RECENT FORAMINIFERA AT THE PLATFORM MARGIN, DOOLITTLE'S GROTTO AND DOUBLE CAVES DIVE SITES, SAN SALVADOR ISLAND, BAHAMAS

Platform margins have received relatively little research attention in actualistic studies of West Indies benthic foraminifera even though the upper portions are commonly within the depth range accessible to direct observation via SCUBA. The small, isolated carbonate platform at San Salvador Island provides ample opportunities for such research. Preliminary results are reported herein for two popular sport-diving sites at the southwest tip of the island near Sandy Point, where the platform margin is only 300-375m from shore.

Doolittle's Grotto is a high-energy site located to the west and slightly north of Sandy Point. Here the platform edge is a gradual slope from a depth of 9m to 43m with two, shore-parallel coral-reef ridges dissected by crevasses and tunnels. Sediment samples were taken at depths ranging from 12m to 43m. No vegetation was observed on the seafloor; Halimeda spp. and soft algae were removed from their coral substrates and bagged separately under water.

At Double Caves, off the southern shore, a wall extends from the platform top at a depth of 12.2m to over 45m with several small ledges. Crevasses and caves dissect the platform margin, acting as conduits for sediment transport from the shelf. Sediment samples include a coarse-sediment sample taken from a cavity in the wall at 25.6m and a shelf sample at 39.7m.

The seafloor sediment at both sites is largely in transit. A high proportion of individuals on ledges and slopes are tests of shallow-water taxa (e.g., Archaias angulatus), which are commonly highly altered taphonomically. However, indigenous taxa are recognizable, especially in protected areas, and include the formerly established indicator genera Amphistegina, Textularia, and Bigenerina. With an inhospitable seafloor, live individuals are primarily those cemented directly to hard substrates or attached to algae growing on the reefs. Live species on Halimeda are dominated by Planorbulina sp. Major hard-substrate taxa are Homotrema rubra and Nubecularia sp. In contrast to the above taxa, some species appear to be restricted to the platform margin. These include Liebusella sp., Dusenburyina sp., and Reophax bermudezi, which are better known from much deeper water, and what appears to be Haddonia sp., a taxon known from the Indo-Pacific province, but not previously reported from the West Indies.