GLOBAL PATTERNS OF PHYTOPLANKTON CHANGE ACROSS GRADIENTS OF FLOATING SOLAR ENERGY COVERAGE

Floating photovoltaic (FPV) systems are expanding as countries decarbonize, solar costs fall, and land availability declines. FPV arrays modify light and temperature, potentially affecting stratification, biogeochemistry, and primary production in aquatic ecosystems. While shading is expected to curb algal blooms, the mechanisms and effects on different coverage levels remain uncertain. Using remote sensing, we assessed how FPV coverage relates to phytoplankton abundance, using Normalized Difference Chlorophyll Index (NDCI) as a proxy. For ~500 installations, we mapped FPV footprints and host waterbodies, developed a spectral index for FPV detection, and estimated installation dates. Chlorophyll-a was evaluated from Sentinel-2 MSI NDCI processed on Google Earth Engine. For each FPV site, we compared NDCI medians years before and after installation and contrasted trends with nearby reference waterbodies identified from HydroLAKES, a global database of >1 million natural and artificial lakes. We then computed ΔNDCI to isolate FPV-related effects and quantified FPV coverage relative to lake area. Across the global sample, ΔNDCI was generally small, near zero, at low to moderate coverage, but became slightly negative when FPV occupied >70% of the lake surface. Reductions were stronger in high-chlorophyll than in low-chlorophyll systems. Overall, results indicate that high-coverage FPV arrays modestly reduce phytoplankton relative to nearby non‑FPV lakes. These findings offer new insights into how large-scale, persistent shading influences algal dynamics in freshwater systems.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Aline Valerio, Indiana University (alinedmv@gmail.com)

Authors:

Aline de Matos Valerio, Indiana University  (ademato@iu.edu)

Simone Cardoso, Federal University of Juiz de Fora  (simone.cardoso@ufjf.br)

Etienne Fluet-Chouinard, Pacific Northwest National Laboratory  (etienne.fluet@pnnl.gov)

Steven Grodsky, Cornell University  (grodsky@cornell.edu)

Rafael Almeida, Indiana University  (rafalmei@iu.edu)