EFFECTS OF STREAM CHANNELIZATION AND OTHER GEOMORPHIC ALTERATIONS ON NUTRIENT PROCESSING IN OHIO RIVER TRIBUTARY ECOSYSTEMS

While nutrients such as nitrogen and phosphorus are vital for plant and animal growth, a surplus of these elements stemming from anthropogenic sources in upstream watersheds adversely affects the status of local and large-scale aquatic systems. Nutrients accumulate in smaller streams and travel to larger bodies of water, where nutrient excess can lead to the formation of hypoxic conditions. Ohio River tributary ecosystems, defined as the transition zones where smaller streams flow into the Ohio River, are integral components of their surrounding environments and provide important benefits and services to the human population, such as nutrient uptake and processing. These ecosystems are distinctly located in areas of confluence and experience bidirectional flow from upstream water movement and from Ohio River backflow. Thus, the ecological function and nutrient processing abilities of these streams are affected by stressors derived from both of these hydrologic sources, as well as from alterations in local geomorphology such as stream channel modifications. Withal, it is not fully understood as to what extent geomorphic alterations affect the biological activity and nutrient processing capabilities of tributary environments. To reduce nutrient outputs to the Ohio River and to inform restoration efforts for degraded streams, a clearer understanding of stream channelization and its impacts on the natural function of Ohio River tributaries is warranted. With this regard, water chemistry data and geomorphology information were obtained from twelve randomly selected streams from Kentucky and Indiana that flow into the McAlpine Lock of the Ohio River. Preliminary results suggest that more nutrient processing occurs in channels with less modified geomorphology and slower water movement. Restoration of altered landscapes and channelized streams back to their natural conditions may prove beneficial in improving the quality of local streams and reducing nutrient output to larger aquatic ecosystems.