Evaluation of the environmental impact of dredging on intertidal coral reefs at Ko Phuket, Thailand, using ecological and physiological parameters

In 1986–1987 an intertidal reef flat at Phuket, Thailand was subject to increased sedimentation from a 9 mo dredging operation. Reef corals showed as much as a 30% reduction in living coral cover 1 yr after the start of dredging. Species diversity (measured as the Shannon Weaver indices H′c and H′n) also showed a significant decline at this time. In particular the dominant coral species on the reef, Porites lutea, suffered considerable mortality as a result of increased sedimentation. After the event, the reef recovered rapidly with coral cover values and diversity indices restored to former levels ca 22 mo after dredging began. No significant change in the linear growth rate, skeletal density and calcification of P. lutea was detected by the methods adopted in this study. Our results indicate that caution should be adopted in the use of retrospective coral growth rate analysis to diagnose the demise of a reef.