by Mahlon C. Kennicutt
Many uncertainties surround the importance of environmental disturbances caused by offshore oil and gas development and production. The most significant unanswered questions involve chronic, low-level stresses on ecosystems which result from discharges, spills, and leaks associated with the long-term development of energy resources on the continental shelf. A multidisciplinary team of researchers at Texas A&M University (TAMU) and other institutions is conducting a three-phase program, called the Gulf of Mexico Offshore Operations Monitoring Experiment (GOOMEX), to test and evaluate a range of biological, biochemical, and chemical methods that may indicate whether or not the local ecology around platforms is responding to chronic, sublethal exposure to discharged pollutants.
[94K] [85K] Kristie Willett, a graduate student in Veterinary Physiology and Pharmacology at Texas A&M University, conducts experiments to determine how fish have responded to exposure to organic contaminants associated with oil and gas platforms in the Gulf of Mexico.
Offshore petroleum platforms are known to discharge a range of materials over their lifetimes. These discharges can be associated with activities such as drilling, ship operations, accidental spills, run-off from the platform, discharge of produced waters, sand blasting, painting, welding, and other practices. As a structure, a platform can also act as a reef and produce a flux of materials to the seabed from biological organisms attached to the platform and inhabiting the surrounding waters. As a result of these various inputs our team of investigators expected that the presence of a platform over a number of years would lead to a significant alteration of the underlying seafloor and the organisms that live there. We also expected that this change would directly or indirectly alter the local ecology.
Conditions around platforms result from the cumulative long-term interaction between the platform structure, materials discharged from the structure, and local oceanographic conditions. In the simplest sense, the three-year Phase I of GOOMEX aimed to develop a detailed understanding of whether or not conditions measured near a platform are significantly different from those away from the platform, and whether or not these differences could be attributed to the discharge of pollutants from the structure. Specifically, the program was designed to test for toxic responses to contaminants, but it also assessed alteration of seafloor sediment characteristics around platforms. Disposal of coarse materials onto the surrounding sediments sets the stage for a shift in marine-organism populations. Thus, aside from toxicity caused by contaminants, we expected alteration of the seafloor (i.e., a change in sediment grain size) and organic enrichment derived from marine organisms living on the platform to exert significant additional controls over biological patterns.
Changes in variables related to distance from the platform can only be fully understood within the concepts of cause and effect and biological significance. Any two places on the continental shelf can be determined to be different if analyzed in sufficient detail. The GOOMEX program is designed to provide circumstantial evidence of cause and effect at several levels of biological organization as well as provide a foundation for future studies of the processes through which the changes take place.
To increase confidence in our interpretations, we compared the indications of ecological impact across several independent lines of evidence and evaluated how well they agreed with one another. We also used the concept of biological significance as a guiding principle. The goal of monitoring is to detect resource degradation or environmental damage and then provide guidance for prevention or reversal of undesirable impacts. The relevance of specific effects must interpreted in the broader context of the insults being sustained by marine resources in general.
The two most likely types of toxic contaminants associated with platforms are petroleum hydrocarbons and metals (iron, lead, cadmium, zinc, etc.). The distributions of each contaminant can serve as an indicator of the potential for toxic effects. To implement Phase I of the program our team of investigators analyzed metal and hydrocarbon contaminants in bulk sediments, the water contained in them, and the tissues of marine organisms. We also examined three different size ranges of bottom-dwelling marine invertebrates (meio, macro, and megafauna) in terms of their community structure, life histories and reproductive effort. Finally, we assessed the presence and intensity of biochemical systems that protect animals from contaminants. The program involved intensive sampling of the study sites (four sampling events over 1 1/2 years) and state-of-the-art analytical techniques to produce a comprehensive data set to test our hypotheses.
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Oceanography, Texas A&M University
Updated September 13, 1995