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Report to Joseph Ebanks, Cayman Turtle Farm
Algae In The Fish Lagoon And Cayman Turtle Farm Effluent Receiving Area: Recommendations For Monitoring Of Water Quality Improvements
July 11 2008
Thomas J. Goreau, PhD President, Global Coral Reef Alliance
Effluents from the Grand Cayman Turtle Farm have released material high in total suspended solids (TSS), biochemical oxygen demand (BOD), bacteria, and nutrients (Nitrogen and Phosphorus) that have degraded water quality in the adjacent coastal zone for forty years. This has resulted in a visible plume of suspended white particulate organic mater and bacteria, and fertilized intensive growth of weedy algae that have smothered the shoreline, bottom, and coral reef habitat. The Turtle Farm is now taking the national lead in treating effluent water in order to improve water quality and restore coral reef and fisheries habitat, after decades in which the impacts were ignored. The planned installation of superior and low cost technologies to treat the effluents should result in dramatic decreases of TSS, BOD, harmful bacteria, and nutrients, so algae overgrowth of the coastal zone should die back, allowing recovery of the reef. The purpose of this report is to discuss the changes now underway and how they can best be documented.
Impacts of the Turtle Farm on the coastal waters were first documented by Dr. Michael Risk, who found large amounts of coliform bacteria, typical of faecal material, in the discharge along with an increase in red coral boring sponges Cliona delitrix, on the bottom, which filter bacteria from water polluted with organic matter (Rose, C.S. & Risk, M.J., 1985. Increase in Cliona delitrix infestation of Montastrea cavernosa heads on an organically polluted portion of the Grand Cayman fringing reef. Marine Ecology 6 (4), 345–363). In 2003, the Cayman Islands Department of the Environment asked the author of this report to look at the site, and videos were taken of the deep Ray Ban outlet reef below the discharge site and along the shallow coastal zone. A small part of that documentation was used in a brief documentary on tourism, water quality, and coral reef health.
These video transects clearly showed that the massive algae blooms were confined to the area receiving the effluents and areas just down-current of them.
In June 2008 the same area was revisited in connection with the Turtle Farm’s Water Quality Improvement Program, and the algae in the breeding ponds and the Fish Lagoon were documented by photographs. Half a dozen other sites along the reef across North Sound, up current of the Turtle Farm were examined for comparison.