Laboratory observations of rates and patterns of movement of continental margin benthic foraminifera

Abstract

Living calcareous and agglutinated benthic foraminifera were collected from a water depth of 220 m on the Charleston Bump east of Charleston, South Carolina and maintained in aquaria at ambient bottom water temperatures of 12 °C and 1 atm in the laboratory. The rates and patterns of movement of two species, Cibicidoides pachyderma (Rzehak, 1886) (a calcareous foraminifer) and Ammodiscus anguillae Höglund (1947) (an agglutinated foraminifer), are described and compared with published rates of movement for shallow- and deep-water taxa. Cibicidoides pachyderma and A. anguillae move laterally on a thin veneer of sediment in meandering patterns and both vertically and horizontally in thicker sediments with predominantly straighter patterns in the vertical plane. The recorded rates of movement at the substrate surface of C. pachyderma and A. anguillae vary from 1.0 to 23 and 1.0 to 20 mm/day, respectively. Within the sediment (~ 0.5 cm) A. anguillae moved with a rate varying between 1.0 and 10 mm/day. These rates are similar to rates for deep-sea foraminifera and to the slowest rates of shallow-water foraminifera. In the laboratory and in the absence of bioturbating organisms, both species moved in and out of sediments, suggesting that in nature they may be epifaunal and/or shallow infaunal taxa.