The Southeastern US is a global hotspot for freshwater biodiversity with the Mobile River Basin harboring some of the richest freshwater diversity in the world. In 2016, this region was under one of the most extreme flash droughts in at least 10 years. In Alabama, exceptional drought conditions started in September 2016 and persisted unabated until late December 2016, drying numerous waterways with many large rivers reading 5% or less of historic flows. How aquatic organisms respond to atypical and quickly-occurring disturbances such as flash droughts has been unclear. We hypothesized that the ability to use a downstream refuge during drought is a bottleneck that varies in significance based on species' vagility and network position. Using recently developed regional ecological endpoint curves developed for effective stream restoration for the Piedmont of Alabama and for the Appalachian Plateau of north Alabama, we determined local community compositional shifts in response to drought and evaluated the effect of disturbance on ecological endpoint curves. In summer 2017 fish and crayfish were collected post-drought within representative reaches of 18 Piedmont and 17 Appalachian Plateau streams ranging from 0.05 – 261 km2 drainage area using a Smith-Root LR-24 backpack electrofisher.
Results/Conclusions
Data suggest that fish assemblage structure and ecological endpoint curves were not different post-drought. Fish species richness, Shannon Diversity, and fish total catch all increased with drainage area but metrics were not significantly different from pre-drought conditions (p>0.05). Redunancy analysis suggest there was no compositional change in fish assemblages post drought. These preliminary findings suggest that fish were minimally influenced by drought and that regional ecological endpoint curves are robust to such disturbances.