Another important issue in the framework of the project was the investigation of the microbially mediated methane turnover in the zones of methane accumulation within the sediment.
Main cruise objectives:
(Click here for more information on research goals)
Three working areas were chosen according to existing information on gas seeps distribution, accumulations of free gas in the sediment, and sediment geochemistry:
1 - Danube Canyon
2 - North-western shelf
3 - Paleo-Dniepr area
The Danube Canyon (also known as Viteaz Canyon) has developed seaward of the late Pleistocene paleo–Danube Valley and stretches on the outer north western Black Sea shelf to the shelf break. Aggregations of methane seeps have been mapped along the canyon slope and adjacent areas; Subsurface gas plumes have been mapped in sediments in the canyon and along its prolongation (Popescu et al. 2004); further information on subsurface gas distribution is available by sub-bottom profiles from project partner GeoEcoMar.
A number of gas seeps have been mapped in water depths between 100 and 300 m along the entire north western shelf break between the Danube Canyon and the paleo-Dniepr delta area (Egorov et al. 1998). Dense accumulations of seep positions are known from the area around 44°35’N 31°10’E. This area mainly served for the search for gas seeps and associated carbonate precipitating microbial mats.
The paleo-Dniepr area has been intensively mapped for gas seep positions (e.g. Egorov et al. 1998) and has already been visited by other research cruises in the recent past (e.g. with RV Logatchev in 2001, RV Vodyianitskiy in 2003, 2004). On the basis of existing information on subsurface gas distribution, further high resolution chirp echo-sounding and analyses of sediment geochemistry and microbial processes was planned in order to study the relationships between the presence and distribution of free gas and the microbially mediated gas turnover in the pore water. Another important task was the further exploration for microbial mat communities comparable to those of the spectacular chimney forest discovered by the submersible JAGO in 2001 with RV Logatchev (Michaelis et al. 2002).
Working areas 1 and 2 have not been subjected to submersible dive operations before.
Click on thumbnail to enlarge cruise track of P317/3
Egorov, V., Luth, U., Luth C., Gulin, M.B. (1998): Gas seeps in the submarine Dnieper Canyon, Black Sea: acoustic, video and trawl data. In Luth, U., Luth, C., Thiel, H., (Eds.), MEGASEEPS Gas Explorations in the Black Sea, Project Report. Zentrum für Meres- und Klimaforschung der Univ. Hamburg. Hamburg. 11-21.
Michaelis, W., Seifert, R., Nauhaus, K., Treude, T., Thiel, V., Blumenberg, M., Knittel, K., Gieseke, A., Peterknecht, K., Pape, T., Boetius, A., Amann, R., Jørgensen, B.B., Widdel, F., Peckmann, J., Pimenov, N.V., Gulin, M.B. (2002): Microbial reefs in the Black Sea fueled by anaerobic oxidation of methane. Science 297, 1013-1015.
Popescu, I., Lericolais, G., Panin, C., Normand, A., Dinud, C., Le Drezen, E. (2003): The Danube submarine canyon (Black Sea): morphology and sedimentary processes. Marine Geology 206, 249–265.