METROL

project

goals

The deposition of organic material on the sea floor and its burial below the sulfate zone is the basis for a microbiological production of vast amounts of methane. Methane is an aggressive greenhouse gas when emitted into the atmosphere. The continuous methane formation in European margin sediments may lead to accumulations of free gas, to enhanced methane emission, and to complex carbonate structures. These consequences of marine methane cycling are important for environmental quality, for climate development, and for off-shore operations of the hydrocarbon industry.

The goal of the

project is to understand the controls and mechanisms of methane production and breakdown in ocean margin sediments. The microbiological key process of sub-surface methane oxidation accounts for perhaps 90% of the entire methane flux in the sea floor and, therefore, plays a critical role as a barrier against methane emission. The efficiency of this methane oxidation and its environmental regulation are, however, still poorly constrained due to lack of relevant data and of understanding of the controlling factors. Even at methane seeps and surficial gas hydrates an unknown -- but probably major -- part of the methane is biologically oxidized before it can escape into the water column. The efficiency of this process must be understood if we are to quantify current methane fluxes in marine sediments and predict the effect of environmental change on sea floor methane release.

aims at

understanding the processes and the controls on the process involved in the microbial oxidation of methane,

carefully and thoroughly quantifying the rates of turnover and fluxes of methane, sulfate and other intermediates at the methane sulfate transition,

exploring these relationships through the use of a reaction-transport diagenetic model, and

The main objectives of METROL are:

To establish high-quality data on the processes responsible for the formation, accumulation, transport and oxidation of methane in selected European margin sediments.

To determine the position and efficiency of the sub-surface methane barrier relative to the total carbon flux.

To identify, through 16S rDNA-based techniques and isotopic biomarker analyses, the microbial populations responsible for methane oxidation.

To develop analytical and predictive models on the complex processes determining methane fluxes in the sea floor and their regulation by environmental change

To acoustically map the accumulation of methane gas in selected ocean margin sediments and to explore the applicability of such data for environmental survey and monitoring of long-term organic loading.

To establish a data base on biogeochemical key parameters determining the methane flux and retention in marine sediments based on the new data and on existing data and literature.

To establish a web site which includes an interactive access to the data base, to informative GIS-based maps and graphs of the data, and to a practical modeling tool for calculating the controls on methane fluxes in ocean margin sediments. The model will be validated on the basis of existing data and new detailed data on the critical processes and parameters.

To provide a public knowledge base on the above aspects of the marine methane cycle and to transfer this knowledge to users by cooperation with an oil company and an environmental agency as partners in METROL.

To provide new data and improved process understanding for the marine methane and carbon budget in global climate models.