Variations of phytoplankton in the lower part of the Tapee River Basin (TRB), Surat Thani Province, Thailand

บทคัดย่อ

This paper illustrates phytoplankton variations in the lower part of the Tapee River Basin (TRB), Surat Thani Province, Thailand, including species composition, relative abundance, diversity indices, patterns of distribution, and assessing aquatic ecosystem or water conditions, as well as considering potential measures for aquatic resources management effectively. Spatial and temporal sampling was designed to collect data at five study stations one time a season (two days a time) during three different seasons: dry, early rainy and heavy rainy seasons from December 2017 to August 2018. In each study station, the samples were collected by water sampler at three sides of rivers with three different water depths. Univariate and multivariate analyses were used to evaluate the data. The findings showed that a total of 63 phytoplankton genera belonging to eight Divisions were found. Three dominant genera were Actinastrum spp., Spirulina sp. and Aulacoseira sp. An average abundance was 1,917.8 units/L which has tended to increase from upstream to downstream. Average values of Pielou’s evenness index (J') and Shannon-Wiener’s diversity index (H') were 0.58 and 2.41, respectively, which could be classified as the medium diversity and distribution levels. Overall of Applied Algal Research Laboratory Phytoplankton Score (AARL - PP score) was 6.6, showing that water quality condition was generally meso-eutrophic and moderately-polluted. Based on the findings of this study, it was recommended that the properly aquatic resources management to maintain effectively ecosystems and fish stocks should be conducted. For example, monitoring program to regularly assess water quality should be done throughout the year, and restocking native herbivorous fish species would be the best conducted at station 5, and during the dry season.