This proposal is prepared in response to the devastating floods in Eastern Iowa and nearly the entire Upper Mississippi River (UMR) basin during May-July 2008. In UMR Pool 16, above Lock and Dam 16 at Muscatine, Iowa, waters abruptly rose from a highly managed stage of approximately 10 feet to 20 feet and then to nearly 24 feet from May-June 2008. This historic flood event coincided with intense spring cultivation and nutrient application activities in the heavily farmed landscape of the Upper Midwest resulting in a significant pulse of agricultural contaminants to the UMR system. This has led scientists to predict an almost unprecedented delivery of sediment and nutrients to Pool 16, the broader Mississippi River and the Gulf of Mexico. This event presents a unique, and short-lived, opportunity to test scientific hypotheses related to a highly perturbed, large river ecosystem. This ecosystem of braided channels and natural backwaters is already known to inadequately process nutrients such as nitrate to the degree required to protect the Gulf from hypoxic episodes. Extreme, flood-related sediment deposition almost certainly impacts the nutrient processing cycle in the short and long term. It is also known that mussels and bacteria play a major role in nutrient cycling in the broad food web containing phytoplankton, zooplankton, microzooplankton, dissolved & particulate organic matter, and benthos. Given this confluence of events, and the importance of understanding nutrient cycling, we wish to test the following hypothesis: Intense deposition of particulate organic matter from extreme flooding alters the freshwater mussel and microbial food webs through physical and chemical means. Immediate Need: The principal investigators feel this hypothesis can only be tested via the quickresponse Small Grants for Exploratory Research (SGER) funding mechanism since the highly perturbed ecosystem in question is actively returning to more steady-state conditions. The research team must be deployed very soon to study the perturbed nitrogen cycling rates such that comparisons with baseline nitrogen processing rates can be made in the future. Broader Impacts: Floods occur around the world on a regular basis, but the frequency and extremity of these events will increase given the influence of global climate change. This research will contribute to the development of a ?theory of floods? that is proposed by colleagues at the University of Iowa. This theory will seek to unify research related to hydrology, ecology, socio-economic, environmental and human consequences and influences on flooding. The impact of such research can be expressed in billions of dollars, millions of acres of habitat, thousands of species, and centuries of human enjoyment. Intellectual Merit: This research will expand our knowledge of large river nutrient processing dynamics resulting from extreme flooding events and during baseline moments. Abrupt changes in nutrient loading and extreme shifts in algal compositions can influence food quality which may adversely affect desirable and invasive freshwater mussels. This work will further characterize the relation between nutrient conditions and food quality for mussels and other biota in an important reach of the Upper Mississippi River. Water quality, nutrients, and their effects of biological processes are key management concerns in the Upper Mississippi River.
