Scubaism

Water samples have confirmed the part of the ocean (the purple spot in the image) that has the least amount of life in it is in the south-east Pacific, near Easter Island.

Chlorophyll measurements show the patch contains roughly 10 times less chlorophyll than is found in most ocean waters, suggesting that this is one of the most life-poor systems on Earth. As such, says Patrick Raimbault of the University of the Mediterranean, in Marseille, France, UV rays could penetrate more than 100 metres below the surface.

In a sense, the patch is isolated from the global river and ocean circulation, which explains its lack of life. Being far away from the coast it does not benefit from continental run-off, and the thermohaline circulation – the “global conveyer belt” – which ferries ocean waters around the world, also mostly runs along the continental shelves.

Raimbault made another surprising discovery: the patch of the ocean that is poorest in life appears to be extremely rich in dissolved organic carbon.

He is currently teasing apart data in an attempt to explain the apparent contradiction, but believes it may be that the limited availability of nutrients such as nitrogen and phosphorus means the bacteria that would normally degrade the dissolved organic matter are not able to complete the task.