- Extending from the southern tip of French Guiana to the Maranhão State of Brazil, the extensive sponge and coral reef system is 1,000-km (600-mile) long and unlike any tropical reef that has ever been studied.
- The scientists who made the discovery have published a study in the journal Science detailing their findings.
- The authors say that the unique reef system could provide insights into how coral ecosystems might respond to accelerating global warming.
Scientists have discovered a previously unknown reef ecosystem at the mouth of the Amazon River, and they’re warning that plans to drill for oil nearby could put the reef at risk.
Extending from the southern tip of French Guiana to the Maranhão State of Brazil, the extensive sponge and coral reef system is 1,000-km (600-mile) long and unlike any tropical reef that has ever been studied.
Rodrigo Moura of the Universidade Federal do Rio de Janeiro and a team of researchers from the U.S. and Brazil explored the region, about which very little is known, on three recent oceanographic cruises.
Moura and team identified large coralline algae and sponge beds as well as high levels of particulates, which they say are characteristics of the Amazon reef ecosystem that was shaped by different conditions from those that normally shape tropical coral reefs. The researchers have published a study in the journal Science detailing their findings.
By the time water flows the entire length of the Amazon River and empties out into the Atlantic Ocean, it is carrying a lot of mud, making the water nearly opaque. Fabiano Thompson of the Universidade Federal de Pernambuco in Recife, Brazil, one of the study’s co-authors, told Mongabay that the Amazon reef is unique in having developed in these turbid, nutrient-rich waters with low oxygen levels and no light.
There is high sponge and rhodolith cover, and extremely low coral cover, Thompson added.
“Chemosynthetic microbes are very important as primary producers instead of [the] photosynthetic organisms” that produce typical tropical reefs, he said. “The oceanographic conditions (biogeochemistry and microbiology) of this system are unique, not found in other places of the planet.”
The authors of the study warn that industrial-scale development of the Amazon shelf, which has been auctioned for oil drilling close to the reefs, could pose a major risk to the reef system. Major oil companies like BP, Total, Shell, Petrobras, and Brasoil are already drilling exploratory wells, Thompson said.
If the reef were harmed by these drilling activities, that would be unfortunate indeed, because the authors of the Science study say that the Amazon reef could provide insights into how coral ecosystems might respond to accelerating global warming.
Southern portions of the Amazon reef receive more sunlight throughout the year than northern parts of the reef, meaning that a range of responses to adverse conditions can be observed there.
“The reefs in the northern sector are no longer accumulating/producing calcium carbonate, only in the southern section,” Thompson said. “The [northern section’s] environmental conditions (no light, pH, sediment, nutrients) do not allow for biological carbonate precipitation. So the reefs in the southern sector may have higher resilience… In addition, because [the southern section reefs] are at high depths (90-100m depth), they may represent biodiversity reservoirs.”
Scientists are already studying other reefs that developed in extreme conditions that they say might actually survive the impacts of global warming. It was recently announced that as much as 93 percent of Australia’s Great Barrier Reef has experienced coral bleaching, due in part to warmer water temperatures. A widespread coral bleaching event is currently underway around the world.
- Moura, R.L., Paranhos, R.P., Leal, C.V., et. al. (2016). An extensive reef system at the Amazon River mouth. Science Advances. doi:e1501252