Microbes have a surprising influence on coral bleaching

Coral reefs are vibrant underwater ecosystems teeming with life. But they’re facing a major threat: coral bleaching, triggered by rising water temperatures. This phenomenon causes corals to expel the algae living within their tissues, leaving them vulnerable to death.

New research from Guangxi University reveals that microbes living within corals might hold the key to their survival.

Microbes and coral bleaching

Reefs are ecosystems built by tiny animals called corals. Microscopic organisms, including bacteria, fungi, and algae, live inside coral tissues in a mutually beneficial relationship. 

These tiny microbes help the corals obtain nutrients, produce food using sunlight, and resist environmental damage. However, if the water temperature rises excessively, the corals expel the algae, causing them to lose their color and essential nutrients, known as coral bleaching.

Focus of the study

The researchers studied the microscopic organisms residing within corals found in the South China Sea. The goal of the investigation was to determine how microbes may influence a reef’s resistance to coral bleaching.

The team examined 18 different coral species and discovered patterns within the communities of microscopic organisms living inside them. These patterns were linked to the coral’s susceptibility to bleaching. 

The dual role of microbes

The study revealed that corals which are resistant to bleaching often have many heat-resistant Symbiodiniaceae in their tissues. This algae is essential for the coral’s survival, as it helps them tolerate warmer water.

On the other hand, corals that are more prone to bleaching were found to have a wider variety of fungi, including some that might be harmful. 

This finding indicates that the health of corals is strongly linked to the makeup of their microscopic companions. Corals with a diverse community of heat-resistant algae are better equipped to handle the challenges of climate change. 

“Our study highlights the ecological effects of microbiome dynamics and interactions between Symbiodiniaceae and fungi on coral thermal bleaching susceptibility, providing insights into the role of microorganisms and their interaction as drivers of interspecific differences in coral thermal bleaching,” explained study lead author Biao Chen, an assistant professor at Guangxi University.

Far-reaching impacts of coral bleaching

If coral bleaching becomes more frequent, it could have significant consequences for both the environment and human societies. Coral bleaching poses a threat to marine life, jobs, and even the safety of coastal communities.

Bleaching causes coral reefs to lose their richness and variety. This translates to fewer fish and other sea creatures, impacting the livelihoods of fishers and people who depend on the ocean for food. 

Tourism, which thrives on the beauty and exploration of these vibrant underwater worlds, would also decline with increased bleaching events. 

Furthermore, coral reefs act as natural barriers, protecting coastlines from powerful waves and storms. Without this protection, beaches could erode, and coastal areas would be more vulnerable to storm damage. 

Learning how microbes help corals

The study emphasizes the importance of coral microbiome – the collective of microorganisms living with corals. 

The scientists propose creating a global database of coral reef microbial communities and conducting further research across various disciplines, including ecology, marine chemistry, and oceanography. This can provide deeper insights into how microbes can help coral reefs adapt and survive in a warming world.

The research provides a roadmap for developing new ways to save coral reefs, which could involve changing the makeup of the tiny organisms living inside them. 

The study is published in the journal Applied and Environmental Microbiology.

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