Research Product

Two six-week experiments were conducted to investigate the effects of drilling fluid on an experimental seagrass (Thalassia testudinum Konig et Sims) community. Microcosms consisted of 15.3 cm diameter seagrass cores maintained in the laboratory with flowing seawater. Effects on the community were measured by quantitative reduction of 10 numerically dominant macrofauna, and T. testudinum standing crop values. Also Ba and Cr levels were measured in animals, seagrass, and sediment. The results of both experiments indicate that a chronic exposure to 190 ppm Suspended Particulate Phase (SPP) of used drilling fluid will significantly reduce the numbers of individuals in several dominant species. There were no significant changes in Thalassia standing crop due to clay or drilling fluid exposure. Increases in Ba and Cr in macrofauna, seagrass shoots, and sediment were attributed to drilling fluid. There was a clear indication of bioaccumulation of Ba and Cr by benthic animals. The experiments described were successful in quantifying some of the effects of a chronic exposure to drilling fluid on a macrobenthic seagrass community.