The effects of anthropogenic disturbance on ecosystem structure and function in Coastal Plain streams in the southeastern United States

Abstract

Widespread development fueled by economic growth continues to stress aquatic resources. The world continues to both urbanize and deal with the effects of climate change. In the Southeastern United States, more frequent and intense rainfall events, coupled with increased runoff from urban areas, threaten headwater and coastal aquatic ecosystems. This research assesses how headwater ecosystems respond to restoration intended to reduce the effects of watershed disturbance, and to understand how tidal creek ecosystems respond to coastal watershed development. In my first study, I found that coarse woody debris dam restorations were not effective 14-15 years after restoration at increasing ecosystem functional rates and did not reduce total suspended solids or nutrient concentrations. Further, the effects of watershed disturbance were still apparent following restoration. In my second study, I found that coastal watershed development led to increased salinity variability in tidal creeks associated with freshwater runoff, and that this reduced ecosystem respiration. In my third study, I found that salinity variability led to lower abundance of a tidal creek fish, Fundulus grandis, but that abundance increased with mean site salinity. I found that salinity at a subset of my study sites decreased between 2012 and 2020, and this likely drove the observed decrease in F. grandis abundance between 2012 and 2020. In my fourth study, I found that F. grandis diets were broad and appear to be robust to changes in the watershed. Taken together, my research highlights that 1) restoration is likely to be insufficient if disturbance in the watershed is not addressed, 2) even low levels of disturbance can lead to detectable changes in ecosystem function, and 3) changes in climate and land use are leading to reduced F. grandis abundance, with implications for energy transfer from tidal creeks.