An international team of researchers discovered an enormous coral reef at the mouth of the Amazon River. In their study published on April 22 in the journal Science Advances, they state that this is a first since reef systems do not usually grow in plumes or areas where river freshwater mixes with seawater.

The researchers used a multibeam acoustic sampling of the ocean floor and analysed samples to locate the reef. According to Patricia Yager, an associate professor of marine sciences in UGA’s Franklin College of Arts and Sciences and principal investigator of the River-Ocean Continuum of the Amazon project, they found the most colourful animals they have seen in an expedition in the area.

The research team adds that the discovery of the reef system gives insight into the reef community, including any variation and changes that affect the wildlife harbouring in it. Moreover, the microorganisms living beneath the river plume may also reveal how the reef’s odd location affects them.

coral reef

The Amazon River meets the Atlantic Ocean and creates a plume where freshwater and salt water mix. Credit: Lance Willis

“The paper is not just about the reef itself, but about how the reef community changes as you travel north along the shelf break, in response to how much light it gets seasonally by the movement of the plume,” said Yager.

coral reef

The University of Georgia’s Patricia Yager, center, oversees ocean sampling equipment on board the RV Atlantis before it’s lowered into the Amazon River plume. Credit: Lance Willis

“In the far south, it gets more light exposure, so many of the animals are more typical reef corals and things that photosynthesize for food,” adds Yager. “But as you move north, many of those become less abundant, and the reef transitions to sponges and other reef builders that are likely growing on the food that the river plume delivers. So the two systems are intricately linked.”

However, like countless others, the reefs are also threatened. Yager points that the reef system is threatened by ocean acidification, offshore oil exploration, and ocean warming, just to name a few. The researchers suggest conservation efforts to save these.