DETERMINATION OF SEDIMENT PROVENANCE AND CONTAMINANT SOURCES IN THE GUANICA WATERSHED OF PUERTO RICO

Terrestrially-sourced sediment pollution has been shown to have adverse impacts on nearshore coral reefs. However remedial actions are dependent on tracing this sediment to individual sources within the adjacent watershed. The Guánica watershed of southwest Puerto Rico has been negatively impacted by sediment pollution, due to extensive anthropogenic modifications, including the Lajas Valley agricultural reserve. Furthermore, the outlet of the watershed is in close proximity to a nearshore coral reef ecosystem, which has experienced substantial degradation over the previous decades. The purpose of this study is to use sediment fingerprinting, a multi-parameter analytical technique, to identify both the sources and relative contribution of sediment to the Guánica watershed. Approximately 80 sediment grab samples were collected from different land use/land cover (LU/LC) types (stream and reservoir banks, agricultural fields, pasturelands, forested land, coffee farming areas, and urban storm drains and road deposits) that represent different sediment sources, while two downstream sediment cores, suspended sediment from a significant rain event, and an offshore sediment trap represent sediment sinks. Initial sediment analytical data, including the percent organic carbon, percent carbonate, and the chemical index of alteration values are used to distinguish these sources and sinks. Results from this study will ultimately contribute to the growing knowledge of contaminants affecting coral reefs and guide effective land-use management practices within the Guánica watershed.