Live benthic foraminiferal faunas off Cape Blanc, NW-Africa: Community structure and microhabitats

Live (Rose-Bengal stained) benthic foraminifera were studied along a transe ct across the main area of organic matter deposition in the Cape Blanc upwe lling region. The faunal analyses suggest that at the shallowest station (1 200 m) the benthic ecosystem is permanently influenced by the upwelling, wh ereas at the deepest stations (3010 and 2530 m depth) the ocean bottom is s ubject to significant organic influxes only in summer. The vertical zonatio n of foraminiferal species in the sediment shows a close correspondence wit h the depth distribution of oxic respiration, nitrate and sulphate reductio n. It is suggested that this linkage is caused by the presence of various s tocks of anaerobic and sulphate- and nitrate-reducing bacteria; Deep infaun al foraminiferal species are thought to feed selectively, either on the bac terial stocks or on nutritious particles produced by bacterial degradation of more refractory organic matter. As such, foramininiferal microhabitats a re only indirectly controlled by pore water oxygen concentrations. (C) 1998 Elsevier Science Ltd. All rights reserved.