Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin and a Planktothrix spp. bloom in Sandusky Bay. Recently, USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate P and nitrogen (N) limitation of biomass and cyanotoxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystins under nutrient repletion with slight induced P limitation under 40% dilutions, and the Sandusky Bay bloom produced anatoxin under N limitation in both dilution treatments. The results demonstrate the importance of recognizing spatiotemporal heterogeneity in nutrient limitation in aquatic systems and to properly combat cyanotoxin production in WLE, both N and P reduction efforts should be implemented in the WLE watershed.

Nutrient limitation dynamics of western lake erie cyanoHAB biomass and toxin production

ACS Spring Meeting 2021

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