Waters provide essential needs both for human societies as well as natural ecosystems. Floating solar PV (FPV) applications on water bodies are currently in strong demand worldwide. Floating solar PV system is a new concept in renewable energy with the solar plants by harnessing available water surface, such in dams, lakes, and other water bodies. Although the floating solar PV industry is becoming more and more popular, the study on the biological, chemical, and physical properties effects of using FPV cover on natural water coverage -especially in tropical countries -has not been widely carried out yet. This paper aimed to evaluate the effect of floating solar PV on temperature, DO (dissolved oxygen), TDS (total dissolved solids), total phosphorus concentration, and chlorophyll-a concentration using mesocosm experiments to understand the biological, chemical, and physical process under closed environment. The experiment was conducted in a natural water body, Mahoni Lake, in which a total amount of 7 water samples were collected from each mesocosms. The results show that the floating solar PV reduces the average temperature, DO, conductivity, TDS, and chlorophyll-a concentration changes (p-value < 0.05); and the floating solar PV does not directly reduce the average total phosphorus concentration due to high probability of thermal stratification (p-value > 0.05).

The applications of floating photovoltaic (FPV) on water bodies are currently on a global demand. Despite the increasing popularity of floating photovoltaic industry, studies on ecological effects of lake coverage using floating photovoltaicespecially in tropical countries -haven't been widely conducted. This study evaluates the effect of floating photovoltaic on dissolved oxygen and trophic state changes in water bodies using mesocosm experiment. Trophic state is an indicator of the degree of transformation and ecological disruption in water bodies. The parameters used to assess trophic index (Trophic State Index, TSI) are total phosphorus, chlorophyll-a, and water transparency. TSI uses mathematical equations to calculate data of the experiments, so that the expression of trophic level can be determined. The mesocosm experiment was conducted from March 25 th to April 15 th 2021 in Mahoni Lake, in which a total amount of 7 water samples were collected from each mesocosms. Our results show that mesocosms with 100% FPV cover have a lower dissolved oxygen (p-value < 0,05) and a lower TSI value (p-value < 0,05) compared to mesocosms without FPV cover (control). According to the TSI value, despite the decrease in TSI value, the trophic state was still classified as eutrophic. The results obtained are an important tool for further studies focusing on water quality and ecology impact regarding FPV on water bodies.