Putting eDNA to the test: A field comparison of eDNA metabarcoding to established protocols for assessing biodiversity in Missouri's Ozark Highland streams

Abstract

Aquatic biodiversity monitoring to inform conservation and management efforts in-stream systems has increasingly begun to incorporate environmental DNA (eDNA)-based sampling methods. We conducted a comparison of eDNA metabarcoding to a traditional protocol of combined seining and electrofishing methods to assess fish biodiversity of wadeable stream sites in six separate drainages in the Ozark Highlands of Missouri (USA). The study further focused on the headwaters of the Meramec River, which included 11 sites and seasonal sampling (summer and winter). We compared estimates of diversity across sampling methods, assessed the influences of water flow (depth, velocity, and discharge) and season, and tested the effects of sampling method and site locality on fish assemblage composition. eDNA sampling detected approximately double the number of species compared to traditional methods, providing higher diversity estimates while maintaining the relative ranking of sites. eDNA detection probabilities were positively associated with stream depth and velocity and were generally higher in summer than in winter but not for all species. Estimated species richness was positively associated with discharge for both methods but the relationship was stronger with eDNA sampling. Assemblage differences between tributary and mainstem sites were attributable to a small number of species that were found predominantly in one stream size category or the other, indicating that eDNA was sensitive to within-drainage assemblage structure relationships. We highlight improved species detection, a more comprehensive understanding of assemblage structural dynamics, and the potential ability to integrate data across sampling methods as important benefits that encourage the use of eDNA metabarcoding as a primary collection method in future stream biodiversity assessment and monitoring programs.