ACCESS NUMBER: 30660-19909 

STUDY TITLE: The Development of Bioremediation for Oil Spill Cleanup in Coastal 

Wetlands 

REPORT TITLE: The Development of Bioremediation for Oil Spill Cleanup in Coastal 

Wetlands 

CONTRACT NUMBER: 14-35-0001-30660-19909 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA(S): Central Gulf of Mexico 

FISCAL YEAR(S) OF PROJECT FUNDING: 1994-2000 

COMPLETION DATE OF REPORT: August 2002 

COST(S): FY 1994, $45,863; FY 1995, $45,863; FY 1996, $45,863; FY 1997, $45,863 

FY 1998, $18,695; FY 1999, $24,572; FY 2000, $11,634: CUMULATIVE PROJECT 

COST: $238,353 

PROJECT MANAGERS: Irving A. Mendelssohn 

AFFILIATION: Wetland Biogeochemistry Institute, Louisiana State University 

ADDRESS: Wetland Biogeochemistry Institute, Center for Coastal, Energy and 

Environmental Resources, Louisiana State University, Baton Rouge, LA 70803 

PRINCIPAL INVESTIGATOR(S): I.A. Mendelssohn, Q. Lin, K. Debusschere, C.B. 

Henry, Jr, M.S. Miles, E.B. Overton, R,J, Portier, N.N. Rabalais, P.O. Roberts, and M.M. 

Walsh 

KEY WORDS: Bioremediation, phytoremediation, Oil Spill Cleanup, Coastal Wetlands 

BACKGROUND: The northern Gulf Coast of the United States is a region of intense oil 

exploration, production, transmission, and refining. Consequently, coastal states, such 

as Louisiana, are subject to oil spills resulting from shipping accidents, productionrelated incidents, and pipeline ruptures. Since these incidents often occur in the 

nearshore environment, coastal salt marshes are frequently the first wetland habitat to 

be subjected to the oil. As a result, a large number of investigations have documented 

the effect of petroleum hydrocarbon on the dominant salt marsh species, especially 

Spartina alterniflora. In addition, some investigators have evaluated the impact of oil 

cleanup procedures in salt marshes. Not only can petroleum hydrocarbons have a 

detrimental impact on coastal marshes, but, additionally, the cleanup of the oil from 

these highly sensitive environments is often more damaging than the oil itself. Hence, it 

is important to develop less intrusive oil spill cleanup procedures that exert little to no 

impact to wetland ecosystems. 
ACCESS NUMBER: 30660-19909 

OBJECTIVES: (1) To determine the toxicity and ecological safety of some common 

biodegradation agents. (2) To determine the effect of these bioremediation agents on 

crude oil degradation under the most common marsh inundation environments. (3) To 

determine the effect of biostimulants on crude oil degradation as a function of soil 

texture. (4) To determine the comparative efficacy of bioremediation and 

phytoremediation of oil. 

DESCRIPTION: Although bioremediation of oil spill cleanup has received considerable 

attention in recent years, its satisfactory us in the cleanup of oil spills in the wetland 

environment is still questionable and generally untested. We have conducted a multidisciplinary experimental program to evaluate the use of various bioremediation 

products, including microbial seeding, inorganic fertilizer, and soil oxidant, as a means 

of enhancing oil biodegradation in coastal salt marshes. The program addresses the 

question: Is bioremediation, via fertilization, microbial seeding, or soil oxidant, an 

effective and ecologically safe means of oil spill cleanup in coastal wetlands? 

The effectiveness of bioremediation and its ecological safety were assessed through a 

series of four experiments. The first experiment was designed to determine the toxicity 

and ecological safety of common biodegradation agents. In a greenhouse, the following 

bioremediation treatments were applied to salt marsh sods with intact S. alterniflora: (1) 

fertilizer, (2) microbial seeding, and (3) no bioremediation agent addition (control). The 

experiment used a randomized block arrangement. The second experiment was 

designed to determine the effect of bioremediation agents on oil degradation and biotic 

response under drained and flooded conditions in marsh mesocosms. In the 

greenhouse, the following bioremediation treatments were applied to salt marsh sods 

with intact S. alterniflora: (1) fertilizer, (2) microbial seeding, (3) oxidant plus fertilizer, 

and (4) no bioremediation agent addition (control). Two innundation regimes were 

used, flooded with 3 centimeters of standing water and drained with the water table 10 

centimeters below the soil surface. The third experiment compared the three major 

categories of bioremediation agents, fertilizer, microbial seeding, and soil oxidant, as a 

means of enhancing oil biodegradation in coastal mineral and sandy marsh substrates 

under controlled greenhouse conditions. The fourth experiment compared the effects of 

phytoremediation and bioremediation on oil degradation. In the greenhouse, the 

following treatments were applied to the experimental units: (1) phytoremediation with 

S. alterniflora or without, (2) three nitrogen levels, and (3) two phosphorus levels. 

SIGNIFICANT CONCLUSIONS: Bioremediation by adding non-bacterial agents to 

enhance natural oil degradation has considerable potential in wetland environments. 

Application of fertilizer, either in the form of slow release or water soluble, significantly 

enhanced plant growth with significantly higher photosynthetic rates, stem growth rates, 

and above- and below-ground biomass of S. alterniflora. In addition, application of 

fertilizer significantly reduced the concentrations of both the reduced crude oil and the 

artificially weathered crude oil. In the absence of S. alterniflora, however, 

bioremediation by nitrogen and/or phosphorus addition did not significantly affect 
ACCESS NUMBER: 30660-19909 

residual oil concentration. These results suggest that oil biodegradation in marsh 

systems may be enhanced by fertilization (biostimulation). 

STUDY RESULTS: Efficacy and success of bioremediation of oil to accelerate the 

biodegradation process depend on the extent of contaminant removal and on the 

ecological safety of the bioremediation agents. The bioremediation agents used in this 

research, including a microbial product and inorganic fertilizers, had no negative 

impacts to the plant, animal, and microbial responses evaluated in this study. 

Application of the bioremediation agents at the specified application rates to the salt 

marsh sods did not adversely affect the marsh macrophyte, S. alterniflora, various 

microbial populations and soil respiration, and various infaunal animals including 

macrofauna and meiofauna. Application of fertilizer, either in the form of slow release or 

water soluble, significantly enhanced plant growth with significantly higher 

photosynthetic rates, stem growth rates, and above- and below-ground biomass of S.

alterniflora. The fertlizer-enhanced oil degradation occurred only in the presence of the 

marsh macrophyte, S. alterniflora. The effect of fertilization on oil degradation by 

directly enhancing soil microbial activity was separated from the phytoremediation effect 

by comparing bioremediation by added nitrogen and phosphorus in the absence of 

plans with that in the presence of S. alterniflora. Application of the soil oxidant did not 

significantly affect oil degradation in the marsh sods. The microbial product did not 

significantly affect oil degradation. This study suggests that the high cost of microbial 

amendments and soil oxidant application for oil bioremediation may not be warranted in 

coastal marshes. 

STUDY PRODUCTS(S): Mendelssohn, I.A. (ed.). 2002. The development of 

bioremediation for oil spill cleanup in coastal wetlands. OCS Study MMS 2002-048. 

U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico Region, New 

Orleans, LA, 98 pp.