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STUDY TITLE: Planning Workshops for Oil Spill Remediation for Habitats and 

Resources in the Gulf of Mexico 

REPORT TITLE: Symposium Proceedings: Gulf of Mexico and Caribbean Oil Spills in 

Coastal Ecosystems: Assessing Effects, Natural Recovery, and Progress in 

Remediation Research -- New Orleans, July 14-15, 1994 

CONTRACT NUMBER: 14-35-0001-30690 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA: Gulf of Mexico 

FISCAL YEARS OF PROJECT FUNDING: FY 92-98 

COMPLETION DATE OF REPORT: June 1996 

CUMULATIVE PROJECT COST: $225,000 

PROJECT MANAGER: E. Proffitt 

AFFILIATION: McNeese State University, Louisiana Environmental Research Center 

ADDRESS: P.O. Box 90655, Lake Charles, Louisiana, 70609-0655 

PRINCIPAL INVESTIGATOR: E. Proffitt 

KEY WORDS: Mangrove Ecosystems, Oil-Spill Impacts, Remediation, Restoration 

BACKGROUND: This technical report on oil in mangrove ecosystems contains papers 

written by participants of a Workshop held August 1995 at McNeese State University 

and sponsored by the U.S. Minerals Management Service. It is the second in a series 

of three workshops which were supported under a cooperative agreement between 

MMS and McNeese State University. In the mangrove technical report experts with a 

variety of professional backgrounds address subjects including the effects of oil and 

modeling these effects, restoration of oiled habitat, solutions for remediating oil impacts. 

OBJECTIVES: The technical report: (1) reviews the states-of-knowledge on oil spill 

impacts and discusses a possible model; (2) evaluates management practices of 

remediation and habitat restoration; and (3) identifies areas where future research is 

critically needed. 

DESCRIPTION: The magnitude and spatial location of emergent coastal vegetation 

(including salt and brackish marshes and mangrove forests) in the Gulf of Mexico 

exceeds 6 million acres. Of this, 64% occurs in Louisiana and 19% in Texas. Welldeveloped mangrove forests dominate the low-wave-energy intertidal shoreline from 
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about mid peninsular Florida south through the Florida Keys. Numerous mangrove 

forests have been subjected to perturbation by oil spills in various parts of the world 

and this workshop was undertaken to address problems in terms of what is truly 

"known" (versus what is "asserted" from casual observations) of the effects of petroleum 

and remediation of these effects. 

SIGNIFICANT CONCLUSIONS: Oil causes mortality and reduced growth of the 

dominant plant species in both marsh and mangrove habitats. However, there is wide 

variation in the degrees of "effects" that depends on: (1) the type and degree of 

"weathering" of oil spilled, (2) the plant species affected, (3) the frequency of spills, (4) 

the possible synergistic influences of other stressors such as high salinity or freezes, (5) 

local conditions (e.g., point in the tidal cycle, levels of rainfall and co-occurrence of 

storms and oil spills) and (6) effects of other biota (e.g., fiddler crab burrows can 

facilitate penetration of oil into the sediment). 

Oil produces mutations in mangroves and probably (but this has not yet been studied) in 

marsh plant species. The rate of mutations in the genes that produce chloroplasts was 

directly, linearly, proportional to the soil concentration of polynuclear aromatic 

hydrocarbons (PAHs) derived from petroleum. These findings suggest to important 

possibilities. 

Oil causes extensive mortality in invertebrate populations, probably affects fish that 

forage in the systems at high tide, and almost certainly disrupts many important 

ecological processes that they mediate in mangrove systems. These links have 

received little attention and an assessment of the effects of oil on ecological processes 

needs to be a research priority. 

Oil soaks into mangrove sediments and probably affects soil microbial assemblages 

that are fundamental to detrital decay and re-mineralization of nutrients. These poorlystudied communities also fuel major food webs of the marsh and mangrove systems 

and the adjacent open water portions of the estuaries. Understanding the effects of oil 

contamination on marsh and mangrove sediment microflora is critical to truly 

understanding the long-term consequences of oil in these systems. 

Oil may affect the outcomes of ecological succession through differential effects on 

marsh and mangrove species. Differential mortality or reductions in growth rates and 

reproductive fitness may have long-term consequences on community structure by 

changing competitive dominance and succession patterns. Few studies have 

addressed this problem and thus this is an area of needed research. 

STUDY RESULTS: Bioremediation has been a topic of considerable management and 

research interest for some time. There are two fundamental ways that bioremediation 

(using microbes to degrade oil) is carried out. First, nutrients can be used in aerobic 

environments to stimulate growth of naturally-occurring microbial species that consume 

petroleum hydrocarbons. Second, laboratory cultures of bacteria and/or 

bacteria+nutrient amendments can be applied to sites that have been oiled. 
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Positive results (oil degradation) that may occur in lab experiments with such cultures 

rarely, if ever, are particularly effective in the field. However, this is an area for further 

research. 

Remediation burning of oil is another mechanism that has been applied in a few 

instances in marshes. Burning has not been attempted as a oil spill management 

technique in mangrove forests and workshop participants believed that its use would 

probably be inappropriate in this system. 

Oil dispersants and vegetation cleaners have received use in both real spill and 

experimental settings and a number of problems with use of these chemicals has been 

noted. Most notably, the toxicity of dispersed oil to most species is unclear. 

Flushing oil using water under pressure and vacuuming oil holds promise for removing 

ponded oil from marsh and mangrove systems and should be evaluated further. Low 

pressure flushing with un-heated water may be an effective way to remove pooled oil 

without disrupting the sediment of the marsh or mangrove system. 

Sorbents (materials that absorb oil) occur in a variety of types and have been used to 

blot oil from marsh or vegetation surfaces. Many of the most promising are "natural" 

materials such as matted, dried vegetation that may absorb and hold oil (therefore 

keeping it out of marsh or mangrove sediments) and maintain it in an aerated 

environment to increase microbial degradation of the oil. 

Habitat restoration will be important after many oil spills. In some instances natural 

recovery of a remediated and "prepared" site may be all that is necessary. However, in 

many instances planting mangroves will greatly enhance the rate of initial mangrove 

cover and eventual forest development and succession. 

STUDY PRODUCTS: Louisiana Environmental Research Center McNeese State 

University 1997. Managing Oil Spills in Mangrove Ecosystems: Effects, Remediation, 

Restoration, and Modeling. A final report for the U.S. Department of the Interior, 

Minerals Management Service Gulf of Mexico OCS Region, Metairie, LA. NTIS No. 

PB98-142268. Contract No. 14-35-0001-30690. MMS 97-0003. 81 pp. 

Louisiana Environmental Research Center McNeese State University 1997. Effects and 

Management of Oil Spills in Marsh Ecosystems, A Review Produced from a Workshop 

Convened Jul 1996 at McNeese State University. A final report for the U.S. Department 

of the Interior, Minerals Management Service Gulf of Mexico OCS Region, Metairie, LA. 

NTIS No. PB98-141427. Contract No. 14-35-0001-30690. MMS 98-0018. 45 pp. 

Louisiana Environmental Research Center McNeese State University 1997. 

Symposium Proceedings: Gulf of Mexico and Caribbean Oil Spills in Coastal 

Ecosystems: Assessing Effects, Natural Recovery, and Progress in Remediation 

Research. A final report for the U.S. Department of the Interior, Minerals Management 
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Service Gulf of Mexico OCS Region, Metairie, LA. NTIS No. PB96-185764. Contract 

No. 14-35-0001-30690. MMS 95-0063. 249 pp.