Gulf of Corinth IODP Expedition 381 Inorganic Geochemistry

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The Gulf of Corinth has experienced repeated changes from a lake to a marine embayment in response to sea level fluctuations during the last ice ages. Such dramatic environmental changes will have strongly affected the ecosystem in the Gulf of Corinth, and with it the cycling of bioessential elements like carbon and phosphorus. In similar situations where a lake was flooded and gradually salinified by the incursion of seawater, like in the Black Sea or Baltic Sea at the end of the last ice age, very distinct geochemical regimes developed in the water column that had strong impacts on the chemistry of the water column: A stable stratification developed between fresh lake waters on top and saline seawater below, and this restricted mixing of the water column. As a result, the deep waters became completely free of oxygen, and thus inhospitable to multi-cellular life - even poisonous due to the production of hydrogen sulphide. It is currently unknown if the Gulf of Corinth experienced similarly dramatic environmental changes and the development of an oxygen-free deep water mass. If so, this would have had important implications for the preservation of organic carbon in the sediments - the raw material for our modern oil and gas resources - as organic matter is much less degraded under oxygen-depriven conditions. Our geochemical methods will allow usfor the first time, to track changes in water column and sediment chemistry across a couple of representative lake-to-ocean and ocean-to-lake transitions in the Gulf of Corinth.