Synthesis of Upper Mississippi River System submersed and emergent aquatic vegetation: past, present, and future

Abstract

Altered hydrology resulting from the presence of locks and dams and erosive agricultural land use practices have created conditions that have impacted the growth, distribution, and survival of aquatic vegetation on the Upper Mississippi River System (UMRS). Three inter-related abiotic factors (light transparency, nutrients, and sedimentation) worsened by impoundment and erosive agricultural practices, have played a major role in widespread submersed macrophyte loss in the UMRS. Aquatic vegetation provides food and shelter for biota as well as impacting water quality. Successful efforts to restore aquatic macrophytes on the UMRS have focused on habitat restoration construction projects and water-level management drawdowns. Currently, the status of aquatic vegetation varies within the UMRS, with most of the aquatic vegetation being found between lower Pool 4 (below Lake Pepin) and Pool 13. Although aquatic macrophytes have varied among locations over the past 17 years, an increase in aquatic plants was apparent in 2007 and 2008. Very little research regarding the role of moist soil and emergent vegetation and their responses to ecological factors has occurred within the UMRS. Future research efforts must continue to focus on understanding the ecological and anthropogenic impacts to all aquatic macrophytes within the landscape of one of the largest river systems in the world.