FAU Institutional Repository http://purl.fcla.edu/fau/fauir This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute. Notice: © 2001 Environment Canada, Atlantic Region. This manuscript is an author version with the final publication available and may be cited as: Lapointe, B. E. (2001). Nutrient over-enrichment of South Florida’s coral reefs: how science and management failed to protect a national treasure. In T. Chopin & P. G. Wells (Eds.), Opportunities and challenges for protecting, restoring and enhancing coastal habitats in the Bay of Fundy: proceedings of the 4th Bay of Fundy Science Workshop (pp. 9-16). Dartmouth, Nova Scotia: Environment Canada, Atlantic Region. Opportunities and Challenges for Protecting, Restoring and Enhancing Coastal Habitats in the Bav ofFundy NUTRIENT OVER-ENRICHMENT OF SOUTH FLORIDA'S CORAL REEFS: HOW SCIENCE AND MANAGEMENT FAILED TO PROTECT A NATIONAL TREASURE B.E. Lapointe Marine Nutrient Dynamics, Division of Marine Sciences, Harbor Branch Oceanographic Institution, Inc., 5600 U.S. I North, Fl. Pierce, FL 34946, USA. [email protected] Introduction The Florida Keys are the most popular SCUBA diving and snorkeling destination in the world. The primary attraction is the 220-mile long Florida Reef Tract (FRT), the only living coral reef ecosystem within the continental United States, which attracts some 2.5 million tourists a year. Coral reefs are among the most productive and diverse ecosystems in the world and, as such, are comparable to their terrestrial counterparts-- tropical rainforests. Coral reefs grow as a thin veneer of living coral tissue on the outside of the hermatypic (reef-forming) skeleton and accrete massive limestone formations over geologic time. Coral reefs have evolved over hundreds of millions of years in tropical and subtropical waters that typically have very low concentrations of dissolved inorganic nutrients. Under such conditions, corals recycle limited nutrient supplies via a symbiosis in which the host coral releases waste dissolved nutrients that are tightly recycled by the symbiotic zooxanthellae algae-- which in tum provide carbon-rich compounds to the coral. The calcification process in corals also generates protons, which provide for co-transport of nutrients into the corals, providing these reef-builders with a competitive advantage over fleshy, non-calcareous algae under low nutrient conditions. Because ofthe ability of corals to thrive in nutrient-poor surface waters of tropical oceans, ecologists refer to them as "oases in ocean deserts". Scientists have long known that even slight increases in nutrient concentrations from sewage and other land-based human activities can have catastrophic effects on the health of coral reefs. Nutrient enrichment increases the growth and respiration rate of the nitrogen-limited symbiotic zooxanthellae, which decreases the photosynthesis to respiration ratio in corals and leads to physiological "stress". Nitrogen-enriched growth ofzooxanthellae also alters the biochemistryoflhe symbiosis by shifting algal photosynthesis towards production of protein at the expense of carbohydrate- undermining the functional nutrition of the symbiosis (ironically, the coral starves under high nitrogen conditions). Nutrient enrichment can also result in increased cover ofsoft corals (non-hennatypic), as well as blooms ofmacroalgae (> 2 em high) and endolithic filamentous algae, all of which outcompete and physically overgrow more slowly growing reef-forming hard corals. Elevated nutrients reduce overall reef growth by reducing calcification in corals, both directly and indirectly by reducing light and photosynthesis (which is directly linked to calcification) due to shading by macroalgae, turf algae, and increased light attenuation of the water column from increased phytoplankton biomass and turbidity. Nutrient enrichment also leads to increased 9 Opportunities and Challenges for Protecting, Restoring and Enhancing Coastal Habitats in the Bav ofFundy abundance ofherbivores and corallivores, including parrot fish, sea urchins, and "Crown-of-Thoms" starfish that can reduce living coral cover and accelerate bioerosion of limestone reef frameworks. ?,"·' Recognition of regional eutrophication in the Florida Keys Beginning in the late 1970's and early 1980's, hard coral cover began to decline with parallel increases in algal turf, macroalgae, and soft corals on patch and bank reefs of the FRT. This biotic phase-shift correlated with increasing human activities and associated nutrient loads from the Florida Keys that included deforestation, fertilizer use, sewage inputs, and fossil fuel combustion. In addition, a major change in water management policy in South Florida occurred in the late 1970's. This involved diverting