PS 39-59 - CANCELLED - Is Diversity Dammed? Analysis of Fish Diversity in Dammed and Undammed Estuary Streams Within the Virginia Peninsula Using Environmental DNA (eDNA)

Abstract: Anthropogenic activities are the leading cause to biodiversity decline worldwide. It has been well documented that large dams disrupt dispersal and alter local habitat often leading to less diverse aquatic systems. Yet, it is not well known how much more numerous smaller dams impact fish communities in estuary systems where dispersal is a critical part of the ecosystem. Here we used eDNA (environmental DNA) to assess the alpha, betta, and gamma diversity of fish species within the Virginia Peninsula in the lower Chesapeake Bay to compare diversity between sites with an undammed connection to the estuary to diversity within dammed sites. More than 500 2-Liter samples of water were collected from 35 total sites, 16 undammed creeks and 19 dams. We hypothesized that dams cause a local decrease in fish species richness by degrading local habitat and reduce dispersal by creating barriers. 75 species of fish were documented. Linear regression analysis showed undammed sites had significantly higher alpha diversity by about 10 species per site compared to dammed sites, meaning more species were found in undammed sites. We hypothesized that community composition (beta diversity) of the fish communities between dammed sites and undammed sites would be different due to limitations on dispersal and disconnection from the regional network. Beta dispersion testing showed undammed sites have higher variability in species from site to site. We hypothesized that beta diversity between dammed sites would be low due to biotic homogenization (i.e., all dam ponds species compositions are similar due to similar habitat characteristics of dam ponds). Dammed sites showed similar species composition when compared to one another. Gamma diversity across the landscape showed a lower average of species within dammed sites compared to the average of species within undammed sites. These results suggest that even small dams can disrupt dispersal in estuary networks leading to decreased local diversity within areas of the estuary that would otherwise be connected to the estuary.