Vegetation, invertebrate, and fish community response to past and current flow regulation in floodplains of the Savannah River, Southeastern USA

Abstract

In 2005 and 2006, the United States Army Corps of Engineers released experimental flows to mimic natural spring flooding on the highly regulated lower Savannah River in the Southeastern US. We used vegetation, invertebrate, and fish communities to assess how past regulation and current experimental releases were affecting the ecological conditions on floodplains. The nearby Altamaha River, of similar size but retaining near-natural spring pulses, served as a reference. We did not find that past flow regulation of the Savannah River had significantly altered floodplain forest structure. However, numbers of tree seedlings in bottomland hardwood forests were higher during a year with an artificial pulse than one without. Analyses of invertebrate and fish communities suggested some limited differences in floodplain community structure between rivers, with differences being most pronounced for predaceous Dytiscidae beetles and Esox spp. fishes. Artificial re-creation of small spring flood pulses down the Savannah River in 2005 and 2006 elicited some responses from fish and invertebrates, but did not shift species assemblages towards those occurring on Altamaha River floodplains.