eDNA Biomonitoring of Macroinvertebrate Communities for the Bioassessment of a River's Ecological Status

Environmental DNA (eDNA) becomes a promising technology for macroinvertebrate monitoring worldwide. In recent decades, with increasing humanization processes, such as water pollution and habitat fragmentation, the richness and abundance of macroinvertebrates show a dramatic decline, which is particularly evident in tropical or subtropical rivers. The high-throughput and rapid monitoring of species' survival and the ecological status of their habitats are relevant to river management. Here, we used the eDNA technology to detect macroinvertebrates in the Dongjiang River-a typical subtropical river in Southern China, to assess the ecological status, based on eDNA datasets. Our data showed a total of 640 OTUs detected by eDNA technology, belonging to three phyla, five classes, 13 orders, 33 families and 71 genera of macroinvertebrates, and these taxa had a 36.6% coverage rate with historical data at the genus level. The traditional water quality index (WQI) showed that the upstream of Dongjiang River were mainly levels I similar to II, the middle stream were levels II similar to III, and the downstream were levels IV similar to V. The eDNA-based biotic indices showed almost the same findings, that is, the overall ecological status of Dongjiang River was: upstream > middle reaches > downstream. Overall, this study provides important datasets and technical support for eDNA technology in macroinvertebrate monitoring and ecosystem management in the subtropical rivers.