Abstract:
The objectives of this study are to determine the biodiversity of phytoplankton in Kwan Phayao and to study correlation between phytoplankton biodiversity and water quality in Kwan Phayao. As the result, it showed 7 Divisions, 38 Genera and 121 Species of phytoplankton. The most abundant species is Pediastrum simplex var. echinulatum Wittrock., showed the highest of Shannon-wiener s Index of 0.368. The multiple correlation between water quality, sampling station, species and quantity of phytoplankton in Kwan Phayao by MVSP software through CCA process. It found that Trachelomonas sp. 2, Trachelomonas sp. 3, Strombomonas sp.3, Cryptomonas sp. and Merismopedia sp. showed positive relation with total nitrogen, TKN, total ammonia and inorganic nitrogen. So, Gryrosigma sp., Trachelomonas sp.1 and Cylindrospermopsis sp. showed positive relation with nitrate. While Micractinium sp. and Pediastrum tetras (Ehrenberg) Ralfs showed positive relation with dissolved oxygen. The assessment of water quality using AARL-PP Score classified that Kwan Phayao was at a Mesotrophic level. While, AARL-PC score classified that Kwan Phayao was into Oligomesotrophic level. Thus, the Water Quality Index (WQI) classified into fair water quality as the third category of the surface water standard of Thailand. This study found that Pediastrum simple var. echinulatum Wittrock. could be a high nutrient bioindicator in Kwan Phayao.