Biology and biogeochemistry of the Eastern Mediterranean Sea - Cruise No. M71 - December 11, 2006 - February 4, 2007 - Heraklion (Greece) - Istanbul (Turkey) (English)

R/V METEOR cruise 71 had a total of 50 ship days on 3 individual legs in the Eastern Mediterranean Sea. Research was directed towards investigations into deep-sea biology and biogeochemistry of this oligotrophic ocean basin. The first leg (M71-1) studied the oceanographic setting, sphere of influence, and biological habitat characteristics of a chain of seamounts in the northern Levantine Basin (Anaximander Mountains) with a combination of hydrographical investigations by CTD casts, benthic observations, and benthic sampling methods. The primary goal was to assess if a seamount ecosystem in an oligotrophic region with a warm deep-water layer is comparable with similar topographic features in the NE-Atlantic, which were investigated within the EU funded project OASIS. In particular, the study aimed at possible differences or similarities between these systems in different oceanographic regimes with respect to their impacts on the current field and on the particle flux, to their productivity, the distribution of their food webs and their sphere of interference. A further goal of the cruise was to extend a time series of zooplankton distribution and composition in eastern Mediterranean basins, which in particular monitors the effect of the EMT (Eastern Mediterranean Transient) on the plankton communities. The second leg (M71-2) examined deep-sea biological diversity in two seafloor areas south of the island of Crete that differed in proximity to land, and aimed to distinguish controls on deepsea benthic communities by a combined biological, genetic and oceanographic research programme. The main goal was to establish species composition, diversity and dominance patterns of benthic deep sea communities of the Levantine Basin. In every one of the two working areas of different depth and distance to the Cretan coast (area 1 very deep and adjacent to the coast, area 2 less deep and farther away), 3 stations were sampled for organisms of all size classes (microbes and nanofauna to megafauna). Measurements of abiotic and biochemical parameters in the deep sea sediments allowed to correlate these data with biological factors using community-based multivariate statistics. The collected organisms will be identified to species level in order to be able to compare the stations. These investigations aimed to assess if individual samples are representative for the entire community in order to perform sound comparisons on this basis. Especially the hypothesis that benthic deep sea diversity and productivity depend on the distance from the coast rather than on water depth was to be tested. The final leg (M71-3) occupied a series of 17 stations across all basins of the Eastern Mediterranean Sea in order to perform in-situ experiments and to obtain water, biological materials, suspended matter, and surface sediment samples. The scientific goals were to explore the effects and temporal evolution of deep water masses in the Ionian Basin, to search for reasons for unusual nutrient element ratios in the Eastern Mediterranean Sea, to analyse the stable isotope composition of different (dissolved and particulate) N-bearing compounds, and to perform experiments to elucidated nutrient limitations for growth of phytoplankton and heterotrophic bacteria. Subsequent onshore investigations will clarify the reasons for unusual nutrient ratios and stable isotope ratios in the oligotrophic Eastern Mediterranean Sea. The cruise was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF).