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Marine deoxygenation is increasingly recognized as a major environmental threat. Global warming leads a substantial part of this deoxygenation trend and, it is foreseen to exacerbate during the next decades both in the open ocean and in the coastal waters, which are additionally exposed to increasing anthropogenic pressure. The number of affected coastal systems is already growing exponentially and the most recent assessments of oceanic deoxygenation show the highest rates. Two main challenges are thus addressed to the scientific community: 1) To understand and predict the response of global biogeochemical cycles to deoxygenation. In particular, to clarify how the disturbance induced by lower oxygen conditions on nitrogen and phosphorus cycles across the estuarine-shelves-ocean continuum may feedback on climate systems and on oxygen balance. 2) To evaluate and mitigate the threat posed by deoxygenation on essential and valuable marine goods and services and on marine biodiversity. Open ocean and coastal deoxygenation differ in terms of temporal scale, morphology, driving processes and implications. However, we consider it opportune to gather contributions related to both typologies in order to highlight interactions and common processes, and to promote the synoptic perception of marine deoxygenation required for public awareness and preluding the development of specific mitigation strategies.

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English