The Deepwater Horizon (DWH) oil spill exposed the nation's largest and most productive wetlandestuarine environment, the Mississippi River Delta coastal wetland ecosystem, to an unprecedented potential for environmental damage. The coastal marshes are of special concern because of the suite of environmentally and economically important services they support, all of which depend on a healthy, well-functioning plant-microbial-benthic complex that drives the food web base. Over the last five years, the PI’s team has monitored DWH oil spill effects in Louisiana, making 12 field-based data collections that have quantified both the impacts on, and recovery of, a broad array of flora and fauna. Continuing this research is especially important along heavy oiled shorelines where the marsh plants that serve as foundation species suffered severe mortality. Results to date indicate that recovery is occurring but not yet complete. Hence, a much longer-term study is needed to fully quantify the recovery of the plantmicrobial- benthic complex and to better understand marsh resiliency. Furthermore, the PI’s team has initiated, and is currently monitoring a remediation/restoration effort that could accelerate the recovery rate of lost ecological services. Therefore, the overall goals of this proposed research are to (1) document the long-term impacts of the DWH oil spill on the coastal marsh plant-microbial-benthic complex, (2) quantify rates of, and controls on, long-term recovery, and (3) evaluate the potential and effectiveness of a restoration and remediation strategy for promoting and accelerating long-term sustainability. This proposed research supports GoMRI theme 3: (1) knowledge of environmental effects of petroleum on wetlands, marshes and organisms and (2) the science of ecosystem recovery and means for accelerating recovery.
Oil spills can cause widespread impacts to the structure, function, resilience and sustainability of coastal wetlands. Previous and ongoing GoMRI funded research by the PI’s team has identified several of these impacts resulting from the Macondo oil spilled in Louisiana’s coastal wetlands, as well as subsequent recovery. The pattern of effects and recovery documented have resulted, in large part, from differences in oiling intensity and species-specific responses. For example, in moderately oil marshes, Spartina alterniflora recovered within 9 months post spill while Juncus roemerianus did not recover until ~3 years post spill. Benthic microalgae, invertebrates, and soil microbes were also affected but recovered concurrently with the vegetation. Heavy oiling, in contrast, almost completely killed the marsh vegetation, greatly reduced benthic microalgae and fauna, and decreased overall bacterial populations. To date, Juncus has not recovered along heavily oiled shores, and the vegetation structure has shifted from a Juncus-Spartina community to mostly Spartina. These changes in ecological structure have greatly reduced marsh productivity, slowed the recovery of microbes and some invertebrates, and increased the potential for erosion. In particular, soil shear strength in heavily oiled sites has consistently been lower than at reference sites, making these areas more vulnerable to deterioration, which further threatens wetland sustainability. In April 2014, restoration plantings and remediation with nutrient stimulation were initiated and continue to be evaluated for long-term effectiveness. An initial evaluation of this planting/nutrient amendment experiment indicates promising results towards accelerating the pace of recovery and enhancing marsh sustainability. In addition, the PI’s team proposes two more manipulative field experiments designed to better understand linkages and interactions within the plant-microbebenthic complex, leading to improved remediation strategies associated with replanting.
The PI’s team research experience on oil impacts and remediation, in general, and the DWH spill specifically, is highly qualify to conduct the proposed research. Collectively, this group has published more than 50 refereed scientific papers on oil spill science, with 4 publications and 3 manuscripts in review on the DWH spill. In addition, the 54-month database on DWH oiling impacts and recovery generated to date provides valuable information to assess long-term natural and vegetation-assisted recovery and sustainability. The proposed research will emphasize ecological assessments of plant structure and function, interactions within the plant-microbe-benthic complex, cultivation-based and modern molecular biological analysis of microbial communities, algal and invertebrate responses, biogeochemistry, digital aerial imagery for erosion assessment, and overall marsh integrity. This research will provide a better scientific understanding of the oil spill effects and long-term recovery of the plantmicrobial- benthic ecosystem, as well as practical information concerning strategies for accelerating ecosystem recovery, and thus long-term sustainability, of oil impacted coastal wetlands.
Project Research Overview (2016):
An overview of the proposed research activities from the GoMRI 2016 Meeting in Tampa.
Direct link to the Research Overview presentation.