Studies on the microzooplankton from the
central and eastern Arabian Sea

Mangesh Gauns, R. Mohanraju and M. Madhupratap

National Institute of Oceanography, Dona Paula, Goa 403 004, India

Numerical abundance and composition of microzooplankton in the upper 200 m were studied from the central and eastern Arabian Sea during three seasons. Protozoans, comprising of ciliates (loricates and aloricates), flagellates and sarcodines were dominant, ranging from 55 % to 91 %. Among metazoans, nauplii and copepodite stages were common. Microzooplankton abundance was generally higher in the upper 100 m water column during all the three seasons. The column values were from 69,000 m^-2 to 188,000 m^-2 (inter-monsoon), 7350 m^-2 to 56,350 m^-2 (winter monsoon) and 10,800 m-2 to 139,150 m' (summer monsoon). Seasonal averages were 700 l^-1, 130l^-1 and 310l^-1 respectively. A maximum of 5000 l^-1 was observed during summer at 5 m at a coastal station. Microzooplankton carbon in three different seasons ranged from a minimum of 4 ug C l^-1 during summer monsoon to a maximum of 36 ug Cl^-1 during inter-monsoon and was higher than that of mesozooplankton. Peaks in population observed during intermonsoon season, when phytoplankton productivity was low and relatively high bacterial abundance was observed, indicated a microbial loop.