Assessment of benthic invertebrate diversity and river ecological status along an urbanized gradient using environmental DNA metabarcoding and a traditional survey method

Benthic invertebrate diversity is one of the most commonly used bioindicators for assessing aquatic ecosystem health in river systems. Although an increasing number of studies have focused on assessing benthic invertebrate diversity using environmental DNA metabarcoding and traditional survey methods, benthic invertebrate diversity and ecological status assessments performed across different landscapes within river systems have not been well documented. Here, the diversity and ecological status of benthic invertebrates and the influence of water quality on the invertebrate assemblage distribution along an urbanization gradient in rivers from the Jingjinji (JJJ) region, China, were investigated using eDNA metabarcoding and the traditional method. With the combination of the two methods, 395 benthic invertebrates from 6 phyla, 27 orders, 94 families, and 222 genera were identified. The species richness of the benthic invertebrate community in the mountain area was significantly higher than that in the urban and agricultural areas. Compared to the traditional results, eDNA metabarcoding obtained a significantly greater number of species from every sampling site (P = 0.000) and detected a notably higher abundance in Annelida (P = 0.000). Furthermore, the nonmetric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) based on the Bray-Curtis dissimilarity index indicated that the benthic invertebrate communities from the different habitats were discriminated more accurately and easily using eDNA metabarcoding (P = 0.038) than with the traditional method (P = 0.829). Additionally, the assemblages identified by eDNA metabarcoding were more closely linked to water quality and could be realistically used to assess the ecological status of rivers. Our findings highlight that eDNA metabarcoding could represent a rapid and reliable method for estimating benthic invertebrate diversity and ecological status in river systems.