Relationship between environmental conditions and recovery of the coral reefs in the Andaman coast of Thailand

Abstract

The coral reef ecosystem in the Andaman sea was studied by monitoring aquatic environmental conditions and reef condition from years 2005-2009. Following the Asian tsunami in December 2004, the ammonium-nitrogen concentration in the surface water in Ranong province ranged from 8.45-14.08 μ M, while in Phang Nga area, it was between 9.99 and 25.11 μ M. Mean sea surface temperatures in Ranong and Phang Nga were 30.6±0.4 °C during the dry season. The growth rate of Acropora spp. in Chong Khat bay, Surin Marine National Park, was 1.0 cm/month during the first 5 months after the tsunami. After this five-month period, corals, especially Acropora spp., showed signs of recovery but then faced extensive bleaching in May 2005. Three years after the tsunami, the coral reefs in deep water areas could grow and recover rapidly although they faced serious bleaching while coral reefs in the shallower waters were in a poor condition after serious bleaching in May 2005. This phenomenon revealed that the mass mortality of corals in shallow waters was enhanced by high seawater temperature and high turbidity due to phytoplankton blooms. Overall results indicate that the relationships between environmental conditions and coral reef status in the Andaman sea is an issue of great concern and coastal corals may gradually degrade in the near future unless action is taken to alleviate coastal environmental problems.