Abstract

The main part of the Florida-Hatteras slope and adjacent shelf edge, between the latitudes of Cape Fear and Daytona Beach, is strongly affected by the movements of the Gulf Stream. The area is nutrient-rich and supports a large assemblage of benthic foraminifera, of which 165 species were found living in samples collected in 4 seasons of 1977. The only major biotope boundary, recognized on the basis of aspects of diversity, dominance, and assemblage composition, coincides approximately with the 100-m isobath; no promounced latitudinal changes can be identified. The shallower biotope (shelf edge and upper slope) is characterized by Shannon-Wiener diversity values (H̄) of >2 and dominance of Planulina exorna, the deeper biotope (middle and lower slopes) by H̄ of < 2 and dominance of Bolivina lowmani. The abundance of another common species, Cassidulina subglobosa, shows a conspicuous increase on part of the shelf edge and on the upper and middle slopes, down to a depth of about 300 m. An impoverished fauna, dominated by Anomalina semipunctata, may be associated with a deep-water coral bank. Cluster analysis does not indicate any significant shift of the major biotope boundary during the year. Anomalously high foraminiferal densities, with a mean value of >3000/3-ml, on a small part of the upper slope off Daytona Beach are related to the effects of periodic upwelling. The substrate here has a high clay-silt, organic carbon, and hydrocarbon content. Bolivina subaenariensis, a rare species elsewhere, is locally abundant and is a dominant species in the foraminiferal biota.

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