Sustainability of reef ecosystem services under expanded water quality standards in St. Croix, USVI

Background/Question/Methods

Under the U.S. Clean Water Act, States and Territories are to establish water quality criteria to protect designated uses, such as fishable or swimmable water resources.  However, establishment of chemical and physical thresholds does not necessarily ensure protection of the biota, or long-term sustainability of ecosystem goods and services.  The U.S. Virgin Islands recently expanded their water quality standards to include biological criteria for coral reefs.  A decision support tool for evaluating sustainability of coral reefs and reef ecosystem services under alternative criteria levels can aid in establishing effective water quality criteria which reflect desired designated uses and long-term success.  As an initial step, we mapped reef condition and provisioning of reef ecosystem services around St. Croix.  Current reef condition was mapped by developing predictive models from EPA and NOAA point survey data, maps of benthic habitat, and bathymetry.  A suite of reef ecosystem services production functions, which translate reef condition into potential ecosystem services delivery, were derived from a literature review.  We investigated metrics for recreational opportunity, fisheries production, natural products potential, shoreline protection, and reef integrity.  Production functions were applied to map current ecosystem service delivery for St. Croix and compared across different water quality classes. 

Results/Conclusions

In general, different ecosystem services metrics (e.g. dive site quality, shoreline protection, fish production) were highly correlated with each other and indicators of reef integrity.  Across almost all ecosystem service metrics, Class A waters, designated for preservation of natural conditions, had higher levels than Class C waters.  This suggests that efforts to maintain threshold levels of biological condition can be quantitatively linked to higher production of ecosystem goods and services in these waters.  As such, an evaluation of ecosystem services provides one method for assessing whether water quality designations are achieving the desired results.  Long-term sustainability of ecosystem services is being evaluated by integrating models of watershed stressors (e.g. sediment, coastal development) with models of coral reef dynamics and provisioning of ecosystem services into the decision support tool, Envision.