2026 Volume 49 Pages 65-74
The installation of floating photovoltaics (FPV) on water surfaces has increased in recent years; however, their effects on water quality remain poorly understood. In this study, we evaluated the effects of FPV on cyanobacterial bloom in irrigation ponds through field surveys of existing FPV installations. In eight FPV-equipped ponds in Japan, summer surface chlorophyll-a (Chl-a) concentrations showed a weak negative correlation with FPV coverage (r = −0.38) . High-frequency monitoring and short-term experiments were conducted at the Shiroinuma Reservoir, where cyanobacterial bloom occurs. Under an FPV system, photosynthetic oxygen production decreased to approximately one-tenth of that in the adjacent open water, whereas surface Chl-a concentrations were higher than those in uncovered areas. This pattern is attributed to the combined effects of reduced photosynthesis and growth as a result of shading and the accumulation of surface water and suspended particles beneath the FPV owing to water temperature differences and wind sheltering. Diurnal variations in pH and dissolved oxygen were governed primarily by solar radiation and water residence time, with only minor spatial differences. Overall, the installation of FPV in irrigation ponds in Japan may contribute to cyanobacterial bloom control without inducing a pronounced deterioration in local water quality.
