BENTHIC FORAMINIFERAL DISTRIBUTION AND BIOMASS RELATED TO PORE-WATER OXYGEN-CONTENT - CENTRAL CALIFORNIA CONTINENTAL-SLOPE AND RISE

Benthic foraminiferal distributions and biomass were investigated with respect to bottom-water and pore-water dissolved oxygen concentrations and sedimentary organic carbon content at nine stations (624-3728 m) along two transects perpendicular to the central California coast. These stations were selected to intersect the oxygen minimum zone (OMZ) as it impinges on the seafloor. Foraminiferal numerical densities were determined at selected depths within the uppermost 9 cm of box cores, using either an adenosine triphosphate (ATP) assay or a Rose Bengal vital staining technique. Foraminiferal abundances from surficial sediments. as determined by the staining technique, varied considerably and were negatively correlated to bottom-water oxygen concentration. Maximal numerical densities occurred at a depth of 998 m, which is within the OMZ values ranged from 0 to 11.8 individuals cm-3 (determined by the ATP method) in surficial sediments. Six of nine cores exhibited subsurface maxima in foraminiferal abundance. and seven of the cores had Subsurface foraminiferal biomass maxima. Results indicate that certain species are infaunal while others only live in the surface sediment interval, an important observation for paleoceanographic studies utilizing stable isotopic analyses of deep-sea benthic foraminifera.