plankton

diatoms colourful — A number of marine diatom cells (Pleurosigma), which are an important group of phytoplankton in the oceans.
Credit: Michael Stringer

“There’s a synergistic effect between increased ocean acidity and natural light”

“It’s clear we are conducting a giant experiment on the planet and we don’t know what we are doing.”

By Stephen Leahy

UXBRIDGE, Canada, May 8, 2012 (IPS)

Without major reductions in the use of fossil fuels, sunlight will kill an unknown number of ocean phytoplankton, the planet’s most important organism, a new study reports this week.

Not only are phytoplankton, also known as marine algae, a vital component in the ocean’s food chain, they generate at least half of the oxygen we breathe.

In the not so distant future, sunlight, the very source of life for phytoplankton, will likely begin to kill them because of the ocean’s increasing acidity, researchers from China and Germany have learned.

“There’s a synergistic effect between increased ocean acidity and natural light,” says Ulf Riebesell of the Helmholtz Centre for Ocean Research in Kiel, Germany.

Riebesell added that it was also possible “phytoplankton could adapt”.

Researchers were surprised to discover that diatoms, one of the most important and abundant types of phytoplankton, fared very badly during shipboard experiments conducted by co-author Kunshan Gao, from the State Key Laboratory of Marine Environmental Science at Xiamen University, Xiamen China.

Previous experiments in labs like Riebesell’s found that diatoms actually did better in high-acid seawater, unlike most other shell- forming plankton. Burning fossil fuels has made the oceans about 30 percent more acidic researchers discovered less than 10 years ago. Oceans absorb one third of the carbon dioxide (CO2) emitted from using fossil fuels.

The good news is this has slowed the rate of global warming. The bad news is oceans are now more acidic and it will get worse as more CO2 is emitted. This is basic, well-understood ocean chemistry. Continue reading →

Bruun2_highres — A number of marine diatom cells

By Stephen Leahy

VIENNA, Jul 31, 2010 IPS

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 Canadas Dalhousie University and one of the worlds 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 oceans’ green plants,” Lewis told IPS.

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

natlantic plankton sml — A large phytoplankton bloom in the Northeast Atlantic -NASA Earth Observatory Collection.

[See also my series of articles on ocean acidification]

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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. Continue reading →