2023 Volume 26 Pages 15-24
The cumulative ecological risks from multiple herbicides in Japanese rivers were evaluated using species sensitivity distribution and were compared with natural periphytic diatom communities. Region-specific predicted environmental concentrations were estimated at 9 rivers considering the region-specific parameters of environmental conditions. Then the multi-substance potentially affected fraction (msPAF) was calculated as a risk index of multiple herbicides using the computation tool NIAES-CERAP. On the other hand, river ecological survey focusing on diatom community were conducted in these 9 rivers and several biological metrics for species composition were calculated such as genus number, Shannon’s diversity, DAIpo, and SPEARherbicides which is an indicator of the herbicide effect on the diatom community. DAIpo and SPEARherbicides (but the population number of each genus was not log-transformed) significantly correlated with msPAF, indicating the applicability of these metrics for assessing the effect of herbicide mixture. Moreover, the percentage of abundance for genus Planothidium and Nitzschia were significantly correlated with msPAF negatively and positively, respectively.
