Oxygen level control on foraminiferal distribution in Effingham Inlet, Vancouver Island, British Columbia, Canada

Samples were analyzed from Effingham Inlet, southwestern Vancouver Island, British Columbia, to assess the oceanographic controls on benthic foraminif eral distribution. The resultant proxy data will be used to interpret cores collected throughout the basin, and assess the causes of periodic variatio n in fish populations over time. Seven foraminiferal assemblages were recognized with the primary controllin g factors being oxygen content, and proportion of organic matter in the sed iment. The estuarine Buliminella Assemblage characterizes well-oxygenated e nvironments with high levels of terrestrial plant matter. This assemblage d isappears when oxygen levels fall beneath suboxic levels of 40 muM/kg. The Buccella Assemblage, dominated in part by attached forms and islandiellids, is typical of well-oxygenated bank environments in the region. The Psammos phaera Assemblage is related to the lower salinity and variable conditions present in the shallow water where it occurs. The Stainforthia-Nonionella A ssemblage characterizes one well-oxygenated environment outside the inlet. The Stainforthia-Bolivinellina Assemblage is typical of suboxic/dysoxic con ditions (10-40 muM/kg) in the outer basin, The Stainforthia Assemblage is i dentified from dysoxic environments of deepest parts of the outer basin. A gradation between the Stainforthia-Bolivinellina Assemblage and the Stainfo rthia Assemblage is significant as a whole range of suboxic/dysoxic/anoxic conditions are detectable, potentially permitting recognition of even subtl e variations in paleoceanographic/atmospheric circulation. The Stainforthia -Buccella Assemblage was recovered from the least oxygenated area of Effing ham Inlet under fully anoxic (with H2S) conditions, and provides evidence t hat even the most isolated portions of Effingham Inlet are periodically oxy genated.