Research at the ecosystem level for solar UV-B is barely beginning. Other factors, including those involved in climate change such as increasing CO 2 also interact with UV-B. Such reactions are not easily predicted, but are of obvious importance in both agriculture and in nonagricultural ecosystems. As a result, it is important to know how increased levels of exposure to solar UV-B radiation might affect the productivity of aquatic systems. In addition, the oceans play a key role with respect to global warming. Marine phytoplankton are a major sink for atmospheric carbon dioxide, and they have a decisive role in the development of future trends of carbon dioxide concentrations in the atmosphere.
Phytoplankton form the foundation of aquatic food webs.
Marine 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 nutrients, temperature, salinity and light availability, the high levels of exposure to solar UV-B radiation that normally occur within the tropics and subtropics 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. The position of the organisms in the euphotic zone is influenced by the action of wind and waves.