Ocean Losing Its Green

The oceans are the lifeblood of our planet and plankton its red blood cells. Those vital “red blood cells” have declined more than 40 percent since 1950 and the rate of decline is increasing due to climate change, scientists reported this week.

“Phytoplankton are a critical part of our planetary life support system. They produce half of the oxygen we breathe, draw down surface CO2, and ultimately support all of our fisheries,” said Boris Worm of Canada’s Dalhousie University and one of the world’s leading experts on the global oceans.

“An ocean with less phytoplankton will function differently,” said Worm, the co-author of a new study on plankton published this week in Nature.

Plankton are the equivalent of grass, trees and other plants that make land green, says study co-author Marlon Lewis, an oceanographer at Dalhousie. “It is frightening to realise we have lost nearly half of the ocean’s green plants,” Lewis told IPS.

“It looks like the rate of decline is increasing,” he said.

Climate change is warming the oceans about 0.2C per decade on average. This warmer water tends to stay on top because it is lighter and essentially sits on top of a layer of colder water. This layering, or stratification, is a problem for light-loving plankton because they can only live in the top 100 to 200 meters.

Eventually they run out of nutrients to feed on unless the cold, deeper waters mix with those near the surface. Ocean stratification has been widely observed in the past decade and is occurring in more and larger areas of the world’s oceans.

Phytoplankton or plankton are very small algae that live near the surface of oceans and form the basis of the marine food web. The unheralded plankton tribe may be the hardest- working group of organisms on the planet. Not only do they feed nearly everything living in the oceans, they absorb and sequester CO2 from the atmosphere, they also play a key role in cloud formation.

Plankton give off dimethyl sulfide, a chemical which floats to the ocean’s surface, evaporates, breaking down into sulfur compounds that become the nuclei around which clouds form.

Without plankton, the Earth would be a very different planet.

The researchers spent three years analysing and synthesising an unprecedented collection of historical and recent oceanographic data involving nearly half a million measurements of the transparency of sea water over the past 120 years. Previously, the “big picture” regarding plankton globally only went as far back as 1997 with the launch of special satellite

IPS