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SFS Annual Meeting

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CYANOBACTERIAL BLOOMS IN OLIGOTROPHIC LAKE SUNAPEE, NH, AND THEIR IMPLICATIONS FOR LAKE PHOSPHORUS CYCLES

Cyanobacterial blooms are on the rise worldwide, including in economically important, low nutrient, clear-water (LNCW) lakes where they have not historically been reported. Because cyanobacteria can transport sediment phosphorus (P) into the water column during recruitment from benthic resting stages, we hypothesized that cyanobacterial blooms are key sources of P to LCNW lakes during the summer stratified season. We tested this hypothesis in oligotrophic Lake Sunapee, New Hampshire, by comparing P loading by the large colonial cyanobacterium Gloeotrichia echinulata to external P loading via 11 tributaries during summers 2005-2017. Depending on assumptions, our estimates of potential P loading via Gloeotrichia recruitment range from <0.1 to ~3 kg P/summer. Although this represents a small fraction of the estimated annual P loading via streamflow (~800-2100 kg), cyanobacteria-mediated P loading occurs during late summer when external loading is much lower (~1-3 kg for each of the 5 smaller inflows vs. 6-25 kg for the larger ones). Given that cyanobacteria-derived P can fuel growth of other phytoplankton and decrease resilience to external perturbations, scientists and lake managers should consider the potential impacts of internal recycling by cyanobacteria on P cycles in oligotrophic lakes.

Kathryn Cottingham (Primary Presenter/Author), Dartmouth College, kathryn.l.cottingham@dartmouth.edu;


Nicole Ward (Co-Presenter/Co-Author), Virginia Tech, nkward@vt.edu;


Bethel Steele (Co-Presenter/Co-Author), Cary Institute of Ecosystem Studies, steeleb@caryinstitute.org;


Holly Ewing (Co-Presenter/Co-Author), Bates College, hewing@bates.edu;


Kathleen Weathers (Co-Presenter/Co-Author), Cary Institute of Ecosystem Studies, weathersk@caryinstitute.org;


Cayelan Carey (Co-Presenter/Co-Author), Virginia Tech, cayelan@vt.edu;