DIVERSITY OF BENTHIC FORAMINIFERA ON THE SHELF AND SLOPE OF THE NE ATLANTIC: ANALYSIS OF DATASETS

The objective of this work was to review the distribution of benthic foraminiferal species at the western European continental margin from 43-58 degrees N, determine their diversity, and generate a standardized taxonomy based on 44 publications (1913-2010) and unpublished information. Qualitative and quantitative data based upon foraminiferal occurrences and species abundances were included together with supplementary sedimentological and hydrographical data. From the species inventory, as well as from differences in morphological, physical, and hydrographic conditions in the study area, we defined six regions. The investigation of 2902 stations revealed 1486 species, of which 26% are synonymous. Most of the species have a hyaline test and live free, on or in the sediment. We recorded 608 species whose distributions were confined only to one of the six regions. Quantitative faunal data showed a general diversity increase from shelf to slope and two mid-slope diversity maxima, one located on the Basque continental margin at 550-850-m water depth and the other west of Ireland at 700-1100 m. In addition, the number of living species on the shelf generally increased from N-S. The latitudinal vs. depth distribution of six dominant species showed an irregular, lobate distribution pattern for the shelf regions. These species displayed similar distribution patterns on the continental slope, despite different modes of life, and different food and substrate preferences. This suggests that they have the same ecohabitat throughout their depth range. The faunal distribution pattern revealed close relationships between the different regions despite their varying hydrologic regimes. A delineation of one or two regions based on faunal criteria has not been attempted to date. There were no major distinctions in diversity among the six regions of the NE Atlantic, but the whole area exhibits an interregional diversity (gamma-diversity of 16), similar in magnitude to that of the Gulf of Mexico, In some parts of the study area, gaps in data coverage and differences in foraminiferal taxonomy and hydrographic conditions prevented the calculation of diversity indices.