Subsurface chlorophyll maxima in the north-western Bay of Bengal

Abstract

The depth profiles of phytoplankton pigments in the north-western Bay of Bengal are generally characterizEd. by a subsurface chlorophyll maximum. The occurrence of subsurface chlorophyll maxima is discussed in relation to other information on water column properties in the study area. The gradual deepening of the subsurface maximum from inshore to offshore waters coincides with the deepening of the thermocline. Significant correlation between the depth of the subsurface chlorophyll maximum and depth of thermocline suggests that the formation of the subsurface maximum is influencEd. by the presence of seasonal thermocline. Further the subsurface chlorophyll maximum is noticed within the depth ranges of ammonium maximum and nitracline, suggesting the regenerated nutrients may also extend a more important influence on the subsurface maxima. The presence of chlorophyll b and a high ratio of chlorophyll a/ phaeopigments in the subsurface layers substantiates the formation of the subsurface maximum due to growth of the photosynthetically active phytoplankton community.