SEA


Ocean Productivity


Ocean Biology

Microscopic green plants, called phytoplankton, form the lowest level of the marine food web and play important roles in many geochemical processes. Through photosynthesis, they convert dissolved carbon dioxide and other dissolved nutrients into organic and other compounds which initiate additional pathways in the biogeochemical cycles of elements such as carbon, nitrogen, phosphorus, oxygen and sulfur. Each cycle consists of processes that couple the terrestrial, atmospheric and oceanic domains and includes feedback mechanisms which modulate the interactions between the various cycle components.

With respect to "global change," the carbon cycle is of particular interest. Although ocean biota represent a small fraction of the total carbon in the system, their associated carbon fluxes are similar in magnitude to those linked with other, much larger, reservoirs. This indicates that phytoplankton are a very active component of the system.

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Ocean Color

Important features in the global pattern of phytoplankton are the high concentration (red and yellow) at high latitudes in the Northern Hemisphere, the relatively low concentration in the Southern Hemisphere, and the very low concentration (purple and blue) in mid-latitudes.

Global distribution of phytoplankton concentration is indicated by ocean color. Oceanographic data were collected by the Coastal Zone Color Scanner on NASA's Nimbus-7 satellite.

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Seasonal Baja Ocean Color

The colors in the lower part of this image are indicators of the abundance of phytoplankton, which serve as food for fish. Purples and blues depict low concentrations; greens and yellows depict moderate concentrations; and oranges and reds depict high concentrations. Land areas are shown in black.

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These images illustrate the marked seasonal variations in the distribution and abundance of phytoplankton in the Baja region. The most striking seasonal change in the Gulf is from low phytoplankton concentrations in the summer to high phytoplankton concentrations in the fall. This increase is due to upwelling induced by favorable northwest winds in the fall, which also results in phytoplankton abundance on the Pacific side of Baja. Satellite observations have provided the first globally observed patterns of ocean color, previously limited to scattered ship observations in well-traveled sea lanes.

Plans by NASA to continue ocean color research include the analysis of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) launched on the SeaStar mission in 1997 and the launch of the Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument on the EOS Terra and Aqua satellites.

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