Seasonal and Spatial Variation of Ciliate Abundance in Lake Lanao along Wato-Balindong, Lanao Del Sur, Philippines

Abstract

Abstract Ciliated protozoans are one-celled eukaryotes characterized by hair-like structures called cilia. Ciliate abundance has been used as bioindicators of organic pollution in a freshwater system. This study was conducted to determine the spatio-temporal variation of ciliate abundance in Lake Lanao, Philippines, along Wato-Balindong’s littoral and pelagic zones during dry (May 2018) and wet (August 2018) seasons. It intended to assess the trophic state of the lake based on planktonic ciliate abundance. In each zone, three sites were sampled for ciliates using a conical plankton net. The ciliates were fixed with formalin-acidified logul’s Iodine for microscopic observation and counting. Spatially, the data on ciliate abundance did not vary between littoral and pelagic zones. However, it did vary significantly between seasons; ciliates had higher abundance in the wet season than in the dry season. This variation could be attributed to a possible increase of nitrogen and phosphorus washed into the lake by rain. Bioindication using ciliate abundance revealed that Lake Lanao in Wato-Balindong is ultraoligotrophic, i.e., the lake is pristine, well-oxygenated and low in nutrients during sampling.