Variability in primary production as observed from moored sensors in the central Arabian Sea in 1995

Abstract

Carbon assimilation was calculated using surface irradiance and fluorescence data collected from moored sensors located in the Arabian Sea (15°30′N, 61°30′E), beginning the twelvemonth period in October 1994. The calculation uses an assumed quantum efficiency and independently estimated phytoplankton absorption coefficients. Fluorescence was calibrated to chlorophyll a. Estimated primary production (C assimilation) varied seasonally and was roughly correlated with chlorophyll a biomass. Variations in integral primary production estimated from the moored observations as a function of integral chlorophyll a are interpreted in terms of the variations in mixed layer depth and possible losses of chlorophyll a biomass. Deep mixed layers suggest lower chlorophyll a-specific production, and variations in chlorophyll a may indicate grazing losses. Seasonal variability in a measure of primary production is useful for establishing the relationship with environmental forcing in the Arabian Sea and in understanding the export of production to the deep sea.