Abstract
Global warming and local eutrophication simultaneously lower oxygen (O-2) saturation and increase biological O-2 demands to cause deoxygenation. Tropical shallow waters, and their coral reefs, are particularly vulnerable to extreme low O-2 (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 O-2 availability and hypoxia affect reef biota, with particular focus on the ecosystem architects, reef-building corals, that operate as both O-2 consumers and producers. We pinpoint fundamental knowledge gaps and highlight the need to understand sub-lethal hypoxia effects that are likely already in play.
Climate change and other human activities are decreasing ocean oxygen content. This Perspective considers the limited data on effects to coral reefs, including oxygen thresholds for lethal and sub-lethal effects in coral reef taxa, and proposes key research questions to address this critical issue.