Higher methanotroph abundance and bottom-water methane in ponds with floating photovoltaic arrays
Floating photovoltaic (FPV) arrays alter the methane (CH 4 ) cycling dynamics of waterbodies on which they are deployed. Here, we investigated dissolved CH 4 dynamics and associated CH 4 cycling microbial communities (methanogens and methanotrophs) in the second year of FPV deployment (70% aerial coverage) in experimental ponds. We found that bottom-water CH 4 concentrations were twice as high in ponds with FPV compared to those without, while surface water CH 4 concentrations were orders of magnitude lower than bottom-waters, but did not differ between treatments. There was no change in the relative abundances of putative sediment methanogens or methanotrophs, but FPV restructured methanogen communities. FPV promoted late-summer methanotroph blooms in the water column, with abundances surpassing 1,000,000 cells mL -1 . We conclude that prolonged periods of CH 4 production in low oxygen FPV ponds favored blooms of methanotrophs, that may mitigate diffusive CH 4 emissions to the atmosphere by consuming dissolved CH 4 .