INVESTIGATING THE IMPACT OF WASTEWATER AND STORM WATER DISCHARGES ON COASTAL RECEIVING WATERS

Located on a coral atoll in the middle of the Pacific Ocean, the U.S. Army Kwajalein Atoll wanted to ensure that its operations did not cause any unreasonable degradation of the near pristine aquatic environment. To measure the cumulative impact of its wastewater and storm water discharges on the aquatic ecosystem, the Army initiated a bioassessment program – using the giant clam species, Tridacna maxima, as the indicator organism.Juvenile clams were deployed for a 3-month period in the vicinity of pollutant sources and reference sites. At the end of the exposure period, the clams were recovered and submitted for chemical analysis (metals, PAHs, pesticides, and PCBs). The analytical results showed that the giant clams were a successful bioindicator with clam tissue samples at monitoring sites near pollutant sources containing higher concentrations of chemicals than the reference sites. Because this measured contamination could not be correlated with wastewater and storm water discharges, a second clam study was conducted along with storm water and sediment sampling. The resulting analyses showed that the pollutants that were elevated in the clam tissue were also elevated in the sediment samples and present in the storm water runoff.