Enormous Coral Reef Discovered at Mouth of Amazon River

The extensive reef stretches 600 miles along the Brazil–French Guiana border. Continue reading →

At the Brazil–French Guiana border, where the Amazon River joins the Atlantic Ocean, the muddy waters have been hiding a spectacular secret.

A team of scientists reported that they discovered a coral reef there that stretches for 600 miles.

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The finding was completely unexpected. University of Georgia professor of marine sciences and oceanography Patricia Yager wanted to study how the Amazon River plume affects the ocean's absorption of carbon dioxide so she connected with Brazilian oceanographers, including senior scientist Rodrigo Moura, The Atlantic reported.

They were sharing the river vessel Atlantis when Moura mentioned looking for reefs, citing researchers who found fish in the late 1970s indicating such biodiversity might be under the water.

"I kind of chuckled when Rodrigo first approached me about looking for reefs. I mean, it's kind of dark, it's muddy - it's the Amazon River," Yager told The Atlantic's Robinson Meyer.

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Coral reefs aren't usually hard to spot: They tend to be located in clear tropical waters. But the Amazon River is so opaque in this area that the scientists needed to do a dredge, scooping up samples from the bottom habitat. With help from an old dredge shipped in from the University of Washington, the team hauled in fish, stars, sponges, and yes, coral. They were stunned.

While the biodiversity varies from north to south, the coral appears to cover more than 3,600 square miles of ocean floor between French Guiana and the Brazilian state Maranhão. The team just published their findings in the journal Science Advances. Next, they want to complete a map the reefs. Meyer called the coral another jewel in the Amazon River's crown.

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Given recent news that the Great Barrier reef coral is experiencing the worst bleaching ever, it was briefly heartening to know there's a bit of coral left that humans haven't decimated.

Yet hiding in plain sight hasn't helped the Amazon River coral. The scientists point out in their paper that, in the past decade, 80 exploratory blocks for oil drilling have been acquired and 20 are already producing right in the area they were studying. Protection, if it ever does come, may be too late to save this jewel from disappearing for good.