Abstract

This paper is a research inquiry on the seasonal change in the structure of the phytoplankton community of the freshwater lakes with a focus on the environmental changes affecting the changes in the form of temperature, light intensity, and nutrient levels. The aim of the study consisted of assessing the seasonal changes of abundance, diversity, and composition of phytoplankton, and correlating the changes with the significant environmental parameters. There were four seasons during which the sampling was performed in the spring, summer, autumn, and winter seasons, with varying trophic status in the freshwater lakes. Temperature, pH, light, and nutrient content and concentration on site were measured; phytoplankton material was identified and enumerated according to standard microscopic procedures. The statistical result revealed that the phytoplankton abundance was most abundant in the warmer months, i.e., 7,500 cells/mL in spring and 12,000 cells/mL in summer, with the dominance of the diatoms and green algae. Quite the contrary, phytoplankton diversity and abundance were less in winter, with a maximum of 4,000 cells/mL. The results showed the strong influence of the light and the nutrient content, particularly nitrogen, on the community structure, in which the higher the degree of light and nutrient content, the higher their diversity and abundance. It requires another investigation to investigate the trends of long-term phytoplankton dynamics, especially during climatic changes, in order to obtain predictive models of the algal explosions and also the control of the ecosystems. Additionally, by including more variables of the environment and more complex statistical models, perhaps would have gained more insight into the complex workings that take place in aquatic environments and how they respond to seasonal and anthropogenic changes.

Keywords: Phytoplankton, Seasonal variation, Freshwater lakes, Algal diversity, Diatoms, Green algae, Environmental factors, Water quality