P. antarctica, single-celled algae that can grow in lower light conditions, tend to populate more deeply mixed waters. P. antarctica and diatoms differ geochemically, too, in that diatoms don't take up carbon dioxide as efficiently as P. antarctica . In fact, the ratio of carbon uptake to phosphorus uptake for P. antarctica is nearly twice as high as that for diatoms. SeaWiFS image of the Southern Hemisphere, September 1997 to August 1998. Red and yellow pixels show where there are high concentrations of phytoplankton, while dark blues and purple show very low concentrations of the microscopic plants.
Phytoplankton typically thrive at or near the sea surface where sunlight is most abundant.
But since they can't swim, they are extremely sensitive to ocean dynamics. Climate models indicate that over the next half century, increased precipitation in the Southern Ocean could have a significant effect on ocean dynamics, particularly ocean surface stratification. Ocean water typically consists of layers that differ in density, temperature, and salinity. The surface layer stratifies, or divides into layers, in response to atmospheric conditions. Stratification increases when surface waters warm, or when precipitation adds freshwater to the surface layer.