Coral reefs, the most diverse and productive ecosystems on the planet, are facing a global tragedy as unprecedented heat stress causes bleaching and death across the Americas. Scientists warn that this could become a worldwide event if greenhouse gas emissions are not reduced.
Coral bleaching occurs when corals expel the symbiotic algae that live in their tissues and provide them with nutrients and oxygen. This makes the corals lose their color and become more vulnerable to diseases and death. Bleaching is triggered by environmental stress, such as high water temperatures, pollution, or overfishing.
According to Coral Reef Watch, a program of the US National Oceanic and Atmospheric Administration (NOAA), coral reefs in several countries in North and Central America, including Mexico, Belize, Honduras, Panama, Colombia, and Costa Rica, are experiencing severe bleaching and dying due to heat stress. The program uses satellite data and models to monitor and predict coral bleaching events.
“I don’t think any of these places have seen heat stress like this before,” said Dr Derek Manzello, coordinator of Coral Reef Watch at the US National Oceanic and Atmospheric Administration.
Coral reefs are home to more than 25% of marine life and provide essential services to humans, such as food, tourism, coastal protection, and medicine. They are estimated to be worth $375 billion per year globally. However, they are also among the most threatened ecosystems by climate change, as they are sensitive to changes in temperature, acidity, and oxygen levels.
Scientists are working on finding ways to protect corals from heat stress and coral bleaching. Some of the promising approaches involve using probiotics or training corals to tolerate higher temperatures.
Probiotics are beneficial microorganisms that can enhance the health and resilience of corals by improving their nutrition, immunity, or symbiosis with algae. Probiotics can be introduced to the corals or modified in their existing microbiome. “Probiotics are not a silver bullet for saving coral reefs from climate change, but they could be a valuable tool to increase coral health and resilience,” said Dr. Claudia Pogoreutz, researcher at GEOMAR Helmholtz Centre for Ocean Research Kiel.
Training corals involves exposing them to gradually increasing temperatures over several weeks. This induces a process called acclimatization, which allows the corals to adjust their physiology and gene expression to cope with the heat. “Our study shows that corals can adjust to higher temperatures in a matter of weeks, not years or decades as previously thought. This gives us hope that some corals may survive the climate crisis if we manage to reduce greenhouse gas emissions,” said Prof. Oren Levy, director of the Mina and Everard Goodman Faculty of Life Sciences at Bar-Ilan University.
Another approach is to consider the biological interactions and feedbacks among different reef organisms, such as algae, fish, worms, and bacteria. These interactions can influence the response of corals to environmental stress and affect their recovery after bleaching. “Protecting coral reefs more effectively from climate change requires a holistic approach that considers not only the physical environment but also the biological environment,” said Dr. Christian Voolstra, professor of biology at the University of Konstanz.
Scientists hope that these innovative methods can help save coral reefs from extinction. However, they also emphasize that reducing greenhouse gas emissions is the most urgent and effective way to prevent further coral bleaching and death. They hope that this tragedy will motivate and unite people to take action on climate change.
– ‘Huge’ coral bleaching unfolding across the Americas prompts fears of global tragedy, The Guardian, 11 August 2023
– Protecting coral from heat stress and coral bleaching: Probiotic approaches could protect corals against heat stress, ScienceDaily, 7 May 2021
– Protecting coral reefs more effectively from climate change, ScienceDaily, 11 August 2021
– Corals can be ‘trained’ to tolerate heat stress, ScienceDaily, 2 March 2022.