Phytoplankton production and chlorophyll distribution in the eastern and central Arabian Sea in 1994-1995

P. M. A. Bhattathiri, Aditi Pant*, Surekha Sawant, M. Gauns, S. G. P. Matondkar and R. Mohanraju

National Institute of Oceanography, Dona Paula, Goa 403 004, India
*National Chemical Laboratory, Pune 411 008, India

 Measurements of primary production, chlorophyll a, particulate organic carbon (POC) and nitrogen (PON) were carried out during the inter monsoon, winter monsoon and summer monsoon seasons of 1994-95 in the central and eastern Arabian Sea. The integrated production rate varied between 193-199, 337-643 and 770 mgCm^-2 d^-l respectively in the open ocean (along 64^oE) for the three seasons. The corresponding values in near coastal stations were 281-306, 200-807 and 440-1760 mgCm^-2 d^-1. Column chlorophyll a values for these seasons were between 8-17, 13-27 and 34-44 mgml in the open ocean and 11-12, 10-34 and 16 to 88 mgm^-2 for near coastal waters. A subsurface chl maximum (SCM) at ~4060 m was conspicuous during the intermonsoon period. The seasonal variation in productivity was consistent with the circulation patterns and associated nutrient levels. Phytoplankton and zooplankton (as carbon) contributed 10-22 % of POC. Estimated division rate of phytoplankton varied from 0.7 to 3 for different seasons and locations.