HYPOX- Cruise No. MSM 15/1 - April 12 - May 08, 2010 - Istanbul (Turkey) - Istanbul (Turkey) (English)

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Hypoxic conditions in aquatic ecosystems will increase in dimension and frequency as a consequence of global change. Ocean warming decreases oxygen concentrations, increases the stratification of water bodies and decreases the deep-water circulation. In combination with eutrophication, strong feed-back mechanisms are observed, leading to a further decrease in oxygen availability, to a decline of the water quality and the health of aquatic ecosystems, and to an increased production of greenhouse gases. The research cruise MSM 15/1 was a major activity of the Project HYPOX In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and land-locked water bodies of the EU 7th framework program ENV.2008. Monitoring and observing oxygen depletion throughout the different Earth system components. HYPOX investigates the effect of oxygen depletion on biogeochemical processes in aquatic ecosystems. Hence, the research cruise HYPOX (MSM 15/1) aimed to quantify the concentration and uptake of oxygen at the anoxic boundaries in the water column and at the sediment water interface of the Black Sea, in parallel with the measurement of nitrogen, carbon, sulfur and iron fluxes. The Black Sea is an ideal study system for this purpose: The high productivity and export of organic matter has lead to the formation of the largest anoxic basin on earth. The limited exchange of water between the Black Sea and the Mediterranean through the Istanbul Strait and the strong freshwater input by the rivers of the Black Sea catchment area cause a strong pycnocline and chemocline in 50-100 m water depth. Climate change in combination with increasing nutrient input causes strong regional effects. The warm, saline and oxygen-rich Mediterranean water flows from Istanbul Strait below the less dense water masses in the Black Sea. Oxygen-rich filaments reach beneath the pycnocline and strongly influence biogeochemistry. Climate change is expected to affect the transport of Mediterranean water into the Black Sea with important consequences for the ecosystems and their functioning. Off the Crimean peninsula, strong variations in oxygen and sulphide concentrations were observed in 130-165 m depth, caused by regional circulation patterns. Internal waves cause the temporary aeration of anoxic areas of the shelf or transport poisonous sulfide into suboxic and hypoxic depths, thus affecting the benthic community. In addition to the aims of the HYPOX project, the expedition contributed to the Global Earth Observation System of Systems (GEOSS) and to the network programs ESONET and EMSO, by using newly developed underwater technology for long-term measurements of oxygen and other elements. During the research cruise MSM 15/1 we successfully used new in situ observatories and new research methods to investigate the temporal and spatial dynamics of transport and turnover rates of oxygen and sulphide, and their effects on the biogeochemistry and the diversity of the pelagic and benthic communities.