Experimental coral reef communities transform yet persist under mitigated future ocean warming and acidification

Area of Science:

• Marine Biology
• Climate Change Ecology
• Oceanography

Background:

• Coral reefs are highly sensitive to ocean warming and acidification, facing predicted collapse.
• Current models project a shift from biodiverse calcifier-dominated systems to low-biodiversity algal systems.
• These changes threaten the persistence of coral reef ecosystems globally.

Purpose of the Study:

• To experimentally assess the response of coral reef mesocosm communities to projected future ocean conditions.
• To investigate the impacts of warming (+2 °C), acidification (-0.2 pH), and combined stressors.
• To evaluate the potential for coral reef persistence under climate change scenarios.

Main Methods:

• A two-year experimental study using entire mesocosm coral reef communities.
• Application of controlled warming (+2 °C) and acidification (-0.2 pH) treatments.
• Analysis of community structure and composition shifts under future ocean conditions.

Main Results:

• Contrary to model projections, coral reef communities persisted under combined warming and acidification.
• Communities shifted in structure and composition, forming novel calcifying ecosystems.
• High biodiversity was maintained in these altered, yet persistent, ecosystems.

Conclusions:

• Coral reef ecosystems can persist as altered calcifying systems, rather than collapse, under future ocean conditions.
• Limiting global warming to Paris Climate Agreement targets is crucial for coral reef survival.
• These findings challenge previous predictions and offer a more optimistic outlook for reef persistence.