The biogeochemical impacts of oil spill on elemental cycling in coastal ecosystems
Henry Wan (PI), Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University; Qiang
He (Co-PI), Department of Environmental Engineering, University of Tennessee, Knoxville
Background: Microbial transformations are key determinants of biogeochemical processes supporting the vast but
vulnerable coastal ecosystems along the Gulf of Mexico. The availability, distribution, and transport of many
important elements, including both macro- and micro-nutrients as well as ones that are harmful, are critically
influenced by redox-dependent transformations catalyzed by microorganisms. It is well known that microbial
populations form cascading trophic groups along the redox gradient in sediment environments, participating in the
global cycling of elements including C, N, S, Fe and other trace metals, via microbial electron-accepting processes.
Recently, increasing evidence has shown that viral activities are another important process controlling microbial
abundance, particularly in perturbed environments where the equilibrium of the existing microbial community is
drastically disrupted. The Gulf oil spill from April 20 to of Sep 19 of 2010 represents an unprecedented perturbation to
the Gulf coastal ecosystems that will undoubtedly alter the microbial community in impacted coastal areas and
subsequently influence elemental cycling. Monitoring and understanding these impacts will gain insight into the key
processes disturbed by the oil spill and provide guidance to the rational design of effective restoration strategies and
processes for oil impacted coastal ecosystems.
Hypothesis and goal: The Central Hypothesis for this project is that the exposure of ecologically vulnerable
coastal ecosystems to crude oil as an extraneous source of carbon and an added barrier for air/liquid mass transfer
would result in significant changes in the trophic cascades and functions of the microbial communities that would
negatively impact the biogeochemical cycling of elements, which are critical to the health of the entire coastal
ecosystem in the Mississippi Delta. With the overall goal to monitor and understand the biogeochemical processes
impacted by the oil spill in order to design effective strategies and processes for ecosystem restoration, the objective
of this proposed study is to monitor the dynamics of the structure and functions of the microbial communities in the
coastal mashland/wetland areas with increasing levels of exposure to crude oil as a persistent stress. The focus of
this study will be the impacts of oil spill on sediment microbial populations involved in elemental cycling, such as
carbon mineralization, nutrient transport, and metal mobilization, processes paramount to the proper functioning of
the impacted ecosystems. The specific aims from this study include:
AIM 1. Sample collection in contaminated sites. Monthly water samples and sediment core samples will be taken
from both contaminated and uncontaminated coastal sites in the Mississippi Delta. Care would be taken to
select sites with maximum similarity but the presence of crude oil. The extent of oil contamination will be
classified by the coverage of the sediment surface. The comparisons between contaminated and
uncontaminated samples will provide information on the individual processes responsive to the presence of oil.
Ecological and geographical data related to the sampling sites will also be collected.
AIM 2. Characterization of the composition and structure of sediment microbial communities. Both DNA and
RNA samples will be extracted from the sediment samples collected in AIM 1 so that we can identify microbial
as well as viral populations in these samples using metagenomic and metatranscritompic analysis through
Solexa or 454.
AIM 3. Characterization of the function of sediment microbial communities. The basic physical and chemical
data will be characterized for sediment samples. Multivariate statistical analysis and GenGis will be used to
integrate the phylogenetic sequence information with ecological and geographic data for understanding the
function of sediment microbial communities and their correlations with presence and absence of oil
contaminations.
Proposed budget and justification: We would like to budget $142,782 for Phase II, including $30,000 for microbial
extraction, RNA purification, and pyrosequencing, $3,000 for field sample collection, and a graduate student for 12
month support, and $30,000 subcontact for water ultrafiltration and chemical characterization.