Long-term seasonal and temporal changes of hydrogen peroxide from cyanobacterial blooms in fresh waters.

In water, hydrogen peroxide (HO) is produced through abiotic and biotic reactions with organic matter, including algal cells. The production of HO is influenced by harmful algal cell communities and toxicity. However, only a few studies have been conducted on HO concentrations in natural water. Particularly, the seasonal and temporal patterns of HO concentration suggest that HO generation from aquatic microorganisms could be identified to compare of photochemical production from dissolved organic matter. Study area is a source of raw water and is a large artificial lake located near a metropolitan city. Due to various environmental conditions, harmful algal blooms frequently occur in summer. The purpose of this study was to trace the HO concentration and water quality parameters of study area where algal bloom occurs and what factors directly affect the HO concentration. Experiments were performed on the influencing factors via water samples from study area and lab-scale culture tank. The lake produces an average of 553 nM HO, which increases by more than three times (1460 nM) in summer compared the winter. The lake (18.6-23.8 nMh) produced more HO than streams (7.4-9.0 nMh) during daylight hours. All water sites presented the lowest production rates in dark conditions (1.1-1.5 nMh). Daytime environment increased the generation rate more than the nighttime. The trend of HO produced by algal cells was similar to that of the growth of algal cells. The exposure to external substances (heavy metals and antibiotics) increased the incidence by approximately five times; antibiotics were more influential than heavy metals.