Hydrothermalism and Deep-Water Ecosystems in the Atlantic Ocean (MSM 6 - Koordinatorantrag)

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RV MARIA S. MERIAN cruise MSM 06 comprises three legs that cover a large part of the Atlantic Ocean (Fig. 1). Starting at the Faroer Islands the first leg concentrates on cold-water coral ecosystems in the Gulf of Cadiz where these ecosystems seem to be related to mud volcanoes. The major aim of this leg is to detect the main forcing factors driving the distribution of the corals and to investigate how these ecosystems developed under changing environmental conditions in the past. The second and the third leg both will concentrate on the investigation of hydrothermal systems. Leg 2 will bring the RV MARIA S. MERIAN to the Logatchev hydrothermal field at the Mid-Atlantic Ridge in the western North Atlantic, where a locally focused study is planned to explore the causes for temporal and spatial compositional differences of hydrothermal fluids and their effect on the vent communities in this vent field. Leg 3 will focus on another section of the Mid-Atlantic Ridge further to the east and just south of the equator. There several topics related to the influences of large-scale magmatic and tectonic processes on hydrothermal systems will be investigated in four distinct vent fields. To achieve the ambiguous set-out goals, especially the very detailed investigation of sea floor settings inevitable to reach these goals, all three legs will employ a remotely operated vehicle (ROV) as the main scientific instrument underlining how new technologies enable scientific work on a hitherto impossible level of detail.MSM 06/1: The focus of the first leg is on the investigation of cold-water coral ecosystems in the Gulf of Cadiz. Random findings of cold-water corals on mud volcanoes have shown that these topographic structures in the Gulf of Cadiz can serve as habitats for cold-water corals. From these findings it seems that their regional distribution is limited to a depth interval of 600 to 1350 m. By employing the Bremen ROV CHEROKEE, the camera sledge OFOS (Ocean Floor Observation System) and a video-guided grab sampler, the main aim of this leg is to identify and to evaluate those factors that control the distribution of cold-water corals in this region. Detailed video observations on individual structures will provide clues about the small scale distribution (and in their sum on the large scale distribution) of the corals in relation to the topographic and oceanographic settings and on the faunal communities the corals are associated with. The video observations and related bathymetric and oceanographic investigations will be complemented by targeted fauna and sediment sampling by the ROV, video-directed grab sampling as well as by standard sampling methods. In addition, sediment cores will be retrieved to study the development of these cold-water coral ecosystems under changing environmental conditions, e.g. over glacial/interglacial changes. This expedition contributes to the HERMES project, an integrated project funded within the 6th FRP of the European Union.MSM 06/2: The overall goal of the second leg - to be conducted under the auspices of the DFG SPP 1144 - is the investigation of causes for temporal and spatial compositional differences of hydrothermal fluids and their effect on the vent communities in the Logatchev