Phytoplankton, single-celled photosynthesizing organisms in the world's oceans that can store as much carbon as all the plant life on the planet combined, are under threat from rising ocean temperatures, researchers say.
The tiny organisms, which are a major bulwark against climate change and the greenhouse effect as well as anchoring the marine food chain, also face serious threats from viruses that can wipe out phytoplankton blooms so massive they can be seen from space, scientists say.
Rising ocean temperatures have resulted in a 40 percent decrease in phytoplankton population since 1950, researchers at Canada's Dalhousie University say, which translates to a 1 percent drop annually between 1899 and 2008.
"It's very disturbing to think about the potential implications of a century-long decline of the base of the food chain," says marine lead author of a study published in the journal Nature.
The temperature increases cause changes in ocean circulation, affecting the amount of nutrients available for phytoplankton growth, especially in tropical oceans that making up almost 50 percent of he world's sea surface.
Less phytoplankton available to take up carbon will have an impact on climate change, researchers who conducted another study say.
"Climate regulation will ... be affected negatively by production decrease globally," says Guillem Chust of Azti-Techanlia, a marine and food research center in Spain, "because, as there will be less phytoplankton, absorption of CO2 from the atmosphere by the oceans will be lower, as plankton is responsible for half of the planet's photosynthetic activity.
"This in turn will reduce the ocean's capacity to regulate the climate," Chust says.
And if rising temperatures weren't threat enough, another study has found that phytoplankton are under increasing pressure from ocean viruses.
Researchers at the Weizmann Institute of Science in Israel have combined satellite data with field observations during ocean cruises to measure viral impacts on large phytoplankton blooms.
A large bloom covering more than 600 square miles of ocean surface can be almost entirely wiped out by viruses, they found.
In terms of carbon storage, such a loss equates to cutting down a comparable swathe of the Amazon rainforest, the researchers note.
And in addition to storing CO2, phytoplankton can affect how much heat the oceans of the world can absorb.
One question researchers have been unable to answer as of yet is whether climate change itself is responsible for an increase in such ocean viruses.
