ACCESS NUMBER: 30660-19927 

STUDY TITLE: Potential for Accelerated Bioremediation and Restoration of OilImpacted Marshes Through the Selection of Superior Oil-Tolerant Vegetation 

REPORT TITLE: Potential for Accelerated Bioremediation and Restoration of OilImpacted Marshes Through the Selection of Superior Oil-Tolerant Vegetation 

CONTRACT NUMBER: 14-35-0001-30660-19927 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREAS: Gulf and Atlantic coast marshes 

FISCAL YEAR(S) OF PROJECT FUNDING: 1995; 1996 

COMPLETION DATE OF REPORT: May 2000 

COST(S): FY 1995: $46,863; FY 1996: $45,212; CUMULATIVE PROJECT COST: 

$92,081 

PROJECT MANAGER: Mark W. Hester 

AFFILIATION: Southeastern Louisiana University 

ADDRESS: Department of Biological Sciences, Hammond, LA 70402 

PRINCIPAL INVESTIGATORS*: Mark W. Hester, Irving A. Mendelssohn 

KEY WORDS: Gulf of Mexico, oil spill, brackish marsh, salt marsh, Spartina patens, 

Spartina alterniflora, growth, photosynthesis, bioremediation, phytoremediation, 

petroleum hydrocarbons, wetland rehabilitation 

BACKGROUND: The cleanup of oil spills in coastal marshes remains a problematic 

issue because wetlands can be extremely sensitive to the disturbances associated with 

cleanup activities. As a result, there has been interest in developing alternative, less 

intrusive, oil spill cleanup/bioremediation techniques. The research reported herein 

assessed the feasibility of identifying superior oil-tolerant genotypes of Spartina patens

and Spartina alterniflora (dominant brackish and salt marsh grasses, respectively) that 

may be utilized in the restoration and bioremediation of oil-impacted marshes, as well 

as in the rehabilitation of marshes in areas with a high amount of oil activity. 

OBJECTIVES: To specifically addresses whether superior oil-tolerant populations of 

Spartina patens and Spartina alterniflora (dominant Gulf Coast brackish and salt marsh 

grasses) can be identified that display 1) superior growth response and plant production 

under oil stress, 2) superior vegetative regrowth through oiled soil, and 3) superior oil 

degradation potential. 
ACCESS NUMBER: 30660-19927 

DESCRIPTION: Transplants of Spartina patens and Spartina alterniflora were collected 

from Gulf Coast populations in Louisiana, Texas, and Florida. Each population was 

then propagated from a single stem (individual) to ensure that each population was 

represented by a single genotype. Ten different genotypes were propagated for each 

species. The oil tolerance experiments were run sequentially over a two-year period 

utilizing similar experimental protocols. 

The ten different genotypes of each species were established in a uniform potting mix of 

approximately 10% organic matter content by weight. The soil of the treatment pots 

was oiled with South Louisiana crude oil at rates known to be stressful from previous 

research (5 L oil m-2 for S. patens and 8 L oil m-2 for S. alterniflora). The oil was applied 

directly to the surface flood water of the treatment pots and allowed to slowly drain 

through the soil column over a period of about two hours. Drainage was stopped just 

prior to the drainage of any oil, thereby ensuring even oiling of the substrate without loss 

of oil. For each pot, the drain water was collected in a reservoir bucket and 

subsequently slowly returned to the top of the treatment pot soil. The control pots 

received no oil, but were similarly drained and had the solution returned to the surface 

of the pots. Throughout the study, water levels were maintained at the level of the soil 

surface. Measurements of plant growth and physiological responses were conducted 

during the growing season, after which an initial harvest of aboveground biomass was 

conducted. Vegetative regrowth through the oiled soil was monitored for an additional 

three months, after which a final harvest was conducted and residual oil in the soil 

determined.

SIGNIFICANT CONCLUSIONS: In both Spartina patens (brackish marsh dominant) 

and Spartina alterniflora (salt marsh dominant), significant intraspecific variation to oiling 

was observed in a number of plant responses. Of the ten genotypes assessed in each 

species, several genotypes in each species could be identified that displayed superior 

oil tolerance in terms of single and multiple plant-growth responses to oiling. This 

finding has important ecological and applied value. Oil-tolerant genotypes of these 

species may be planted in marsh rehabilitation (restoration and creation) projects in 

areas of high oil activity, thereby potentially increasing the resiliency of these marshes 

to oiling, should an oil spill occur. Of the three oil-tolerant genotypes of Spartina patens

identified, two of these genotypes also displayed the potential for accelerating the 

degradation of oil, thereby indicating the potential for enhanced rates of bioremediation 

(phytoremediation). 

STUDY RESULTS: Highly significant genotype differences in a number of plant 

responses were detected in both species when oiled. Differences between genotypes 

generally became more pronounced with time, with the exception of leaf expansion rate, 

which proved to be a less sensitive short-term indicator of oil stress than photosynthesis 

(net CO2 assimilation rate). Three genotypes of Spartina patens and three genotypes of 

Spartina alterniflora were identified that maintained high rates of photosynthesis when 

oiled and also generally performed better than the other genotypes in terms of a number 

of plant growth response variables, including regrowth through the oiled soil. Univariate 

statistical analyses were unable to detect any significant differences between genotypes 
ACCESS NUMBER: 30660-19927 

in oil degradation rates in either species, although multivariate techniques did detect 

genotype differences in Spartina patens. 

A multivariate analysis (factor analysis) that was conducted on a suite of plant growth 

response variables and residual oil confirmed that three superior, oil-tolerant genotypes 

could be identified in each species (both Spartina patens and Spartina alterniflora) that 

performed significantly better than the other genotypes. When oiled, these oil-tolerant 

genotypes characteristically displayed less tissue death, maintained higher plant 

productivity, and demonstrated a greater ability to successfully produce new shoots 

through the oiled soil. Analysis of oil-degradation factor scores in S. patens further 

revealed that two of the three oil-tolerant genotypes demonstrated significantly greater 

oil-degradation potential than other genotypes. For both species, it is likely that in the 

long term (and under field conditions), greater rates of oil degradation would be 

associated with those genotypes that display less stress and greater plant productivity. 

STUDY PRODUCT(S): M. W. Hester, Q. Lin, I. A. Mendelssohn, and D. J. Desroches. 

1998. Potential for accelerated bioremediation and restoration of oil-impacted marshes 

through the selection of superior oil-tolerant vegetation. A final report by Southeastern 

Louisiana University and Louisiana State University for the U.S. Department of the 

Interior, Minerals Management Service Gulf of Mexico OCS Region, New Orleans, LA. 

Contract No. 14-35-0001-30660-19927 OCS Study MMS 2000-042 62 pp

*P.I.’s affiliation may be different than that listed for Project Manager(s).