The Macondo 252 oil spill resulting from the blowout of the Deepwater Horizon drilling platform on April 20, 2010 is debatably the largest environmental disaster ever experienced in the United States, and, without question, the largest oil spill. The release of an estimated 4.9 million barrels of oil exposed the nation's largest and most productive wetland-estuarine environment to an unprecedented potential for environmental damage.
The Mississippi River delta coastal wetland system, which comprises almost 40% of all coastal wetlands of the 48 conterminous United States, is of special concern because of the suite of environmentally and economically important services they provide, not only to the northern Gulf of Mexico, but also to the nation. Most, if not all, of these ecosystem services are dependent on a healthy, functioning soil-microbial-plant system, which provides the base for such ecosystem services such as hurricane and storm protection, water quality enhancement, faunal support, sedimentation and carbon sequestration, and many others. Hence, the critical importance of understanding to what extent the soil-microbial-plant system and dependent ecosystem services have been impacted by the Macondo 252 oil spill is evident.
Our proposed research will address the question: Did the Macondo 252 Oil Spill cause large-scale perturbations to the structure and function of soil-microbial-plant ecosystems in the wetlands of the northern Gulf of Mexico?
Specifically, we shall answer the following questions:
1. What are the effects of the spilled oil on the ecological structure and function of the soil-microbial-plant system of coastal salt marshes dominated by Spartina alterniflora and Juncus roemerianus?
2. How do these effects on microbial and plant structure and function differ with dominant plant species (Spartina or Juncus) and what factors determine any differential response?
3. What is the relative sensitivity of dominant plant species to different degrees of oiling and how does mode of oil-exposure (above ground versus below ground) control response?
The proposed research will combine field studies and greenhouse-mesocosm experiments, the latter employing field-collected vegetated soil-sods. We shall assess impacts to and recovery of:
1. Microbial structure and function
2. Marsh vegetation structure and function
3. Soil physico-chemistry
High-throughput functional gene microarray (GeoChip) analysis and gene-specific clone library for microbial samples and soil biogeochemical techniques and plant ecological assessments of structure and function will be emphasized. The integration of the plant and the microbial systems within the same experimental design will allow direct comparisons of response to oil. The proposed research directly addresses NGI themes 1 (Ecosystem Based Management) and 4 (Coastal Hazards and Resiliency).
The information resulting from the proposed research has intrinsic value in addressing relationships between the soil microbial community and vegetation structure and function and how disturbances, such as oil, mediate these relationships. From an applied perspective, the research will determine ecological impact to microbial and vegetation systems immediately after the spill so that restoration can proceed with specific microbial and ecological endpoints as targets from which restoration success can be evaluated.