This Natural Coral Reef Thermostat Is Being Broken By Climate Change

Source: Hakai Magazine/Richard Kemeny 

Photo: Alexander Vasenin/Wikimedia Commons

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The 2,300-kilometer Great Barrier Reef fringing Australia’s northeast coast might function like a giant thermostat, regulating the temperature of its environment. Yet as scientists work to uncover more about this built-in mechanism, climate change might be breaking it.

In the late 1980s, a group of scientists hypothesized that some phytoplankton and algae, including the zooxanthellae that live in corals, employ a biological feedback loop that might control the water temperature around them. When stressed by heat, zooxanthellae produce compounds that make a gas called dimethyl sulfide (DMS), which creates an aerosol layer just above the water. The fine particles in this aerosol layer scatter sunlight. They also act as the nuclei for the formation of tiny water droplets that tend to make low, bright clouds that shade and cool the water’s surface.

While all the steps in the feedback loop are known, it isn’t clear whether coral algae can actually regulate the temperature of their environment in this way. For instance, they may not trigger the production of enough DMS to make a difference, or perhaps something more complex is going on and temperature dampening doesn’t happen at all.

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Photo: Alexander Vasenin/Wikimedia Commons

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