EFFECTS OF TURBIDITY ON THE PHOTOSYNTHESIS AND RESPIRATION OF 2 SOUTHFLORIDA REEF CORAL SPECIES

The photosynthetic and respiratory responses of two scleractinian cora l species from Florida, Dichocoenia stokesii and Meandrina meandrites were examined in vitro under conditions of elevated turbidity for up t o 3 weeks. Turbidity ranges of 7-9, 14-16 and 28-30 NTU were rested an d compared to controls at 0-2 NTU. The highest range corresponds with the maximum allowed during construction in Florida coastal waters. No differences were found between control and the 7-9 NTU groups. However , both species exhibited significant changes in P:R ratio after 2-3 da ys in both the 14-16 and the 28-30 NTU ranges compared to controls. Mu cus production was clearly evident in the higher turbidity ranges. Exp osure to 28-30 NTU depressed the P:R ratio to below 1.0, a level that was maintained for the 21-day duration of the experiments. Light was n ever less than the saturation value of either species, and no change i n light quality was observed as a function of turbidity. Since no sign ificant differences were observed in gross photosynthetic oxygen produ ction among any of the treatment or control groups, the turbidity-rela ted change observed in the P:R ratio appears due to increased respirat ion, rather than decreased photosynthesis. These results suggest that adherence to turbidity-related water quality standards as presently de fined in Florida, may result in short term stress and long term declin e in at lease some coral species.