Low oxygen conditions (hypoxia) are becoming increasingly common in aquatic systems worldwide. While hypoxia can occur naturally due to stratification, eutrophication and limited bottom water renewal, there is strong evidence for a world-wide increase in hypoxia linked to human-activities and climate-change. This is a major issue because oxygen depletion leads to mortality of benthic fauna and major changes in ecosystem functioning. Key examples of modern oxygen-deficient “dead zones” in coastal areas are the Gulf of Mexico, the East China Sea, the Black Sea and the Baltic Sea as well as numerous fjords, lagoons and lakes. Oxygen Minimum Zones (OMZ) in the open ocean are developed along the eastern edges of the Worlds' oceans, and thus occur on the continental margins of countries such as Peru, Chile, Namibia, Pakistan and India. Areas where there is evidence that OMZs are currently expanding include the eastern Atlantic and equatorial Pacific. While true anoxia in the modern ocean is rare, wide-spread anoxia occurred episodically in the oceans during so-called oceanic anoxic events (OAEs) in Earth’s past.

Numerous questions remain regarding the mechanisms driving hypoxia and anoxia in coastal and open ocean systems in the present and past, the role of natural processes versus human activities and the potential and timeline for (eco-) system recovery. This session aims to bring together researchers studying a broad range of aspects linked to oxygen depletion in modern and ancient settings. We encourage contributions from both experimentalists and modelers from a wide range of fields, including biogeochemistry, paleo-oceanography, biology, sedimentology and paleontology.