A survey of environmental physico-chemical parameters during a minor coral mass bleaching event in Tahiti in 1993

Abstract

Hermatypic corals along two continuous 25-m-long line transects on the northern and eastern coasts of the island of Tahiti (Arue, buter reef slope, and Hitia'a, fringing reef, respectively) were monitored during a minor episode of coral bleaching in April and May 1993. From early February to the end of May, the physico-chemical parameters of the sea water (temperature, salinity, dissolved oxygen, pH and total solar irradiance) were noted once a week, and solar UV-B radiation was recorded from 1100 to 1400 hours every day.

The results are consistent with a synergistic interaction between temperature and UV-B radiation, possibly associated with total solar irradiance. The interval of four weeks between peaks in solar UV-B radiation and seawater temperature may explain why the 1993 bleaching in Tahiti was minor. Different patterns of bleaching occurred in different species, and all corals recovered within four to six weeks. Hermatypic corals appear to have multiform reactions in response to environmental stresses.