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Story highlights
- A 600 mile-long coral reef was found at the mouth of the Amazon River
- Many of the reef's fish are carnivorous
(CNN)The Amazon River, known for its array of wildlife from pink dolphins to flesh-eating piranhas, has revealed a new treasure -- a massive coral reef that stretches for some 600 miles, scientists say.
A team of scientists from Brazil and the United States discovered the reef in the muddy waters at the mouth of the Amazon, according to a report published in the journal Science on Friday.
The reef system spans 3,600-square miles along the ocean floor, stretching from French Guiana to Brazil's Maranhao state along the edge of South America's continental shelf.
The finding is surprising because large rivers normally create gaps in reef distribution due to unfavorable conditions such as salinity, pH and light penetration. However, this coral reef system seems to be healthy, according to the report.
American and Brazilian researchers collected this sponge sample as well.
The carbonate structure, which functions as a waterway passage for fish and other marine life, is home to a big colony of sponges and other creatures that thrive in low-light waters. The study recorded 73 reef fish species, many of them carnivorous.
An international team of scientists from the University of Georgia and the Federal University of Rio de Janeiro was on an expedition to learn more about Amazon River plumes when it made the discovery. Plumes are where the river's freshwater mixes with the ocean's saltwater.
"Our expedition into the Brazil Exclusive Economic Zone was primarily focused on sampling the mouth of the Amazon," Patricia Yager, an associate professor with the University of Georgia and principal investigator of the project, said in a statement.
The Amazon River meets the Atlantic Ocean, creating a plume where freshwater and salt water mix.
However, Yager also wanted to explore the premise of a scientific article from the 1970s that mentioned a scientist capturing reef fish along the continental shelf, which suggested a coral reef may be somewhere in the area.
The search proved fruitful. "We brought up the most amazing and colorful animals I had ever seen on an expedition," Yager said.
The paper details the reef and the variations in its fish, sponges and other marine life along the shelf due to the amount of light in the area and the plume's movement. The southern part of the reef, which gets more light, has a wide spectrum of reef critters. Further north, as the light diminishes, the wildlife transitions to creatures like sponges.
Along with the discovery of the reef, researchers also found evidence suggesting this Amazonian jewel may already be threatened.
"From ocean acidification and ocean warming to plans for offshore oil exploration right on top of these new discoveries, the whole system is at risk from human impacts," Yager said.
News of the extensive reef structure comes as various coral reef systems continue to suffer around the world because of warmer water temperatures and other factors, according to NOAA.
Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
There are 'winners' and 'losers' among corals as they respond to the accumulating impacts of climate change.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
There are variations in the appearance of severely bleached corals. Here, the coral displays pink fluorescing tissue signalling heat stress.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
The different color morphs of Acropora millepora, each exhibiting a bleaching response during mass coral bleaching event.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
A bleached Acropora colony.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
A severely bleached branching coral amongst the minimally bleached boulder coral.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
Dramatic coral bleaching, seen in Australia's Great Barrier Reef from March 2016.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
Some of the bleaching of reefs in the northern section has been described as "extreme."
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached."
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
"At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
A photo taken on September 22, 2014, shows bleached coral on the Reef, a key Australian tourist attraction.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached."
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival.
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Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching
The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016.
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A recent report from ARC Centre of Excellence for Coral Reef Studies showed that 90% of the Great Barrier Reef off the coast of Australia is suffering from coral bleaching, which is caused by changes in ocean conditions such as temperature, light or nutrition.
This bleaching happens as algae and other organisms living on the structure leave, depriving the coral of its major food source and causing it to turn white.
Coral bleaching is considered "the most widespread and conspicuous impact of climate change," according to the U.N.'s Intergovernmental Panel on Climate Change.