Decline in skeletal growth of the coral Porites lutea from the Andaman Sea, South Thailand between 1984 and 2005

Of the few studies that have examined in situ coral growth responses to recent climate change, none have done so in equatorial waters subject to relatively high sea temperatures (annual mean[27C). This study compared the growth rate of Porites lutea from eight sites at Phuket, South Thailand between two time periods (December 1984–November 1986 and December 2003–November 2005). There was a significant decrease in coral calcification (23.5%) and linear extension rates (19.4–23.4%) between the two sampling periods at a number of sites, while skeletal bulk density remained unchanged. Over the last 46 years, sea temperatures (SST) in the area have risen at a rate of 0.161C per decade (current seasonal temperature range 28–30 C) and regression analysis of coral growth data is consistent with a link between rising temperature and reduced linear extension in the order of 46– 56% for every 1 C rise in SST. The apparent sensitivity of linear extension in P. lutea to increased SST suggests that corals in this part of the Andaman Sea may already be subjected to temperatures beyond their thermal optimum for skeletal growth.