ABSTRACT

Living benthonic foraminifers were collected from the South Texas outer continental shelf during the winter and spring of 1975, and the winter, spring, and fall of 1976. Stations were along four transects from about 20 kilometers offshore to the shelf break with the northernmost transect offshore from the entrance of Matagorda Bay and the southernmost transect offshore from the southern pass of Laguna Madre. Stations were also around East Flower Garden Bank, Stetson Bank, and the 28-Fathom Bank on the northern Gulf shelf. Samples from these stations were compared to samples taken around Hospital Rock and Southern Bank within the study area.

Samples were stained with Rose Bengal and species were identified and counted. Living benthonic foraminifers were also identified from plankton tows taken at the same stations as the benthonic samples. These data were evaluated to determine trends in the distribution, density, and diversity of the living species, and these trends then were compared to oceanographic processes to determine their usefulness as indicators of such processes.

Distribution of living benthonic foraminifers is influenced by depth and seasonality. Densities are generally highest nearshore and decrease toward the shelf break. Diversities are highest in mid-shelf and lowest in outer shelf areas. Nearshore populations are dominated by one or more species, notably Ammonia beccarii (Linne), Brizalina lowmani (Phleger and Parker), Nonionella basiloba (Cushman and McCulloch), Buliminella elegantissima (d'Orbigny), and Buliminiella cf. bassendorfensis (Cushman and Parker).

Brizalina lowmani was the most abundant living benthonic foraminifer of the South Texas outer continental shelf, both in the sediment and in the water column. The absence of dead forms in the water column, in addition to its abundance, suggests that this species has a meroplanktonic stage. Its distribution can be used to indicate bottom circulation, surface circulation, and eutrophism.