THE CHARACTERISTICS AND DISTRIBUTION OF ENCRUSTING FORAMINIFERA AT CAT ISLAND, BAHAMAS

Benthic foraminifera have long been recognized as crucial paleoenvironmental indicators. A peculiar subcategory of these foraminifera, encrusting foraminifera, live attached to structures on the ocean bed such as coral rubble and rocks. These have not received as much attention as have free foraminifera, despite their potential advantages. For example, encrusting foraminifera are fixed in place, making them difficult to transport out of habitat. However, interpretations of paleoenvironments derived from encrusting foraminifera require a firm understanding of how foraminiferal assemblages change with environmental factors in today’s seas. The goal of this study is to analyze the distribution of encrusting foraminifera at Cat Island, Bahamas, in order to compare these findings with previous research done on the surrounding islands in the Caribbean.

Cobble-sized pieces of coral rubble were sampled from eight locations that best represent the different reef environments from nearshore to deeper water. From each of these cobbles, 200 encrusting organisms were identified. Because of the disproportionate size of some of species, overall count was not necessarily representative of each species’ abundance. Therefore, the percent area taken up by each species on each cobble was compared as well by using ImageJ software to measure the area of each individual encruster. Both count and area data were analyzed using non-metric dimensional scaling in the R program. This enabled a clearer view of the relationship between factors such as water depth and the overall distribution of the foraminifera. A Spearman’s rank test was performed in order to test the significance of water depth.

Overall, Homotrema rubrum is dominant in nearshore reefs, whereas Gypsina plana dominates the offshore platform margins. In addition, the size, population density, and quality of preservation of the majority of foraminiferal species tend to decrease as water depth increases. Taking the statistical analyses into account, it seems clear that there is a significant monotonic relationship between the variation in foraminifera seen in the cobble samples and water depth. This evidence points to the distribution, size, population density, and preservation of encrusting foraminifera on cobble rubble being controlled primarily by water depth.