Jul 31, 2010
Ocean plant plankton in big decline
They play vital role in producing oxygen and removing carbon dioxide
These marine diatom cells are an important group of phytoplankton found in the oceans. A probable cause of the sharp decline in their numbers is global warming, which makes it hard for the plant plankton to get vital nutrients, researchers say. -- PHOTO: ASSOCIATED PRESS
They also are declining sharply.
Worldwide phytoplankton levels are down 40 per cent since the 1950s, according to a study published this week in the Nature journal.
The probable cause is global warming, which makes it hard for the plant plankton to get vital nutrients, researchers say.
The numbers are both staggering and disturbing, say the Canadian scientists who did the study and a top
'It's concerning because phytoplankton is the basic currency for everything going on in the ocean,' said
'It's almost like a recession... that has been going on for decades.'
Half a million datapoints dating to 1899 show that plant plankton levels in almost all the world's oceans started to drop in the 1950s. The biggest changes are in the Arctic, southern and equatorial
Dr Virginia Burkett, the chief climate change scientist for the US Geological Survey, said plankton numbers are worrisome and show problems that cannot be seen just by watching bigger and more charismatic species like dolphins or whales.
'These tiny species are indicating that large-scale changes in the ocean are affecting the primary productivity of the planet,' said Dr Burkett, who was not involved in the study.
When plant plankton numbers plummet, as they do during El Nino climate cycles, sea birds and marine mammals starve and die in huge numbers, experts said.
'Phytoplankton ultimately affects all of us in our daily lives,' said marine ecology researcher and lead author Daniel Boyce, also a professor at
'Phytoplankton... produce half of the oxygen we breathe, draw down surface carbon dioxide, and ultimately support all of our fisheries,' he said.
'An ocean with less phytoplankton will function differently.'
Plant plankton - some of it visible, some microscopic - help keep Earth cool. They take carbon dioxide, the key greenhouse gas, out of the air to keep the world from getting even warmer.
Professor Worm said that when the surface of the ocean gets warmer, the warm water at the top does not mix as easily with the cooler water below.
That makes it more difficult for the plant plankton, which are light and often live near the ocean surface, to get nutrients in deeper, cooler water.
It also matches other global warming trends, with the biggest effects at the poles and around the equator.
Previous plankton research has relied mostly on satellite data that goes back only to 1978. But Prof Worm and his colleagues used a low-tech method - disks devised by
The murkier the waters, the more plankton there is.
Prof Boyce says phytoplankton are similar to plants like grass and trees.
'Phytoplankton are basically like microscopic little plants. They require sunlight and nutrients in order to grow,' he told ABC News.
'Changes in their abundance will ultimately affect everything in the ecosystem, from tiny little zooplankton all the way up to fish and whales and ultimately humans,' he said.
ASSOCIATED PRESS
posted by Allan at
11:06 PM
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