Controls on the photochemical production of hydrogen peroxide in Lake Erie.

In Lake Erie, toxin-forming harmful algal blooms (HABs) occur following high concentrations of hydrogen peroxide (HO). Correlation between HO concentrations and HABs revealed knowledge gaps on the controls of HO production in Lake Erie. One way HO is produced is upon absorption of sunlight by the chromophoric fraction of dissolved organic matter (CDOM). Rates of this photochemical production of HO may increase in proportion to the apparent quantum yield of HO () from CDOM. However, the for HO production from CDOM remains too poorly constrained to predict the magnitude and range of photochemically produced HO, particularly in freshwaters like Lake Erie. To address this knowledge gap, the was measured approximately biweekly from June-September 2019 in the western basin of Lake Erie along with supporting analyses (, CDOM concentration and composition). The average in Lake Erie was within previously reported ranges. However, the varied 5-fold in space and time. The highest was observed in the Maumee River, a tributary of Lake Erie. In nearshore waters of Lake Erie, the decreased about five-fold from June through September. Integration of the controls of photochemical production of HO in Lake Erie show that the variability in rates of photochemical HO production was predominantly due to the . In offshore waters, CDOM concentration also strongly influenced photochemical HO production. Together, the results confirm prior work suggesting that photochemical production of HO contributes but likely cannot account for all the HO associated with HABs in Lake Erie.