Dynamics of weather fueled by plankton.

Dynamics of weather fueled by plankton 

Microscopic ocean plants called phytoplankton may exert an important influence on Indian monsoons and other weather patterns across the globe, reports a team of oceanographers from Canada and India.

Shubha Sathyendranath at Dalhousie University in Halifax, Nova Scotia, and her colleagues reached that conclusion after examining the role of phytoplankton in the Arabian Sea, which lies west of India. The researchers used statellite measurements and a computer model to determine whether these one-celled plants have a significant effect on sea-surface temperatures in the region. In the Jan. 3 NATURE, they report that the "distribution of phytoplankton exerts a controlling influence on the seasonal evolution of sea-surface temperatures."

Phytoplankton contain photosynthetic pigments such as chlorophyll, which absorb solar energy, warming the surrounding water.

Computer simulations by Sathyendranath's group revealed that phytoplankton could significantly warm the surface of the Arabian Sea, boosting temperatures by as much as 4 [degrees] C during summer months.

Because the pattern of ocean temperatures in the tropics influences the development of storms, fluctuations in phytoplankton concentrations might affect the location or strength of Indian monsoons. The researchers suggest that forecasters might use satellite measurements of oceanic chlorophyll concentrations to improve the accuracy of seasonal weather predictions for the tropics.

The new findings fit with other recent research exploring the role of phytoplankton. In a study of the tropical Pacific, Marlon R. Lewis of Dalhousie and his colleagues found that the tiny plants greatly reduce the water's transparency and could account for geographic variations in sea-surface temperature patterns. They suggest in the Oct. 11, 1990 NATURE that sporadic phytoplankton "blooms" may play a role in starting El Nino-Southern Oscillations, which wreak havoc on global weather patterns.

Some researchers have proposed that phytoplankton partially control the world's climate because they emit a sulfur compound that stimulates the "seeding" of cloud particles (SN: 12/5/87, p. 362). In general, Lewis says, scientists are developing a greater appreciation for the importance of these plants. "Biological organisms are not just passive and at the mercy of the climate and their physical environment," he says, "but in fact can carry out fairly significant modifications of the physical climate system."