Analysis of aquatic insect and diatom communities using environmental DNA and its application to ecological effect assessment of pesticides

Abstract

A methodological investigation was conducted for analyzing the natural communities of aquatic insect and diatom using environmental DNA metabarcoding, followed by the application for ecological effect assessment of pesticides. Water samples were collected from two distinct sites: the Yamaguchi River, as an unpolluted environment, and the Kokai River, characterized by the widespread presence of paddy fields and potentially elevated pesticide concentrations. In consideration of the pesticide effect on riverine ecological communities, the analysis focused on aquatic insect, known to be vulnerable to insecticides, as well as attached diatoms with susceptibility to herbicides. The Yamaguchi River generally exhibited higher values of bioindicators compared to the Kokai River, supporting the promising role of the environmental DNA approach in assessing ecological effect within natural aquatic ecosystems. An advantage of this methodology lies in its capacity for concurrent use alongside environmental monitoring of chemical substances. Ideally, future monitoring should encompass the simultaneous analysis of chemical concentrations and biota.