ALBERT

Description: Benthic foraminiferal faunas from the shelf and upper continental slope of the Celtic Sea (NE Atlantic) show a rich variety of Trochamminidae species. We recognized 31 taxa, of which 18 could be determined to species level. These 18 species comprise about 9% of all species of the family Trochamminidae that are described from Recent sediments worldwide. For species determination and generic classification, we used existing taxonomic concepts and assessed their applicability. Besides the morphology of the test and internal structures, different apertural features play a fundamental role in the systematic subdivision of the Trochamminidae. The position of the aperture controls the chamber arrangement and, therefore, the final shape of the test. However, we found no relationship between the apertural features and shape of the chambers as well as between apertural features and mode of life. Using apertural features for a sound taxonomic designation of our specimens proves difficult, because apertures are often obscured. Further, combined morphological and molecular-phylogenetic studies are required to constrain the taxonomic relevance of apertural characteristics.

Description: The objective of this work was to review the distribution of benthic foraminiferal species at the western European continental margin from 43–58°N, determine their diversity, and generate a standardized taxonomy based on 44 publications (1913–2010) and unpublished information.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 (-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.