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

The photosynthetic and respiratory responses of two scleractinian coral species from Florida, Dichocoenia stokesii and Meandrina meandrites were examined in vitro under conditions of elevated turbidity for up to 3 weeks. Turbidity ranges of 7-9, 14-16 and 28-30 NTU were rested and 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 days in both the 14-16 and the 28-30 NTU ranges compared to controls. Mucus production was clearly evident in the higher turbidity ranges. Exposure 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 never less than the saturation value of either species, and no change in light quality was observed as a function of turbidity. Since no significant differences were observed in gross photosynthetic oxygen production among any of the treatment or control groups, the turbidity-related change observed in the P:R ratio appears due to increased respiration, rather than decreased photosynthesis. These results suggest that adherence to turbidity-related water quality standards as presently defined in Florida, may result in short term stress and long term decline in at lease some coral species.