Abundance and diversity of phytoplankton and zooplankton in selected village tanks in Vavuniya, Sri Lanka

The abundance and diversity of planktons in selected village tanks namely Peraru, Nochchimoddai and Mamaduwa in the Vavuniya district were studied from March to April, 2021. The objectives of the study were to identify the phyto- and zooplanktons, and to estimate their abundance and diversity in the selected village tanks. Planktons were sampled weekly using a plankton net. Based on the morphological features, samples were initially identified up to the genus level using standard keys and their respective abundance was estimated using Sedgewick- rafter counting cell. Simultaneously, water samples were also collected at each location to determine the water quality parameters such as dissolved oxygen, electrical conductivity, pH, turbidity, temperature, and, nitrate and phosphate concentrations. The results showed that there were 16 genera of Chlorophyceae, six genera of Bacillariophyceae and seven genera of Cyanophyceae, while three species of Copepods, one species of Cladocerans and 10 species of Rotifers were identified. The dominant phytoplanktons belonged to Bacillariophyceae, and represented about 50% of total population of phytoplanktons while Cyanophyceae as the least abundant. Copepods were dominant in Peraru and Nochchimoddai tanks, representing more than 50% of the total zooplankton population while Rotifers were dominant in Mamaduwa village tank, with a 58% of total zooplankton population.