradually increases on the continental slope and rise with increasing water depth, due to decreased organic carbon flux to the sediment-water interface. Carbon fluxes in the deep ocean are so low that pore waters are oxic and the organic carbon content is low, creating a food-limiting environment best suited to epifaunal taxa and reflected in a shallow habitat depth.