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Cold-water corals build mountains to battle climate change 

Cold-water corals are found in the depths of the world’s oceans, hundreds of meters below the surface. These corals are far removed from the sunlit environments that nurture vibrant tropical reefs.

A new study from the University of Groningen reveals the extraordinary lengths to which cold-water corals go to survive and flourish, even as they face the looming threat of climate change.

Shadowy realms 

Unlike their tropical counterparts, cold-water corals do not bask in sunlight nor engage in a symbiotic relationship with algae for their brilliant hues. Instead, they reside in the shadowy realms off coasts like Ireland’s, creating their own spectacular ecosystems vital to the ocean’s health. 

Underwater mountains 

The new study, led by theoretical ecologist Anna van der Kaaden, highlights a peculiar behavior of these corals. In their quest for sustenance, they build vast underwater mountains, elevating themselves to capture more food carried by ocean currents. 

These structures, formed over millennia, can surpass the height of the Eiffel Tower, showcasing the corals as “ecosystem engineers” who modify their environment to their advantage.

A potential trap

The irony of these monumental efforts is the potential trap they create for themselves. As Van der Kaaden points out, the very mountains that offer them abundant food and life might become their prisons. With the onset of climate change, warmer waters could compel the corals to seek cooler, deeper havens.

“When the water gets warmer, these creatures prefer to be deeper, but a coral doesn’t just walk down the mountain,” said Van der Kaaden.

Focus of the study 

Van der Kaaden conducted research on real reefs and using computational models. “In both cases, I tried to discover the spatial patterns in which the corals grow. With the Australian Great Barrier Reef, for example, this is very simple: you can even see their growth patterns from space.” 

Van der Kaaden’s exploration into the darkness wasn’t straightforward. She ventured into what she describes as a dark maze. 

“With cold-water corals, you have to recognize these patterns while walking around in a pitch-dark maze, so to speak, with only a small flashlight. And yet, using statistical techniques and video stills, we did manage to get an overall picture.” 

Ingenious adaptation 

The findings not only shed light on the regular patterns of reefs, ridges, and mountains formed by these corals but also on their ingenious adaptation to manipulate water currents for food.

“Over hundreds of thousands of years, the coral reefs form mountains that can grow higher than the Eiffel Tower. So, the corals get higher in the ocean, where there is more food, and those mountains also create water currents that transport the food to the mountain.”

Cold-blooded animals

The expectation is that if the water becomes too warm due to climate change, the corals will want to grow lower and colder. 

“A cold-blooded animal like a coral uses up too much energy in warmer water. But a coral is an animal that is attached to the bottom, so it can’t just move down the mountain,” said Van der Kaaden.

“It disperses through larvae, but for new corals, the food conditions on the flanks of a coral mountain are worse because of the specific flow patterns.”

Broader implications 

Despite the potential challenges posed by climate change, Van der Kaaden remains cautiously optimistic about the future of cold-water corals.

“Maybe these organisms are more resilient than we think, and if not, they might build new mountains or reefs in other places. But with this research, I do want to show that an organism’s response to climate change is not always easy to predict.”

“There are many complex processes that create unexpected obstacles or opportunities. We, as a society must take that into account when preparing for the effects of climate change.”

Image Credit: NOAA Fisheries

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