Linking community and food-web approaches to restoration:

An ecological assessment of created and natural marshes influenced by river diversions.

Science Overall goals, objectives and implications

Goal: This project will investigate how river diversions influence the living communities, food web structure, and function of created versus natural marshes to inform the development of marsh restoration strategies.

Our concerns: Coastal land loss in Louisiana has claimed more than 4,800 km2 since the 1930s. Restoration efforts include modifying hydrologic patterns and construction of tidal marshes and river diversions to reconnect the Mississippi River to adjacent estuaries. While these restoration efforts have shown promise for reducing land loss, little is known about their impacts on the composition of the plants and animals in a coastal marsh and their food web structure.

Our goals: Our research seeks to expand knowledge of the effects of river diversions on natural versus created marshes in Louisiana. Researchers will determine species composition, abundances, and food web structure in natural marshes along varying levels of salinity that result from a river diversion. We will also examine species composition, abundances, and food web structure in created marshes that differ in age influenced by this same river diversion. Finally, the data collected from the marshes will be incorporated into an ecosystem model to predict the impact of salinity changes and habitat restoration efforts on marsh food web structure, function, and resilience.

Expected Outcome: This project will increase understanding of how river diversions impact the marsh food webs and provide the means for predicting how certain types of restoration will impact the species living in a marsh. This project will allow managers to take an end-to-end ecosystem perspective when making management decisions.

The Team: Michael J. Polito (Lead Investigator, Louisiana State University, mpolito@lsu.edu), Annette S. Engel (University of Tennessee-Knoxville), Linda M. Hooper-Bui (Louisiana State University), Olaf P. Jensen (Center for Limnology, University of Wisconsin – Madison, formerly Rutgers University), Paola Lopez-Duarte (UNCC), Charles W. Martin (University of Florida), Jill A. Olin (Michigan Technological University), Nancy N. Rabalais (Louisiana State University and Louisiana Universities Marine Consortium), Brian J. Roberts (Louisiana Universities Marine Consortium), and Erick Swenson (Louisiana State University)

Main Project Objectives

Examine species composition, relative abundances, and food web structure in natural marshes along a salinity gradient influenced by a river diversion.

Examine species composition, relative abundances, and food web structure across different-aged created marshes that are influenced by a river diversion.

Use the field data gathered above to build and test a food web model (Ecopath with Ecosim) that can be used to predict the impact of habitat restoration on marsh food webs.