Gray, S. C.
A comparative study of fringing reefs below developed v. undeveloped watersheds, U.S.Virgin Islands
Marine Science and Environmental Studies Department, University of San Diego
Type Period Note:
Final Report, 7/1/2008 - 12/31/2009
In the US Virgin Islands, sediment constitutes the largest pollutant of coastal waters by volume and is thought to be the primary cause of coral reef degradation. The factors governing the quantity, duration and type of sedimentat that may potentially affect a particular coral reef are complex and variable. Developing the most effective watershed sediment management strategies requires a thorough site-specific knowledge of the unique terrestrial, oceanographic and biological processes that impact the quantity, quality (type), and temporal variability of sedimentation on an individual reef. Therefore, detailed and comprehensive monitoring of both sedimentologic and physical processes affecting individual reefs is a critical compliment to ecological monitoring of coral reef health. The research objective of our study was to establish a baseline of data from which to evaluate how development in watersheds on St. John has impacted the quantity, quality (type), and spatial variability of sedimentation in bays with reefs. Empirical and modeling studies in these St. John watersheds have demonstrated that development (construction, area of impervious surfaces, dirt roads, etc.) has increased the sediment yields from the watersheds above background levels (Ramos-Scharron and Macdonald, 2005, 2007). Local environmental managers on St. John have been funded to implement sediment mitigation structures and need data to help locate and test their effectiveness and provide pre-mitigation baseline values. Approximately 56% of the area of the island of St. John, USVI is contained within the Virgin Islands National Park. Outside the boundaries of the park, the conversion of rural forests into home sites has enhanced sediment delivery into coastal waters by increasing erosion from roadbeds and cut slopes. Our approach was to collect and compare sediments within and among three bays with reefs - two drained by developed watersheds (Fish and Coral Bay) and one drained by a relatively pristine undeveloped watershed (Great Lameshur) within the VI National Park. We have focused our sampling to target a) locations with biologically monitored reefs, c) locations where watershed erosion processes have been well studied, and d) locations where future construction and/or sediment mitigation is planned or underway. This project was the first phase of an ongoing multi-year program of near-shore sediment monitoring that will compliment ongoing efforts by other researchers to monitor terrestrial watersheds and the marine biologic and physical environment. The data from the 2008-9 field season that was collected on this grant will comprise an important part of what will become a continuous 3+ year time series of sedimentation data for our sampling sites. We were funded by grants from NOAA General Coral Reef Conservation Program and NOAA ARRA to continue our sediment monitoring during the fall-winter seasons of 2009-2010. In partnership with educational and community groups we have been funded by the NOAA Coastal and Marine Habitat Restoration for funding under the American Recovery and Reinvestment Act (ARRA) to participate in a program of sediment erosion mitigation and monitoring in two of our study watersheds (Fish Bay and Coral Bay) called the "USVI Coastal Habitat Restoration through Watershed Stabilization" (http://www.usvircd.org/NOAAARRA_Grant.htm). The goal of this 2-year project is to reduce sediment loading to coral reef habitats by implementing erosion and sediment control BMPs. We will monitor sedimentation in Coral Bay at select locations through February of 2011. So by February of 2011, we will have monitored sedimentation/water quality for four field seasons in Fish and Lameshur Bays and two field seasons in Coral Bay (Aug.-Nov. 2007; Aug. 08-Mar. '09; Aug. 09-Mar.10; and Aug. 10-Feb. 11). The findings from this grant will provide critical baseline data for interpretation of future monitoring efforts. Our outreach goal was to establish ongoing research and educational partnerships between the University of San Diego, local environmental managers and community groups and researchers in the USVI.
FY2008 CRCP Project ID 1413; Project Title: General Coral Conservation Grants; Principal Investigator: Andy Bruckner. NOAA Grant: NA08NMF4630459