Studies pertaining to the carbon fuation by marine phytoplankton in the Arabian sea off Mangalore wen camed out at monthly intervals from October 1995 to April 1996. Surface water samples were collected from 5 statiom located on the 10-50 m contour lines. This investigation revealed a distinct spatial variation for with less significant temporal variation both carbon fixation and chlorophyll a. Hper production rates wen recorded at 10 m dep both in terms of carbon fixation (mean value 8.8 mgC. m- . K') and chlorophyll a (mean value 8.8 mg. my. Hydrographical parameters such as salinity, ammonia, nitrate and phosphate recorded distinct spatial and temporal variations, while temperature and dissolved oxygen recorded distinct temporal variation only. 

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