A PALEOECOLOGICAL STUDY OF BENTHIC FORAMINIFERA IN TROPICAL MARINE MACROPHYTE COMMUNITIES

Benthic foraminifera are applied in paleoecology to characterize biological and physical settings in marine paleohabitats. Widely distributed in tropical shallow marine areas, modern foraminifera inhabit surface sediments as well as plant and algae communities. Thus, it is highly relevant to test what controls the diversity of benthic and epiphytic foraminifera assemblages in different habitats and how precisely can epiphytic foraminifera be used as an indicator of distinctive vegetation in the fossil record. This study focuses on Grahams Harbour, a shallow marine shelf on the north side of San Salvador, one of the outermost islands of the Bahamian Archipelago in the tropical North Atlantic Ocean. This setting provides an opportunity to sample various marine habitats, affected by tidal currents, which enter the study area through a narrow opening between North Point and Cut Cay.

Surface and subsurface sediment samples (N=14) were collected along a 500m transect off North Point. Grain size analyses of the sediment, qualitative and quantitative analyses of marine plant-algae communities, and analyses of the benthic foraminiferal assemblage were conducted in order to characterize biological and sedimentological settings in different shallow-marine habitats. Life and death assemblages of benthic foraminifera (>125 µm fraction) and the total density and diversity of epiphytic foraminifera were collected from marine macrophytes within 0.25 m² quadrats.

Sedimentology is highly variable, as are the macrophyte communities found in different habitats. Foraminiferal abundance and diversity show distinctive patterns likely reflecting a combination of substrate characteristics, vegetation density and type, and local water energy conditions. Increased productivity of living foraminifera is observed in habitats with stronger surface currents and on hard grounds. Within a habitat, the epiphytic foraminiferan life assemblage shows little concordance with the respective death assemblage. However, the compostion and diversity of the infaunal foraminiferan death assemblage suggest a strong correlation with marine macrophytes.