Coral reef research has focused on the twin evils birthed by record-high greenhouse gas emissions: warming oceans and increasingly acidic seawater. These global threats are caused by seawater absorbing the excess heat and carbon dioxide that fossil fuel burning has added to the atmosphere. But there is another consequence that is seldom discussed.
Globally, oceanic oxygen is being depleted because seawater holds less oxygen as it heats up. In the warm coastal waters where tropical coral reefs grow, the immediate effects of low oxygen concentrations can be catastrophic. Short-term hypoxia events are increasingly reported in which dissolved oxygen levels suddenly plummet – often triggered or exacerbated by chemical pollution running off the land, like nutrient-rich fertilisers – which can kill entire coral communities and decimate reefs within days.
