EFFECTS OF LOW AND HIGH ORINOCO RIVER FLOW ON THE UNDERWATER LIGHT-FIELD OF THE EASTERN CARIBBEAN BASIN

In the spring and fall of 1988, two cruises were conducted in the Caribbean to examine the effects of the Orinoco River on the photochemistry of the eastern Caribbean. Detailed irradiance measurements were made at 29 stations using two scanning spectrophotometers; one measuring surface irradiance, the second measuring the underwater light field. The underwater light field data are presented and examined in this paper. The increased Orinoco River input in the rainy season produced significant changes in the underwater irradiance. This influence included a shift to longer wavelength in the light that penetrated deepest in the water column and an overall reduction in the total irradiance at any depth by approximately a factor of 2. Data will also be presented indicating the importance of accurate depth measurements collected in concern with the spectral irradiance data.