Ocean ‘Deserts’ Grow

The region of the ocean known as “the desert of the sea” has expanded dramatically over the past decade, according to a new study.

Scientists looking at the color of the ocean from space have found that vast areas that were once green with plankton have been turning blue, as marine life becomes scarcer. If it’s linked to global warming, as they suspect, this could be another blow for the world’s fisheries.

Just as plants make up the base of the food web on land, tiny green phytoplankton in the ocean are a critical foodstuff for life in the oceans. And Jeff Polovina, at a National Marine Fisheries Service lab in Hawaii, has been watching by satellite as that greenery in the middle of the ocean is fading away.

“The regions that are showing the lowest amount of plant life, which [are] sometimes referred to as the biological deserts of the ocean, are growing at roughly 1 to 4 percent per year,” Polovina says.

One to 4 percent may not sound like all that much, but these regions are huge to begin with. So this marine desert has grown by 2.5 million square miles in the past decade. That’s an area the size of Texas every year. Polovina makes the analogy to deserts on land, creeping into more productive environments.

“We have the same thing here,” he says. “These less productive areas are replacing the slightly more productive areas of the ocean.”

Link to Global Warming

And it seems to be tied to global warming. Polovina’s study, published in Geophysical Research Letters, finds that the areas of low productivity are expanding in lockstep with increasing water temperatures. As surface temperatures warm, that prevents colder water from rising up from the depths. And that colder water carries the nutrients that would feed the algae.

Scientists studying climate change have predicted this kind of change. But the sea desert has been spreading 10 times faster than climate scientists predicted. So Polovina is a bit cautious