Distribution and ecology of benthic foraminifera in the Norwegian-Greenland Sea

Abstract

Factor analysis of the benthic foraminifera from 36 trigger-weight core tops from the Norwegian-Greenland Sea reveals four overlapping biofacies: (1) from 600 m to 1200 m water depth dominated by Melonis barleeanum, Pullenia bulloides, and Islandiella norcrossi; (2) from 950 m to 1500 m dominated by Cassidulina teretis; (3) from 1250 m to 3200 m dominated by Cibicides wuellerstorfi with Oridorsalis tener of secondary importance; and (4) from 2900 m to 3500 m dominated by Oridorsalis tener. Diversity is low relative to other deep-sea foraminiferal faunas, with only 1–3 species dominating each sample. The uniform physical properties of Norwegian-Greenland Sea deep water makes it unlikely that water mass characteristics control this foraminiferal distribution. Measurements from three GEOSECS stations show that below water depths of 400 m in the Greenland Basin and 1300 m in the Norwegian Basin water temperatures change by less than 0.7°C, salinities by less than 0.03‰, and oxygen content by less than 21 μmol/kg (0.5 ml/l) both within and between stations. GEOSECS nutrient data show slight to moderate changes with depth; however, variation between stations is greater than that found at an individual station. Given the lack of geographic faunal variation, changes in nutrient concentration and sediment type can scarcely be responsible for the observed foraminiferal distributions. A combination of hydrostatic pressure and bottom water temperatures is proposed as a possible controlling agent for the distribution of these benthic foraminifera.