RAPID:Rates and mechanisms controlling the microbial degradation of crude oil from the MC252 spill in Gulf of Mexico beach sands

Florida State University, Tallahassee FL

Investigators

Abstract

With funding through this Grant for Rapid Response Research (RAPID), scientists at the Florida State University will study the transport and biodegradation of Deepwater Horizon crude oil in Gulf beach sands. The study will place emphasis on the sediment clogging caused by oil filtration and ensuing changes to the structure and function of indigenous microbial communities. Although the process of oil contamination of beaches has been investigated in great detail, little is known about the effect of crude oil on beach filtration and the effect of oil-related reduction of beach pore water flows on oil transport and microbial degradation within the sandy sediment. This filtration process, caused by wave set up and tidal water level changes, constitutes an effective pumping mechanism that can drive low-viscosity crude oil and detergent-oil mixtures deep into beach sediments. Oil transport into deeper, anoxic layers may decrease oil degradation rates, thereby extending the period of toxin release to nearshore waters. Goals of the project are to assess 1) how much and how deep oil is filtered into the beach, 2) how oil alters the beach filtration rate and thereby sediment oxygenation, 4) how oil contamination changes structure and function of the sand microbial community and 5) which factors regulate oil degradation by microbial communities in marine sands. To quantify these processes, sets of sediment cores will be taken at time intervals along a short transect from the supralittoral to the sublittoral zone at a sandy beach in the Northeastern Gulf of Mexico. The sediment will be analyzed for oil content (amount, composition and distribution), sediment characteristics (permeability, porosity, grain size spectrum, oxygen penetration), and the microbial community (composition and activity). Oil will be characterized using a GC-MS. Changes in microbial community composition and activity will be assessed using a combination of culture-based and cultivation-independent molecular techniques. The results will quantify the uptake of oil and detergent-oil mixtures into Gulf sand beaches, the effect of these substances on sediment physical and biogeochemical properties, the response of the sedimentary microbial community, and oil degradation rates. Broader Impacts: The sandy beaches of the Northeastern Gulf of Mexico are of high ecological and economical value as they are biotope, foraging and breeding area of a large number species, and present a main tourist attraction. Tourism is Florida?s largest sector of the state economy with about 60 million visitors every year and a $57 billion impact. The pollution of the beaches by crude oil thus presents a major threat to Florida?s economy. Previous research indicates that oil can penetrate deep into sandy beaches, which may change microbial community activities and decrease the oil degradation rates. Consequences include toxin release from such beaches extending over many years. Understanding the uptake, transport and degradation of oil in sandy Gulf beaches is prerequisite for designing clean up and remediation procedures. Research of this project focuses on pristine Gulf beaches for which no data on oil penetration and degradation exist and that now are threatened by the Deepwater Horizon disaster. The project combines research with education and training of two graduate students. Project results will be published in scientific journals, local outlets and the internet. The data collected in this rapid response project will provide data for a proposal of a three year project focusing on transport and degradation of crude oil components in permeable shore sediments. The project goal is to generate quantitative data that permit forecasting of the oil degradation process and optimization of bioremediation procedures.