Floating photovoltaics restructure microbial communities through sustained light reduction and oxygen limitation

Floating photovoltaic (FPV) systems are expanding rapidly on inland waters and offer major potential as renewable energy infrastructure. Yet their long-term ecological impacts on aquatic microbial communities remain poorly understood. We conducted a two-year whole-ecosystem manipulation in experimental ponds to test how sustained FPV coverage alters microbial abundance, community structure, and metabolic functional potential. We hypothesized that FPVs would reduce light and dissolved oxygen, suppressing oxygenic photoautotrophy and promoting anaerobic metabolism. Integrating 16S rRNA amplicon sequencing, water chemistry, and flow cytometry-derived cell abundances, we show that FPV coverage drives persistent hypoxia and light limitation, restructuring microbial communities in both the water column and sediments. FPVs strongly suppressed oxygenic photosynthesis by planktonic cyanobacteria and enriched benthic cyanobacteria and anoxygenic phototrophs, including green sulfur and non-sulfur bacteria. Methanotrophs increased modestly in 2023 but expanded by an order of magnitude in 2024 as hypoxia and methane accumulation intensified reductive metabolism. Sediments similarly exhibited a shift from oxygenic to anoxygenic phototrophy. Together, these persistent changes indicate a metabolic regime shift toward an alternative stable state. Our findings demonstrate that FPVs function as a long-term press disturbance that restructures aquatic microbial communities and biogeochemical cycling potential, underscoring the need to consider microbial responses in FPV design and management.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Sophia Aredas, Cornell University (sna49@cornell.edu)

Authors:

Sophia Aredas, Department of Microbiology, Cornell University  (sna49@cornell.edu)

Sophia Richter, Department of Biological Sciences, Notre Dame University  (srichte2@nd.edu)

Nicholas Ray, School of Marine Science & Policy, University of Delaware  (nickray@udel.edu)

Meredith Holgerson, Department of Ecology and Evolutionary Biology, Cornell University  (meredith.holgerson@cornell.edu)

Steven Grodsky, U.S. Geological Survey, New York Cooperative Fish and Wildlife Research Unit & Department of Natural Resources and the Environment, Cornell University  (grodsky@cornell.edu)

Marian Schmidt, Department of Microbiology, Cornell University  (marschmi@cornell.edu)