Abundance and relationship of bacteria with transparent exopolymer particles during the 1996 summer monsoon in the Arabian Sea

Bacterial abundance and production, numbers, sizes and concentrations of tr ansparent exopolymer particles (TEP) and total organic carbon (TOC) were me asured during the 1996 summer monsoon to understand the relationship betwee n TEP, the most labile particulate organic carbon, and bacteria. While high regional variability in the vertical distribution of TOC was discernible, TEP concentrations were high in surface waters at 18-20 degreesN along 64 d egreesE with concentrations well over 25 mg alginic acid equivalents l(-1) due to upwelling induced productivity. Their concentrations decreased with depth and were lower between 200 and 500 m. Bacterial concentrations were u p to 1.99 x 10(8) l(-1) in the surface waters and decreased by an order of magnitude or more at depths below 500 m. A better relationship has been fou nd between bacterial abundance and concentrations of TEP than between bacte ria and TOC. indicating that bacterial metabolism is fueled by availability of TEP in the Arabian Sea. Assuming a carbon assimilation of 33%, bacteria l carbon demand (BCD) is estimated to be 1.017 to 4.035 g C m(-2) d(-1) in the surface waters. The observed TEP concentrations appear to be sufficient in meeting the surface and subsurface BCD in the northern Arabian Sea.