Estimates of Indian Ocean productivity using natural fluorescence

Abstract

Measurements of the vertical distribution of phytoplankton natural fluorescence in the equatorial Indian Ocean produced estimates of oceanic productivity ranging from 70 to 150 mg C-m' '.day-'. Vertical profiles of the water column revealed the presence of a distinct chlorophyll maximum which forms at or near the top of the thermocline at almost every station. Localized upwelling was observed in the vicinity of atolls which appears to be responsible for an island mass effect that may add to downstream oceanic productivity. There were no significant differences along an east and northward oceanic transect from 63" 20' E to 88" 56' E longitude. The estimates agree with previously reported production estimates for the Indian Ocean reinforcing the image of low and variable rates of production throughout the deep oceanic basin punctuated by localized islandinduced upwellings.