Large rivers empty into oceans and create plumes, a swirling mass of fresh and salt water that signal breaks in coral reefs, which can’t live in fresh water. The Amazon River typifies this, and its plume creates a huge break in Atlantic reefs. At least, that’s what we thought.
A new study in Science Advances details a coral reef system discovered in the Amazon River plume, which is home to a wide variety of life and has some fascinating interconnected ecosystems as well. In the southern part of the plume, most of the reef is made of typical corals, which photosynthesize for food, because they have access to light.
But as you move north, the plume reduces the amount of available light underwater, and so there they reef consists largely of sponges and other creatures, which feed off nutrients washed out into the ocean by the river.
The study is pretty amazing and contributes a lot to our understanding of coral reefs. The variations in ecology based on access to light were particularly interesting. It reveals that microorganisms in the darker waters help to connect the river and reef environments.
But of course, it’s not all happy news. Like any other coral reef, this one is threatened by human activity. Increasing ocean acidity threatens the reefs, and there are also plans for offshore oil drilling in the area. Those plans can hopefully be stopped since it wasn’t apparent that there was a coral reef there, so maybe this discovery can forestall oil exploration there.
Ocean acidification and warming both have a devastating impact on coral reefs, as has been seen in other parts of the Atlantic especially, and this reef is no different. Maybe this discovery, and more research here, will help to spur more active attempts to reduce those impacts.