Dynamic Solutions

Myrtle Grove Ecological Modeling

The medium diversion at Myrtle Grove (MDMG) ecosystem restoration project involves diverting freshwater from the Mississippi River into Barataria Basin near Myrtle Grove, Louisiana. The sediment-rich river water flowing into Barataria Basin has potential for land building and marsh restoration, but not without altering current environmental conditions in the area. The Comprehensive Aquatic Systems Model (CASM) will be used to assess the potential effects of changing environmental conditions for future-without and future-with-project diversion operation scenarios on the distribution and production of important fish and invertebrate populations in Barataria Basin.

The CASM is a flexible mass-balance aquatic food web modeling platform that has been used for a variety of freshwater and coastal aquatic ecosystems. A version of the CASM was developed for the Mississippi River Gulf Outlet (MRGO) ecosystem restoration study to evaluate ecological responses to the proposed river diversion. The CASM MRGO will be adapted for the Barataria Basin ecosystem in order to evaluate potential ecological responses to the proposed MDMG. The food web processes and population parameters of the component fish and invertebrate species will be verified and updated from available field and long-term monitoring data collected by the Louisiana Department of Wildlife and Fisheries (LDWF) within the system.

The CASM MDMG will be a series of the food web models set up at selected locations throughout Barataria Basin. The food web model will focus on key species of ecological, recreational, and commercial value, including eastern oysters, brown shrimp, white shrimp, blue crab, red drum, spotted seatrout, striped mullet, Gulf menhaden, Atlantic croaker, largemouth bass, blue catfish, and bay anchovy. The daily population growth of species in the CASM is determined by bioenergetics-based equations, and daily environmental conditions at the selected locations differentially modify maximum photosynthesis (for phytoplankton and vegetation) and consumption rates of the species within the food web. CASM locations will use model output and available station data for nutrient concentrations, organic matter, and suspended sediments from the US Geological Survey and Coastwide Reference Monitoring System monitoring programs and a water quality study performed by the US Army Corps of Engineers.

The CASM MDMG will be run for the 50-year project life under baseline conditions for selected years, and then run for each of the alternative diversion operation scenarios.

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