ABSTRACT

This research project examines the changes in relative abundance of phytoplankton in arsenic contaminated waters at the Ron Phibun district of Nakhon Si Thammarat Province during July 2004 to June 2005. The chosen locations were four dredge ponds (abandoned tin mines) at Ron Phibun and Hintok sub-districts and two in dug ponds for community use at Saothong and Khuankoey sub-districts. The dominant phytoplankton in all study locations were cyanobacteria except for one location in the Saothong sub-district. The results demonstrated that there were major seasonal variations in phytoplankton abundance and in dominant genera associated with all sampling locations, and these were particularly evident during the rainy period. In general, all sampling locations showed a decrease in total abundance during the rainy season, but changes to the dominant population at any one location were different from all the others.