Documenting Emerging Insects, Environmental DNA, and Metal Concentrations in a Small Appalachian Stream

Accurately documenting aquatic insects is of the utmost importance given recent proposals for a paradigm shift in conservation to protect less-charismatic species that are necessary for ecosystem functioning. We used both field techniques and molecular methods to assess biodiversity in a stream in southwest Virginia. We used emergence traps to collect organisms that emerged from the stream as reproducing adults over a 4-week period and collected environmental samples (e.g., water, sediment) to sequence the DNA found in the samples. Emerging aquatic insect abundance, richness, and diversity increased over time. More family richness was detected using environmental DNA (eDNA) than traditional field sampling; however, many families detected using field techniques were not recovered using eDNA, furthering support that both protocols are necessary for fully documenting biodiversity. We did not have much success in identifying eDNA sequences to species with high sequence similarity, suggesting that invertebrate biodiversity of southwest Virginia is not well-documented in open-source DNA sequence databases. In addition to documenting insect biodiversity, we measured the levels of heavy metals in the stream sediment. Sediment values for cadmium, chromium, copper, mercury and lead were within regulatory limits and were not significantly correlated with biodiversity measures.