Species richness and abundance of monogonont rotifers in relation to environmental factors in the UNESCO Sakaerat Biosphere Reserve, Thailand

The UNESCO Sakaerat Biosphere Reserve plays an important role in nature conservation and environmental protection. Previous focus on terrestrial habitats and neglect of aquatic ecosystems has resulted in an incomplete picture of biodiversity of the area. Based on the first investigation of planktonic diversity, rotifers were collected seasonally at five localities from September 2013 to May 2014 using a Schindler-Patalas plankton trap and a plankton net. Fifteen families, 25 genera and 71 species of rotifers were identified. The most diverse families were Lecanidae, Brachionidae, Lepadellidae, and Trichocercidae, accounting for 80% of the total species count. The maximum species richness was reported at the reservoir, with 57 species (80% of the total), while the minimum species richness (34) was observed at the ponds. The rainy season had the highest density, followed by winter and summer, with 149.15 N/l from an intermittent stream, and 95.43 and 50.68 N/l from a pond, respectively. Most of the sampling sites at the three seasonal occasions were dominated by a planktonic species Polyarthra vulgaris. The results indicate that the seasonal variation of the rotifer assemblage is related to the seasonal variation of physicochemical parameters.