An estimated 4.9 million barrels of oil from the Deepwater Horizon (DWH) blowout have affected the nation’s largest and most productive wetland-estuarine environment. Healthy plant-soil-benthic communities are vital to sustaining marsh structure and function and to promote important wetland services. Although the immediate short-term impacts of the DWH oil spill on coastal wetland vegetation are obvious, the long-term ecological impacts and recovery from this oil spill are virtually unknown.
Our on-going one-year research project (LSU-GRI phase 1) is investigating the effects of the DWH oil spill on the ecological response of wetland vegetation and soil biogeochemistry with the goal of assessing short-term impacts and initial recovery that may occur immediately after the spill. However, clearly oil impacts and recovery in wetlands may take years, and delayed impacts and cascading effects on benthic biota may yet occur and need to be determined. Accordingly, we propose continuation of our phase 1 study, and expansion of our research to include impacts on infaunal invertebrates and benthic microalgae as well as another marsh type (Juncus roemerianus). Inclusion of these important consumers and producers will greatly contribute to a more comprehensive investigation of the effects of the DWHoil spill on structure and function of coastal wetlands.
Given the preceding background, the primary goal of the proposed research is to further our knowledge of the long-term effects of the DWH oil spill on the ecology of coastal wetlands and their capacity for recovery. Special emphasis will be placed on marshes dominated by the plant species Spartina alterniflora and Juncus roemerianus. Our field observations indicate that oil-impacts varied greatly for these two species - little recovery of Juncus but considerable recovery of Spartina in most locations. These greatly different effects in the short-term will most likely lead to different long-term impacts with consequences for benthic biota and overall recovery.
We shall use both field and greenhouse approaches to accomplish our research goal. We shall employ field sites in northern Barataria Bay, where Spartina and Juncus co-occur. Replicated field plots that have received heavy, moderate and no oiling will be sampled to assess the long-term oil impacts and recovery of coastal salt marshes. Greenhouse treatments, which use natural marsh sods of the two species (Spartina and Juncus) and the DWH source oil, will include different degrees of oil coverage of the vegetation and soil to determine whether effects on structure and function of marshes differ with wetland type and what factors control any differential response.
We shall assess long-term impacts to and recovery of (a) marsh plant structure and function, (b) soil physico-chemistry, (c) benthic microalgae structure and function, (d) infaunal invertebrate structure and function, and (5) marsh integrity. The proposed research directly addresses the LSU-GRI’s priority area of understanding the fate of the oil, its biological and ecological impact and recovery of natural resources. The results derived from the proposed project will be important from both a basic scientific standpoint and as applied research. The integration of macrophyte, microalgae and infauna responses will further promote our understanding of their relationship and how perturbations, such as oil spills, regulate their interaction.
The research will provide the important value of assessing the long-term impacts of the DWH oil and recovery of different marsh types, which could benefit restoration of oil-impacted wetlands. Our extensive oil spill-related research in wetlands has already attracted considerable news media and public attention regarding the DWH oil spill as well as educational opportunities. In addition, the research will greatly improve our ability to acquire external funding for long-term investigations of oil impacts and recovery from the DWH oil spill beyond the duration of the project.