Abstract: The connectivity of streams that allow flow and exchange of water, organisms, sediments, organic matter, nutrients, and energy in riverine environments is important for sustaining associated ecological processes. The Apalachicola River and its associated floodplain and estuary are integral components of the regional hydrologic and ecological systems of the Gulf Coast. Hydrologic connectivity between the river channel, slough, and the surrounding floodplain is critical for the transport of nutrients, organic matter, and energy, which are necessary for ecosystem functioning. However, years of river management actions have resulted in reduced flow through many of the sloughs in the middle reach of the Apalachicola River, leading to decreased nutrient transport to downstream estuaries and floodplain swamps. This study compares the hydrology and chemistry of three sloughs along the Apalachicola River to determine the ecological effects of sand accumulation resulting due to river management actions. The study used field data collection, multivariate statistical analysis, and HEC model. The specific objectives of the study were to compare the hydrology and chemistry of the three sloughs along the Apalachicola River and to determine the ecological impacts of decreased flow through the sloughs and the associated floodplain swamps. The results show that as streamflow in the main river recedes, flow through Spider Slough, and Douglas Slough recedes to intermittence, causing the water level to decline and flow to drop to 0 in Spider and Douglas Slough. This affects the water chemistry of the slough to DO 2-3 mg/l and receiving floodplain swamp. When the slough has disconnected from downstream floodplains entirely, nutrient delivery to the estuary and swamp communities in the river’s floodplain are impacted. The findings suggest that knowledge of ecosystem function in response to varying streamflow conditions is necessary for the ecology of slough systems. Therefore, management actions that restore hydrologic connectivity and remove sand accumulation in the sloughs may be necessary to preserve the ecological health of the Apalachicola River and its associated ecosystems. The findings emphasize the importance of restoring hydrologic connectivity to maintain the ecological health of the river and its associated ecosystems. This study's results may serve as a foundation for future studies and management actions that aim to preserve the health and function of riverine ecosystems in the Gulf Coast region.
