Chlorophyll ɑ and dissolved/suspended material effects on Secchi depth (Ds) were studied in the Gulf of Paria (Venezuela), during periods of low (June 1984 and May 1985) and high (October 1984) Orinoco River discharge (dry and rainy season, respectively). Correlations between ke (attenuation due to dissolved chlorophyll ɑ), kr (attenuation due to suspended and dissolved material) and Ds were negative and statistically significant, except the kr to Ds correlation in October. This suggests that such relations prevail during periods of low river discharge, but they are disrupted during high river input. In June, light in the upper 20 m decreased from Dragon's Mouth to the west and to the south inside the gulf. A similar pattern was observed in October 1984, but light decreased even faster in the vertical. In May, the light penetration keeps former spatial pattern but ¡t was more uniform and maximum light penetration was lowest. Even though the Orinoco River discharge produces a considerable decrease in water transparency in the Gulf of Paria -basically due to input of dissolved/suspended material during all seasons-, light supply is high enough to keep large phytoplankton populations, as suggested by chlorophyll ɑ data.