Some corals survive warming waters by 'remembering' heat waves

A recent study conducted by scientists at Oregon State University sheds light on the ability of certain coral species to withstand marine heat waves by “remembering” previous events. This phenomenon, known as ecological memory, appears to be intricately linked to the microbial communities living within the corals.

Importance of coral resilience

Alex Vompe, the study’s lead author and a doctoral student under microbiology professor Rebecca Vega Thurber, emphasized the importance of this finding.

“Coral reefs are vital to our planet’s ecosystem, but they face significant threats from various human-induced pressures, including climate change,” Vompe stated. He highlighted the urgent need to understand how reefs adapt to increasing and repeated disturbances like marine heat waves, pointing out the potential role of coral microbiomes in this rapid adaptation process.

The study arrives at a critical time as marine heat waves are expected to become more frequent and severe due to climate change. Understanding and enhancing coral resilience is a key conservation goal.

Vompe notes that recognizing the role microbes play in coral adaptation can significantly impact coral gardening and planting efforts. He also suggests that a deeper grasp of microbial processes and the organisms responsible for ecological memory could aid in developing probiotics or monitoring protocols to enhance coral health.

Understanding the coral microbiome

Corals, though occupying less than 1% of the ocean, are home to nearly a quarter of all marine species. They play a crucial role in regulating the sea’s carbon dioxide levels and are invaluable for scientific research, particularly in medicine.

These fascinating organisms, consisting of interconnected polyps, house not only microscopic algae but also a diverse array of bacteria, viruses, archaea, and microeukaryotes, collectively known as the coral microbiome.

The symbiotic relationships within the coral reef ecosystem are foundational. Microbes assist coral hosts in various vital functions, including cycling of essential elements and protection against pathogens. In return, the coral polyps provide nutrients and shelter to these microbes.

Coral reefs and climate change

However, climate change poses a significant threat to these delicate relationships, with warming oceans potentially leading to the collapse of these symbiotic partnerships, a phenomenon known as coral bleaching. But, as Vompe points out, there is a glimmer of hope.

“Acropora retusa, a prevalent coral species in the Mo’orean coral reef, displays a powerful ecological memory response to heat waves, hinting at a greater resilience to climate change than previously thought,” he explains.

This conclusion was drawn from a five-year study conducted by Vompe, Vega Thurber, and their colleagues from various universities. They examined 200 coral colonies in a reef on the north shore of Mo’orea, French Polynesia, which had undergone a drastic ecological reset in 2010 due to natural disasters.

This unique setting allowed the researchers to closely observe the coral’s response to consecutive heat waves in 2016, 2017, 2018-2019, and 2020.

Some corals survive bleaching by “remembering”

Vega Thurber noted that some coral species seemed to maintain better health during subsequent heat waves, likely due to their exposure to past events. “The memory response of Acropora retusa was strongly linked to changes in its microbiome, supporting the idea that the microbial community plays a part in this process,” she said.

Cauliflower corals in the genus Pocillopora also demonstrated resilience. Despite the initial disturbance caused by the 2019 heat wave, they recovered to their pre-disturbance state, even amidst the subsequent 2020 heat wave. The corals seemed to “remember” how to survive.

Vega Thurber attributes this resilience to the unique biological features of coral microbial communities. These include short generation cycles and large population sizes, which enhance adaptability and responsiveness to environmental change.

“In two of the three coral species we focused on, we observed initial microbiome resilience, host and microbiome acclimatization, or developed microbiome resistance to repeated heat stress,” Vega Thurber concluded. “These patterns are consistent with the concept of ecological memory, highlighting the critical role of the microbiome in coral resilience.”

In summary, this research not only sheds light on the complex interactions within coral ecosystems but also opens new avenues for conservation efforts and strategies to combat the effects of climate change on these vital organisms.

The full study, funded by the National Science Foundation, was published in Global Change Biology,

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