Ocean Color and Chlorophyll

Ocean color imagery is produced from satellites in near-earth orbit. These satellites use optical scanners in several bands (colors) to produce digital images. These images are in turn blended to yield a product resembling a photographic image. Offshore oceanic waters with little content of suspended or dissolved materials appear dark blue. Blooms of phytoplankton (microscopic algea and bacteria) can impart green, brown, red or even white coloration. River plumes near the coast often appear reddish/brown due to their high content of suspended sediment. In contrast, large river plumes offshore have lost most of their load of suspended sediment but carry large concentrations of dissolved organic matter that darken the image considerably (think tea or coffee). In our region, the Orinoco River plume extends seasonally throughout the eastern Caribbean and is readily apparent in ocean color imagery in the late fall. Local fishermen in the Antilles refer to it as "black water".'

Chlorophyll is the green photosynthetic pigment in all plants. Phytoplankton are the microscopic photosynthetic organisms that sustain the oceanic food chain. Although we may think of them as green, after all, they contain chlorophyll, most are in fact golden brown, red or yellow. Ocean color imagery, as explained above, is recorded in several discreet bands (colors). Imagery of phytoplankton distribution is generally based on the chlorophyll content of the surface water. This information is extracted from the various bands using previously developed mathematical formulas known as algorithms. Chlorophyll imagery is not however displayed as green colors but rather in "false color". Usually a rainbow pattern is used with high chlorophyll represented as red and low as blue.