INTERPRETATION OF THE COASTAL ZONE COLOR SCANNER SIGNATURE OF THE ORINOCO RIVER PLUME

The Caribbean Sea is an area that traditionally has been considered ol igotrophic, even though the Orinoco River contributes large quantities of fresh water, nutrients, and other dissolved materials to this regi on during the wet boreal (fall) season. Little is known about the impa ct of this seasonal river plume, which extends from Venezuela to Puert o Rico shortly after maximum discharge. Here we present results from a study of the bio-optical characteristics of the Orinoco River plume d uring the rainy season. The objective was to determine whether the coa stal zone color scanner (CZCS) and the follow-on sea-viewing wide-fiel d-of-view sensor (SeaWiFS) satellite instrument can be used to assess the concentrations of substances in large river plumes. Recent in situ shipboard measurements were compared to values from representative hi storical CZCS images using established bio-optical models. Our goal wa s to deconvolve the signatures of colored dissolved organic carbon and phytoplankton pigments within satellite images of the Orinoco River p lume. We conclude that the models may be used for case II waters and t hat as much as 50% of the remotely sensed chlorophyll biomass within t he plume is an artifact due to the presence of dissolved organic carbo n. Dissolved organic carbon originates from a number of sources, inclu ding decay of dead organisms, humic materials from the soil, and gelbs toff.