Phytoplankton bloom monitoring in the offshore water of northern Arabian Sea using IRS-P4 OCM satellite data

Abstract

IRS-P4 Ocean Color Monitor (OCM) satellite data were analyzed to generate chlorophyll-a images during the winter monsoon period to understand the high productivity and algal bloom patches as observed in the chlorophyll images. The winter bloom in the northern Arabian Sea is the most intense because of the nutrient build-up prior to its onset is so large and the mixed layer detrains earlier than in the other regions, which in turn triggers the surface productivity. A few bloom forming features are identified in the OCM derived chlorophyll images in nine days of overpasses (February, 15 to March 4, 2000) of the late winter monsoon period and their movement mechanism on temporal scale has been studied. Very high chlorophyll concentration in the range of 2.0 to 5.0 mg/m³ have been observed around the bloom forming waters in satellite images. The peak chlorophyll concentration observed in the center of patches reduces towards their peripheral water. The curly bloom forming features initiates with moderate chlorophyll concentration (0.6-1.0 mg/m³), grows to high concentration (1.0-2.0 mg/m³) and diminishes with low concentration (<0.6 mg/m³) ranges, lasting for about two-three weeks duration.