massive flows ofstom1water runoff from the Everglades Agricultural Area (EAA) southward towards Everglades National Park (ENP) and Florida Bay, rather than backpumping into Lake Okeechobee that was causing hypereutrophication of the "Big Lake". Scientists documented the impacts ofthe increased nitrogen and phosphorus loads on eutrophication of the oligotrophic sawgrass and periphyton communities ofENP as commercial fishermen reported the expansion of macroalgae and phytoplankton blooms in seagrass meadows of Florida Bay. SCUBA divers on downstream reefs in the Florida Keys reported decreased visibility and the first coral bleaching of the FRT on reefs offshore Key West in summer of 1980. Heavy rains and high Everglades flows associated with the 1982-83 El Nino were followed by "white band" disease that caused widespread loss of elkhorn (Acropora palmata) and staghom (Acropora ce1Ticomis) corals while "black band" disease began eroding coral tissue on mountain (Montastrea spp.) and brain corals (Dip/aria, Colpophyllia). In summer of 1987, a massive die-off of turtle grass (Thalassia testudinum) began in central Florida Bay coincident with the first massive coral bleaching throughout theFKNMS. In response to the deteriorating water quality, loss of coral cover, and ecological problems in Florida Bay and the Florida Keys, over 50 scientists, educators, and managers attended a NOAA sponsored research and management workshop in Key Largo in June 1988. Rankings were made by the attendees as to the major threats and problems facing coral reefs of the Florida Keys. Although anchor damage by boaters had been considered the primary problem facing coral reefs in the 1970's, attendees now concluded that excessive nutrient loading and eutrophication was the top priority issue to be addressed to protect the coral reefs: "Excessive nutrients invading the Florida ReefTract from the Keys and Florida Bay are a serious and widespread problem" (NOAA 1988). A primary concern of attendees ofthat workshop was whetherornot their recommendations would be implemented and funded. Widespread attention to the declining status of South Florida's coral reefs occurred in 1990 when National Geographic featured the article "Florida's Imperiled Coral Reefs" that specifically noted the growing problem of nutrient pollution, algal blooms, and reef coral die-off. The international attention to the decline of coral reefs in South Florida helped to spur passage of the Florida Keys National Marine Sanctuary (FKNMS) and Protection Act on November 5, 1990, to "provide long-tem1 protection to the coral reef resources ofthe Florida Keys". Uniquely, the FKNMS Act included an inter-agency (USEPA, NOAA) Water Quality Protection Program 10 Opportunities and Challenges for Protecting, Restoring and Enhancing Coaswl Habitats in the Bav ofFundy (WQPP) intended to protect south Florida's coral reefs from further water quality degradation. The WQPP, which was implemented by USEP A, was intended to: 1) develop a monitoring program for water quality, coral reef communities, and seagrasses to determine "status and trends" and 2) recommend priority corrective actions and compliance schedules addressing point and non-point source pollution to restore and maintain the chemical, physical, and biological integrity of the FKNMS. During Phase I of the WQPP, information was compiled and synthesized on the status of water quality in the FKNMS and Florida Bay. Despite existing scientific knowledge of the role of nitrogen-rich runoff from the Everglades in fostering phytoplankton blooms, turbidity, and seagrass die-off in Florida Bay, the US EPA Phase I Report concluded: "even though the ultimate cause of the present seagrass die-offhas yet to be proven conclusively, it seems clear that anthropogenic nutrient input to the surface water is not responsible" (USEPA 1991). While USEPA's Phase I Report (1991) categorically dismissed the role of nutrient enrichment and eutrophication to the ecological problems of Florida Bay, the report alternatively promoted the hypothesis that the seagrass die-off resulted from "hypersalinity". The report claimed that draining of the Everglades caused the diversion of freshwater from Florida Bay, resulting in salinities of 55 ppt in central Florida Bay that were "fatal" to sea grasses. Actually, the high salinities in central Florida Bay referred to in the Phase I Report during the late I 980's were a result of a drought when South Florida received annual rainfall that was- 30-40% lower than nonnal several years in a row. Experimental studies decades earlier by McMillan and Moseley (1967) showed that T. tesllldinum, the seagrass that was dying off. could grow at salinities up to at least 60 ppt, higher than the salinity of 55 ppt which