San José, Costa Rica, since 1956

What is the Thermal Dome?

According to Cindy Fernández, a marine biologist with conservation group MarViva, Costa Rica’s thermal convection dome is an underprotected and generally overlooked natural phenomenon that’s very important not only to the country’s biological wonders, but also to the economy. Over-fishing threatens to break down the food chain and damage the area.

The “dome” is a region north of Isla del Coco where a cold current with an unusually high concentration of nutrients strikes the underwater mountains of the Pacific Corridor and rises toward the surface, creating an ideal feeding ground for fish and other species, Fernández told The Tico Times. Such species include plankton and the animals that eat them: blue whales, in danger of extinction.

The phenomenon is seasonal, becoming more or less intense depending on the time of year. However, according to Eduardo Acosta, president of nonprofit Fundación EPIC (see separate story), Costa Rica’s dome is the only continuous upwelling in the world. The area is approximately 900 miles by 300 miles, he said.

“A really fast current comes at the bottom of the ocean, hits the corridor of mountains and banks up against that ridge and comes up to the top surface, and there it gets caught in a wind eddy… It keeps moving around, like a big bowl of jelly that sits out there, pure life,” Acosta told The Tico Times. “There are only five upwellings in the world, and only one is constant: this one.”

According to both Acosta and Fernández, the phenomenon was discovered not by scientists, but by fishermen who noticed the region was chock-full of fish.

Eventually, biologists, curious about the fishing activity there, used satellite imagery to determine what was going on approximately nine years ago, Acosta said.

Fernández said little is known about the dome, since scientists have never conducted a comprehensive study of the region, but one thing’s for sure: it’s an area worth protecting.

“It has biological importance, and in the end, importance for humans,” she said. “It’s a very significant, unique zone – fishing in our country depends a great deal on the thermal dome. If (foreign fishing companies) are constantly extracting the product, it will affect regional fishermen… Generally, what fishermen take out are big fish such as sharks and tuna, so all the other (animals) are affected. If we take something out, the whole chain stops functioning.”


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