THE FORAMINIFERAN BACULOGYPSINA SPHAERULATA AS AN INDICATOR OF WATER QUALITY IN GUAM

Foraminifera are among the most common marine benthic organisms. Because of their abundance and the lengthy residence of their tests in marine sediment, researchers have long been interested in their applications for environmental monitoring. Foraminifera that harbor algal endosymbionts thrive in oligotrophic environments and are threatened by nutrient pollution, making them excellent proxies for changes in water quality. Push core analyses of back reef sediment indicate a decrease in the population density of Baculogypsina sphaerulata, the most abundant larger benthic and symbiont-bearing foraminiferan, in West Agaña Bay, Guam over the last several hundred years. This decline suggests a deterioration of the marine environment, likely due in part to elevated levels of anthropogenic nitrogen. Further, because larger benthic foraminifera are important producers of carbonate, this project is also concerned with quantifying changes in test thickness, which may reveal additional information regarding local environmental conditions. While preliminary carbonate results suggest no visible trend in test thickness with respect to time, a slight negative correlation was found between population density and test thickness in West Agaña Bay - a trend that has not been previously described in the literature. Because of biological similarities between symbiont-bearing foraminifera and hermatypic corals, threats to Baculogypsina sphaerulata may also reveal unfavorable environmental conditions for coral reefs.