Evaluation of Habitat Preferences of Invasive Macrophyte Egeria densa in Different Channel Slopes Using Hydrogen Peroxide as an Indicator

is an often-found invasive species in Japan, which has spread widely in the past two decades in rivers where no macrophytes had previously been found. As a result, these ecosystems have now become dominated by . . The habitat preference for . colony formation was investigated using the tissue concentrations of hydrogen peroxide (H O : a reactive oxygen species) under varying conditions in rivers and laboratory conditions. The empirical equations that can describe the macrophyte tissue H O formation under various velocity and light conditions were produced. The H O concentrations of dark-adapted plants are proportional to the flow velocity, and the surplus H O concentration in the light-exposed condition corresponded to the photosystems produced H O . When the H O concentration exceeds 16 μmol/gFW, plant tissue starts to deteriorate, and biomass declines, indicating the critical values required for long-term survival of the plant. The empirically obtained relationships between flow velocity or light intensity and the analysis of H O concentration for different slopes and depths of channels found that the H O value exceeds the critical H O concentration in channels with above 1/100 at around 0.6 m depth. This agrees with the observed results where colonies were not found in channels with slopes exceeding 1/100, and biomass concentration was the largest at depths of 0.6 to 0.8 m. H O concentration is quite applicable to understanding the macrophyte condition in various kinds of macrophyte management.