THE COMPLEMENTARY ROLE OF DETRITUS IN ENVIRONMENTAL DNA MONITORING OF MACROINVERTEBRATES: A CASE STUDY IN QINGYI RIVER

In order to explore the differences in monitoring macroinvertebrate diversity using environmental DNA (eDNA) technology across different sample types, water and detritus samples were collected from the Qingyi River Basin in May 2023 and analyzed by using traditional morphological method. The results showed that eDNA technology detected 692 operational taxonomic units (OTUs), belonging to 3 phyla, 6 classes, 64 families, and 158 genera. Specifically, water samples identified 416 macroinvertebrates OTUs, belonging to 3 phyla, 5 classes, 46 families, and 117 genera, while detritus samples identified 435 macroinvertebrates OTUs, belonging to 3 phyla, 6 classes, 54 families, and 122 genera. In contrast, the morphological method detected 66 macroinvertebrate species, belonging to 3 phyla, 7 classes, and 42 families. Compared to the morphological method, eDNA technology exhibited significantly higher detection capabilities at the family and genus levels, though morphological method performed better in detecting gastropod species. Principal Coordinate Analysis (PCoA) revealed significant differences in the macroinvertebrate community structure between water and detritus samples, with complementary species detection between the two sample types. Linear regression analysis indicated a significant decline in species richness detected by eDNA (combining water and detritus samples) from the headwaters of river to its downstream regions, whereas species richness detected by morphological methods showed no significant variation. In eDNA surveys, water samples are a commonly used sample type; our study demonstrates that detritus can serve as an effective complement to water, laying the foundation for the standardized application of eDNA technology.