Rotifer community structure in tropical lakes with different environmental characteristics related to ecosystem health

Aim: This study was conducted to evaluate the rotifer composition and abundance in lakes with different environmental characteristics in an attempt to identify the relationship between the rotifer community structure and environmental parameters. Methodology: Bimonthly samplings were carried out in Sembrong, Putrajaya and Subang lakes from April 2015 to February 2016. Duplicate rotifer samples were collected with a 60 pm mesh net using vertical hauls from about 30 cm from bottom to the surface, and preserved with 10% buffered formalin to produce 5% final solution for identification and enumeration. Physico-chemical parameters were measured in situ using YSI multi-parameter, and nutrient analyses were accomplished upon arrival in the laboratory of Marine Biotechnology, Universiti Putra Malaysia. Results: A recently created meso-eutrophic Putrajaya lake had the highest number of rotifer species (11 families and 28 species), followed by the hypereutrophic Sembrong lake (10 families and 24 species). In the acidic-mesotrophic lake, only 17 species of rotifers from nine families were found. In this acidic water-body, Ptygura libera was the most dominant species contributing to 76.1% of the total rotifer abundance. In Putrajaya lake, Keratella cochlearis contributed to 38.0% of rotifer populations followed by P. libera with 33.0%. Brachionus forficula and Brachionus calyciflorus were dominant in Sembrong lake which made up of 41.2% of total rotifer species. Putrajaya lake had highest density of rotifers with a total mean density of 239.4 +/- 30.3 ind. I-1 compared in Sembrong lake (158.7 +/- 16.6 ind. I-1) and Subang lake (58.9 +/- 18.5 ind. I-1). The canonical correspondence analysis (CCA) scores indicated that the abundance of B. calyciflorus and B. forficula was related to the eutrophic condition associated with the high total phosphorus and chlorophyll a. Ptygura libera seemed to be associated in less nutrient rich waters, and seemed to be tolerant to acidic waters. Interpretation: This study illustrated that the dominance of rotifer species was related to the lake health status. The abundance of Brachionus, Keratelia and Trichocerca were related to the eutrophic condition associated with turbidity, total dissolved solid (TDS), chlorophyll a and nutrient concentrations. Ptygura libera seemed to be associated with less nutrient rich water tolerant to acidic waters (pH 4-5).