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article imageThe muddy waters of the Amazon have been hiding a huge coral reef

By Karen Graham     Apr 22, 2016 in Environment
An astonishing discovery has been made, and while a river's muddy waters have long hid it, there is a massive coral reef 600 miles in length at the mouth of the Amazon River in Brazil.
Of all the great rivers in the world, the Amazon River in South America is considered the largest based on the amount of water it discharges and is second in length only to the Nile River.
And the Amazon River is no mouse when it comes to its roar. The Amazon discharges about 209,000 cubic meters of water (55,000,000 USgals) per second. That comes to about 6,591 cubic kilometers per year, or about the total volume of the next seven largest independent rivers combined.
It is the waters at the mouth of the Amazon that have kept the coral reef in hiding all these years. The discharge from the river is some of the muddiest water in the world. The river enters the Atlantic Ocean through a broad estuary in north-eastern Brazil. This opening is huge, being 150 miles (240 kilometers) wide.
The brown color in the photo shows the muddy discharge from the mouth of the Amazon River.
The brown color in the photo shows the muddy discharge from the mouth of the Amazon River.
NASA/EOS satellite
Three million tons of sediment are washed into the Atlantic Ocean every day, and the discharge alters the salinity and color of the water for as far as 200 miles (322 kilometers) out to sea. The nutrients in the discharge support algae blooms for hundreds of miles from the shoreline.
It is because of the muddy sediment in the "Amazonian flume" that scientists believed the coral reefs would not exist in these waters because corals need sunlight and the proper salinity to thrive. So we can imagine how surprised scientists were to discover that a coral reef 600-miles long appears to be thriving below the freshwater outflow, reports the Guardian.
The Atlantic reports the reef sprawls out across the ocean floor for 3,600 square miles along the edge of the South American continental shelf, running from the southern tip of French Guiana to Brazil’s Maranhão State. The reef ranges from 30 to 120 meters deep.
Map of the Amazon showing the main structural traits of the reefs in the  Northern  Central and Sout...
Map of the Amazon showing the main structural traits of the reefs in the Northern, Central and Southern sectors of the reefs.
Patricia Yager et. al.
What is amazing about this story is that in the 1970s, researchers caught a few types of fish that indicated a reef was present under the muddy waters at the mouth of the river. The researchers even submitted a paper on their discovery, entitled Reef Fishes Over Sponge Bottoms Off the Mouth of the Amazon River. But it appears that no one took them seriously, and an opportunity was missed.
Co-author of the expedition report, Patricia Yager, a professor of oceanography and climate change at the University of Georgia, told the Atlantic, “I was flabbergasted, as were the rest of the 30 oceanographers. Traditionally, our understanding of reefs has focused on tropical shallow coral reefs which harbor biodiversity that rivals tropical rainforests."
But as it is with most of the world's coral reefs, this latest discovery is also endangered, but it's not what you might think. The Brazilian government has sold 80 blocks for oil exploration and drilling at the mouth of the Amazon and 20 of these are already producing oil, a few of them possibly being right on top of the reef.
"These [exploration] blocks will soon be producing oil in close proximity to the reefs, but the environmental baseline compiled by the companies and the Brazilian government is ... largely based on sparse museum specimens. Such large-scale industrial activities present a major environmental challenge,” said the study’s authors.
The paper detailing the expedition, "An extensive reef system at the Amazon River mouth," was published in the journal Science Advances on April 22, 2016.
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