Phytoplankton is the basis of the extended aquatic food webs and any reductiori in biomass productivity due to increased levels of solar UV-B radiation (280-315 nm) is bound to have detrimental effects. In addition, the oceans play a key role with respect to global warning as marine phytoplankton are a major sink for atmospheric carbon dioxide. Phytoplankton are not uniformly distributed throughout the oceans of the world. The highest concentrations are found at high latitudes while, with the exception of upwelling areas on the continental shelves, the tropics and subtropics have 10 to 100 times lower concentrations. In addition to other factors solar UV-B radiation may play a role in phytoplankton distributions. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity. Here they are exposed to solar UV-B radiation which affects orientation and motility as well as photosynthesis, nitrogen uptake and other key physiological processes. Work in the Antarctic has shown a direct reduction in phytoplankton production due to ozone-related increases in UV-B.