At approximately 9,500 square kilometers in size, a reef located at the mouth of the Amazon River has researchers amazed for a long list of reasons. The fact that this reef survives in waters, black enough in some spots to be mistaken for the damned soul of any culprit foolish enough to steal the final breath from an Amazon river dolphin, is definitely high up on that list.
That darkness is caused by a never-ending swirling mixture of both salt and fresh water muddied by sediment and being discharged at the staggering rate of 300,000 cubic meters every second where the Amazon meets the Atlantic ocean. That murk was one of the biggest challenges faced by a team comprised of Brazilian and American scientists aboard the Atlantis, an 83.5-meter-long (274 foot) research vessel owned by the U.S. Navy.
“I think that’s one of the remarkable findings of the study-that reefs can grow in places we don’t necessarily expect.” says American pelagic oceanographer Patricia Yager, an associate professor at the University of Georgia and director of the university’s Climate and Society Initiative. “The role of the Amazon River plume in structuring these ecosystems is really interesting and worth pursuing further, in my mind.”
Acting on the educated suspicions of the Federal University of Rio de Janeiro’s Rodrigo Moura, himself armed with a six page 1977 research paper that detailed the collection of fish specimens at the mouth of the Amazon usually found in a reef environment, the area in question was initially dredged in 2012 and then again in 2014. What was found astounded the researchers present, including Yager. “The animals we brought onboard the Atlantis were beautiful colours and shapes, just like you might imagine on a coral reef.”
The resulting study detailing the expedition’s findings was published in April 2016 at Science Advances. It describes how, in 2014, one 20 minute trawl recovered 30 species of reef sponges, and over 150 specimens in total. Overall, the study also collected 73 reef fish species, including Southern red snapper and angelfish. It also notes reef beds up to 300 meters (900 feet) in length, with some reaching a height of 30 meters (98 feet). “There are also a lot of coralline algae and rhodoliths that are responsible for a lot of the matrix. I’ve also heard the words “sponge reef” used, since a lot of the big animals we found were sponges,” summarizes Yager.
With only an estimated 10% of the Amazon reef mapped, the plans for future exploration are in the works. In Yager’s own talks with Moura, an expedition with an ROV (remotely operated vehicle) and rebreather-outfitted human divers have been discussed. “Conditions are difficult, though, because of the high currents and the deep depth. It will be a technological challenge,” she says.
And what would a story about the magnificence of Mother Nature be without the requisite potential storm cloud that is the threat from humankind in general? Climate change and fishing are major concerns, and the oil and gas industry already has exploration leases in place with the Brazilian government. Yager hopes that since the environmental impact assessments that were part of the leasing process were completed before the discovery of the reef that the leases should be reassessed, or at the very least put on hold until further study can be done.