After the occurrence of the tsunami in 2004, the concentration of nutrients (silicate-silicon, ammoniumnitrogen
and orthophosphate-phosphorus) in the study areas increased due to tsunami run-up. chlorophyll a in the water gradually increased due to rapid growth of phytoplankton (red tide outbreak a few months after the tsunami). severe coral bleaching also occurred due to the increase in seawater temperatures to levels higher than the critical temperature. tresulted in a mass mortality of corals in shallow waters.