Reduced forms of nitrogen are a driver of non-nitrogen-fixing cyanoHABs and toxicity in Lake Erie

Session: 41a. - Great Lakes Harmful Algal Blooms Research from Watershed Influence to Ecosystem Effects

Silvia Newell, Wright State University, [email protected]
Timothy Davis, Bowling Green State University, [email protected]
Thomas Johengen, CILER, University of Michigan, [email protected]
Duane Gossiaux, NOAA GLERL, [email protected]
Ashley Burtner, CILER - University of Michigan, [email protected]
Danna Palladino, CIGLR, [email protected]
Mark McCarthy, Wright State University, [email protected]

Abstract

Western Lake Erie (WLE) experiences anthropogenic eutrophication and annual, toxic cyanobacterial blooms of non-nitrogen (N) fixing Microcystis. These blooms have been correlated with an increased proportion of soluble reactive phosphorus loading from the Maumee River. Here, we show that the proportion of the annual Maumee River N load of non-nitrate N, or total Kjeldahl nitrogen (TKN), has also increased significantly (p = 0.001) over the last few decades and is also significantly correlated to cyanobacterial bloom biomass (p = 0.003). We also compared the ratio of chemically reduced N to oxidized N (TKN:NO3) concentrations to extracted chlorophyll and phycocyanin concentrations from all stations within the NOAA GLERL weekly monitoring in WLE from 2009-2015. Both chlorophyll (p < 0.0001) and phycocyanin (p < 0.0001) were significantly correlated with TKN:NO3. This correlation between the increasing fraction of chemically reduced N from the Maumee River and increasing bloom biomass demonstrates the urgent need to control N loading, in addition to current P load reductions, to WLE and similar systems impacted by non-N-fixing, toxin-producing cyanobacteria.

1. Keyword
Lake Erie

2. Keyword
cyanophyta

3. Keyword
eutrophication

4. Additional Keyword
nitrogen

5. Additional Keyword
Maumee River