RAPID: Community-level Wetland Stressors, Northern Gulf of Mexico

Louisiana State University, Baton Rouge LA

Investigators

Abstract

This project addresses scientific questions about changes in the biological community of Louisiana salt marshes caused by the Deepwater Horizon oil spill in the Gulf of Mexico. A team of experienced investigators will sample 35+ salt marshes in September 2010 and May 2011, adding to the samples already collected from these sites in May 2010. Thus, the sampling will cover the periods before the marshes are oiled, at the peak of the growing season, and one year later. Data will be collected on the biomass of the dominant aquatic plant (cordgrass, Spartina alterniflora), soil metabolism, changes in sulfur accumulation, stable isotope signatures, nitrogen fixation rate, and the parasitic and symbiotic invertebrate community. The data collected will be used to test various hypotheses about the effects of chronic and long-term stressors (oil, toxins, dispersants, or nutrients) on salt marsh ecosystems, including predictions about indirect long-term consequences to the salt-marsh community. This exceptionally large oil spill event provides an unusual opportunity to learn about the short- and long-term stressors on ecosystems, but only if there are sufficiently large and varied baseline measurements. Environmental stressors such as those arising from hydrocarbon spills, can have visible and immediate direct impacts on coastal ecosystems due to physical and toxic effects on organisms. Stressors also have indirect effects because, as they begin to degrade, the compounds enter food webs via primary consumers such as suspension-feeding oysters, deposit-feeding bivalves, and grazing snails. These consumers, in turn, are food sources for organisms at higher trophic levels, including humans. The effects of a major environmental stressor can, therefore, cascade through the community as members of lower trophic levels undergo changes in growth, mortality, and reproductive success, and as species turnover occurs and metabolic pathways are altered. The project goals are to provide a benchmark study in marsh ecosystem change, and to predict alternative states in time for compensatory management actions.