Effects of a used drilling fluid on an experimental seagrass community (Thalassia testudinum Konig et Sims) were measured by exposing the community to the suspended particulate phase (SPP) in laboratory microcosms. Structure of the macroinvertebrate assemblage, growth and chlorophyll content of grass and associated epiphytes, and rates of decomposition as indicated by weight loss of grass leaves in treated and untreated microcosms were compared. Health of the plants and structure of the macroinvertebrate assemblage maintained in the laboratory were compared periodically with the seagrass community from which the plants and attendant sediment were taken.
Treated microcosms were exposed to either 190 parts per million (ppm), volume to volume, of SPP or an equivalent amount of montmorillonite clay. Untreated microcosms received only flowing water from Santa Rosa Sound. Sixteen replicates were provided for each treated and untreated set.
There were statistically significant differences in community structure and function among untreated microcosms and those receiving the clay and drilling fluid. For example, drilling fluid and clay caused a significant decrease in the numbers of the ten most numerically abundant (dominant) macroinvertebrates, and drilling fluid decreased the rate at which Thalassia leaves decomposed.
Following the Valdez spill in Alaska in 1989, Exxon scientists worked closely with the U. S. Environmental Protection Agency (EPA) and the State of Alaska, to conduct the most extensive bioremediation study on oiled shoreline ever carried out. Over $10 million was spent conducting this research. The process involved applying fertilizers on intertidal shorelines to stimulate the growth of indigenous oil-degrading microbes and accelerate the rate of natural degradation of the oil. In analyzing the data from this program, Exxon developed unique approaches, focusing on specific changes in the oil chemistry to verify the degradation rate increase provided by the added nutrient. Such a sophisticated approach was required because of the problems inherent with measurement of total petroleum hydrocarbon in the sediment to define the degradation rate. Results show that the rate of oil biodegradation on fertilized beaches was from three to more than five times faster than on unfertilized beaches.
This paper summarizes the bioremediation research conducted, and the extensive information obtained. The experience gained by Exxon, including pioneering work on internal markers, applies directly to bioremediation studies in other environments. Some of this experience is being extended to the remediation of inland contaminated sites and there is a major effort now underway to identify low-cost bioremediation techniques for in-situ restoration of such sites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.