AUTHOR=Cory Rose M. , Davis Timothy W. , Dick Gregory J. , Johengen Thomas , Denef Vincent J. , Berry Michelle A. , Page Sarah E. , Watson Susan B. , Yuhas Kate , Kling George W. 

TITLE=Seasonal Dynamics in Dissolved Organic Matter, Hydrogen Peroxide, and Cyanobacterial Blooms in Lake Erie

JOURNAL=Frontiers in Marine Science

VOLUME=3

YEAR=2016

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2016.00054

DOI=10.3389/fmars.2016.00054

ISSN=2296-7745

ABSTRACT=<p>Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) has been suggested to influence cyanobacterial community structure and toxicity. However, no study has investigated H<sub>2</sub>O<sub>2</sub> concentrations in freshwaters relative to cyanobacterial blooms when sources and sinks of H<sub>2</sub>O<sub>2</sub> may be highly variable. For example, photochemical production of H<sub>2</sub>O<sub>2</sub> from chromophoric dissolved organic matter (CDOM) may vary over the course of the bloom with changing CDOM and UV light in the water column, while microbial sources and sinks of H<sub>2</sub>O<sub>2</sub> may change with community biomass and composition. To assess relationships between H<sub>2</sub>O<sub>2</sub> and harmful algal blooms dominated by toxic cyanobacteria in the western basin of Lake Erie, we measured H<sub>2</sub>O<sub>2</sub> weekly at six stations from June to November, 2014 and 2015, with supporting physical, chemical, and biological water quality data. Nine additional stations across the western, eastern, and central basins of Lake Erie were sampled during August and October, 2015. CDOM sources were quantified from the fluorescence fraction of CDOM using parallel factor analysis (PARAFAC). CDOM concentration and source were significantly correlated with specific conductivity, demonstrating that discharge of terrestrially-derived CDOM from rivers can be tracked in the lake. Autochthonous sources of CDOM in the lake increased over the course of the blooms. Concentrations of H<sub>2</sub>O<sub>2</sub> in Lake Erie ranged from 47 ± 16 nM to 1570 ± 16 nM (average of 371 ± 17 nM; <italic>n</italic> = 225), and were not correlated to CDOM concentration or source, UV light, or estimates of photochemical production of H<sub>2</sub>O<sub>2</sub> by CDOM. Temporal patterns in H<sub>2</sub>O<sub>2</sub> were more closely aligned with bloom dynamics in the lake. In 2014 and 2015, maximum concentrations of H<sub>2</sub>O<sub>2</sub> were observed prior to peak water column respiration and chlorophyll <italic>a</italic>, coinciding with the onset of the widespread <italic>Microcystis</italic> blooms in late July. The spatial and temporal patterns in H<sub>2</sub>O<sub>2</sub> concentrations suggested that production and decay of H<sub>2</sub>O<sub>2</sub> from aquatic microorganisms can be greater than photochemical production of H<sub>2</sub>O<sub>2</sub> from CDOM and abiotic decay pathways. Our study measured H<sub>2</sub>O<sub>2</sub> concentrations in the range where physiological impacts on cyanobacteria have been reported, suggesting that H<sub>2</sub>O<sub>2</sub> could influence the structure and function of cyanobacterial communities in Lake Erie.</p>