These figures show monthly global ocean products derived using
GLI first continuous observation in April 2003. By combining
GLI products (chlorophyll-a
(A), sea-surface temperature
(B) and photosynthetically available radiation
(C)) and the ocean biological model, we can estimate the primary productivity of ocean phytoplankton
(D) that means the amount of
carbon per unit time and area that phytoplankton takes up and fixes as carbon dioxide in sea water by photosynthesis using sunlight and nutrients.
The primary productivity is remarkably high in mid-high latitude coastal regions where nutrient-rich water is supplied by the river and coastal upwelling caused by ocean currents along the shore. A high primary productivity region along the equator corresponds to an equatorial upwelling zone, and this region is a large nutrient input due to the upward flow caused by the east-west trade winds. As a result, phytoplankton concentrations are higher than in adjacent water, so primary productivity is high. At mid-high latitude regions, April is the phytoplankton bloom season (representing the greatest increase in phytoplankton of the year). The phytoplankton bloom in spring is caused by the increase in solar radiation from winter to spring. We suggest that high primary productivity near 30 to 40N in the Pacific and Atlantic Oceans resulted from the influence of a phytoplankton bloom in April.
Understanding the mechanisms of ocean primary productivity is very important for clarifying carbon cycles in the ocean relevant to global warming. It is also important for protecting and managing marine resources since phytoplankton plays a significant role in feeding habitats for marine commercial resources such as sardine and tuna through a marine food web.
July 8, 2003
