Quirks & Quarks

Amazon River hiding a massive reef ecosystem

One of the world's largest reef ecosystems has been hiding, undetected, under the muddy waters of the Amazon River, as it meets the Atlantic Ocean.

The muddy mouth of the Amazon has been covering an unexpected biological bounty

The muddy water of the Amazon's mouth obscure the reef ecosystem (Lance Willis)
The mouth of the Amazon River, where it meets the Atlantic Ocean, has been hiding what could be one of the world's largest reef ecosystems. River mouths aren't generally thought to be good environments for reefs, as the sediment carried by the river blocks light to photosynthetic organisms, and settles and buries anchored animals.

But an expedition led by Dr. Patricia Yager, an oceanographer and professor of Marine Sciences at the University of Georgia, in Athens, and her Brazilian colleagues, has found a reef system that stretches over thousands of square kilometres. The reef system includes a variety of organisms - corals, invertebrates, and fish - that survive in the low light conditions under the muddy outflow of the Amazon, while powerful currents are likely sweeping away the sediment that might otherwise bury them.

Like most reefs around the world, this newly discovered ecosystem is likely facing significant challenges from fishing, warming temperatures, ocean acidification, and offshore commercial development.

Related Links

Paper in Science Advances
- University of Georgia release
National Geographic story
Discovery News story