Sediment Stress, Water Turbidity and Sewage Impacts on Threatened Elkhorn Coral (Acropora palmata) Stands at Vega Baja, Puerto Rico.
AuthorsHernandez-Delgado, E., Y.M. Hutchinson-Delgado, R. Laureano, R. Hernández-Pacheco, T.M. Ruiz-Maldonado, J. Ohms, and P.L. Díaz Download PDF Open PDF in Browser
Poorly implemented beach renourishment activities and increasing raw sewage pollution from local storm sewers and other non-point sources have significantly impacted coral reef communities at the candidate Vega Baja Submarine Gardens Natural Reserve, Puerto Rico. There have been recurrent violations to legal water turbidity and microbiological water quality standards. Percent living cover of threatened Elkhorn coral (Acropora palmata) across six reefs declined by 29% within 1997 and 2008, for an annual mean loss of 2.65%. But mortality rocketed to 52% between December 2008 and June 2009 across the zone following beach renourishment and recurrent raw sewage spills. Mortality was lower at outer reefs with stronger oceanographic circulation (34-37%), in comparison to reefs located inside the shallow platform, closer to the shoreline (52-69%), or closer to polluted areas (81-97%). Massive coral mortality at Vega Baja produced a significant phase shift in community structure in many of the sites from dominance by A. palmata towards dominance by non-reef building benthic categories (i.e., algal turf, recently dead corals, and dead corals with algae). Recurrent sediment bedload from adjacent renourished beaches, as well as turbid and sewage-polluted runoff pulses, were devastating to Elkhorn coral stands. These violations to existing State and Federal regulations must be prevented in order to prevent further degradation of these highly vulnerable communities, as well as the continuous decline of its ecosystem resilience, functions and services. There is a need to designate the area as a Natural Reserve, and to develop and implement an integrated coastal-zone management plan with emphasis in protecting one of the largest remaining A. palmata stands in Puerto Rico and the northeastern Caribbean.