Coral reef survival under accelerating ocean deoxygenation

Abstract

Global warming and local eutrophication simultaneously lower oxygen (O2) saturation and increase biological O2 demands to cause deoxygenation. Tropical shallow waters, and their coral reefs, are particularly vulnerable to extreme low O2 (hypoxia) events. These events can drive mass mortality of reef biota; however, they currently remain unaccounted for when considering coral reef persistence under local environmental alterations and global climatic change. In this Perspective, we integrate existing biological, ecological and geochemical evidence to consider how O2 availability and hypoxia affect reef biota, with particular focus on the ecosystem architects, reef-building corals, that operate as both O2 consumers and producers. We pinpoint fundamental knowledge gaps and highlight the need to understand sub-lethal hypoxia effects that are likely already in play.