Description: The central and western part of the Sea of Marmara consists of two deep pull-apart-basins and an intermediate push-up structure. The bathymétric high between the Tekirdag and the Central Marmara Basin is cut by a deep E-W-trending furrow which is the eastern branch of the Ganos Fault which in turn is part of the active North Anatolian Fracture Zone. This area was mapped during the Meteor cruise M 44/1 in February 1999. During the cruise seafloor observations and sediment coring within this prominent furrow structure have shown that methane is emanating at several sites into the water column and that the sediments are also methane-enriched in their deeper parts. Within the porewater regime of hemipelagic clay sediments the typical process of bacterially mediated anoxic methane oxidation is taking place. The resulting geochemical profiles indicate a reaction-zone in a depth of several meters where methane is oxidized to H2 and CO2; the H2 reduces the sulfate that finally is converted to H2S. This H2S forms iron-sulfide precipitates in the presence of reduced iron. However, our geochemical concentration profiles are not typical for steady-state conditions, but are rather characterized by a very steep drop in sulfate-concentrations just above the reaction zone. We suggest that this specific gradient is caused by a situation that is superimposed by an advective upward-migration of a methane-enriched fluid. This advective fluid flow is controlled by the tectonic strain of the Ganos Fault system.

Description: There is a strong economic interest in commercial deep‐sea mining of polymetallic nodules and therefore a need to define suitable preservation zones in the abyssal plain of the Clarion Clipperton Fracture Zone (CCZ). However, besides ship‐based multibeam data, only sparse continuous environmental information is available over large geographic scales. We test the potential of modelling meiofauna abundance and diversity on high taxonomic level on large geographic scale using a random forest approach. Ship‐based multibeam bathymetry and backscatter signal are the only sources for 11 predictor variables, as well as the modelled abundance of polymetallic nodules on the seafloor. Continuous meiofauna predictions have been combined with all available environmental variables and classified into classes representing abyssal habitats using k‐means clustering. Results show that ship‐based, multibeam‐derived predictors can be used to calculate predictive models for meiofauna distribution on a large geographic scale. Predicted distribution varies between the different meiofauna response variables. To evaluate predictions, random forest regressions were additionally computed with 1,000 replicates, integrating varying numbers of sampling positions and parallel samples per site. Higher numbers of parallel samples are especially useful to smoothen the influence of the remarkable variability of meiofauna distribution on a small scale. However, a high number of sampling positions is even more important, integrating a greater amount of natural variability of environmental conditions into the model. Synthesis and applications. Polymetallic nodule exploration contractors are required to define potential mining and preservation zones within their licence area. The biodiversity and the environment of preservation zones should be representative of the sites that will be impacted by mining. Our predicted distributions of meiofauna and the derived habitat maps are an essential first step to enable the identification of areas with similar ecological conditions. In this way, it is possible to define preservation zones not only based on expert opinion and environmental proxies but also integrating evidence from the distribution of benthic communities.