There’s a saying among marine scientists: that we know more about the surface of the moon than we do about Earth’s own ocean. That was proven true again this April when a team of oceanographers announced the presence of a gigantic reef system at the mouth of the Amazon river. A reef covering 3,600 square miles (about the size of the island of Cyprus), stretching from the coast of French Guiana well into Northern Brazil, and between 30 and 120m deep. A reef that defies all we thought we knew about tropic coral reefs.
The Amazon river dumps one fifth of all the world’s fresh water runoff into the Atlantic Ocean, carrying with it enormous amounts of sediment. Normally, low salinity (fresh water) and sediment are death sentences to coral reefs. But this reef found a way to survive. Because fresh water is less dense than salt water, the sediment-filled outflow sits mostly on top of salty ocean water. The reef is in a deep, dark habitat a large portion of the time, but because of the seasonality of the Amazon’s flow and wind patterns in the area, the southern part of the reef gets sunlight for some parts of the year. Therefore, most of the photosynthesising coral is found in this southern reef area. The northern part, almost always in the dark, is instead dominated by sponges and coral-like red algae called rhodoliths.
This reef is such a surprise that even the researchers looking for it weren’t sure what they were going to find. They used dredges to pull up colourful reef fish, sponges, lobsters, tube worms, coral, and other organisms typically associated with tropical reefs. All were shocked and excited by what they were finding. No one could have expected such a large reef in such an inhospitable environment. The idea came from only one scientific paper published in the 70s suggesting such animal’s presence and reports of suspicious fisheries catches from the area. Mostly, the exploration was just a leap of faith.
No one has yet dived down to see the reef in person, however. The strong, unpredictable currents that allow the reef to filter-feed, but not to be smothered by sediment are too dangerous for the researchers to navigate just yet. They are still working on mapping the entire area with acoustic sampling and other passive methods.
It’s not all good news, though. This massive reef bed was in danger before it was even discovered. Besides the normal threats of warming waters, ocean acidification, pollution and overfishing, the Brazilian government has sold a significant portion of the area to oil companies for exploration and drilling, and oil is already being produced from some parts. Researchers are trying to get the area marked off as a Marine Protected Area, but it could be a long, hard battle ahead to protect this newly found treasure we know so very little about.
‘The Amazon Reef’ was written by Roya