Water Resources Research Act Program

Principal Investigators: Kynoch Reale-Munroe, Bernard Castillo, Carlos Ramos-Scharron

Abstract: Estuaries and bays surrounding the U.S. Virgin Islands (USVI) have been designated by local and federal agencies to encompass a myriad of services, such as, recreational uses, fishing, potable water sources and the sustainability of marine life. Unfortunately, the water quality in near-shore coastal habitats is deteriorating, in part due to non-point source pollution (NPS) resulting from land use changes and other anthropogenic activities. The U.S. Virgin Islands 2010 Impaired Waters List (EPA) shows that the most common causes of pollution throughout the US Virgin Islands (USVI) are sedimentation, effluent discharges, dissolved oxygen (DO) deficiencies and bacterial contamination. Total Maximum Daily Loads (TMDLs) for these pollutants are yet to be established for USVI waters. The main objectives of this study are to quantify the production of sediment and organic material, due to surface erosion on small watersheds within the East End Marine Park in St. Croix. Terrestrial monitoring sites have already been established throughout East End Bay and Boiler Bay watersheds by the installation of twenty-one sediment traps, which collect material produced from natural (i.e., vegetated hillslopes and naturally exposed cliff surfaces) and disturbed areas, represented by old unpaved roads that are currently used as foot trails. Material collected from all of the sediment traps will be analyzed for particulate organic material using the ‘Loss on Ignition’ method. In addition, rainfall and erosion will be correlated with turbidity, temperature, and DO in the receiving marine waters. Turbidity, DO, and conductivity data will be logged with automated equipment in the bays to describe how turbidity changes in response to rainfall and terrestrial runoff. Data collected will improve our understanding of erosion rates and the processes that control sediment and particulate organic material delivery into receiving marine ecosystems in small subtropical watersheds. The ability to provide a case study capable of illustrating the kinds of soil erosion processes that commonly occur here in the USVI and their effects on marine water quality, would be valuable to the development of TMDL limits for the various services expected from USVI waters.