The effect of primary productivity and seasonality on the distribution of deep-sea benthic foraminifera in the North Atlantic

Deep-sea benthic foraminifera from 43 Holocene core tops in the North Atlantic were studied to evaluate the influence of primary productivity and the seasonality of primary productivity on the distributional patterns of species, faunal assemblages, and microhabitat groups. Two faunal assemblages, Epistominella exigua-Alabaminella weddellensis assemblage and Globocassidulina subglobosa-Epistominella umbonifera assemblage, were found to correlate with seasonality of primary productivity. The E. exigua-A. weddellensis assemblage is found at high latitudes and positively correlates with seasonality, while the G. subglobosa-E umbonifera assemblage is generally found at low latitudes and has a negative correlation. Correlation analysis indicates that the relative abundance of one species alone (E exigua or A. weddellensis) is not a strong indicator of either primary productivity or seasonality. No significant relationships are found between benthic foraminiferal species, faunal assemblages, or microhabitat groups and bottom water properties, which suggests that the deep-sea fauna may not be used to reconstruct bottom water properties in this region. Based on microhabitat preferences of individual species, the fauna is categorized into epifaunal, infaunal, and phytodetrital groups and is compared with primary productivity of the overlying surface waters and seasonality. No significant relationship was found between the relative abundance of the infaunal group and primary productivity or its seasonality, and only a weak correlation was found between these variables and the epifaunal group (r(2) = 0.33; 0.46). However, the relative abundances of the phytodetrital group correlate relatively well with seasonal variability (r(2) = 0.63), reflecting the association of these species with phytodetritus in regions marked by high seasonal variation in organic carbon flux. These results indicate that the relative abundance of the phytodetrital group may be used to reconstruct seasonality of productivity in the North Atlantic. (c) 2005 Elsevier Ltd. All rights reserved.