Microdistribution of zooplankton in the neustonic realm of the eastern Arabian Sea during southwest monsoon

Abstract

During the southwest monsoon season of 1987, the zooplankton distributions in the neustonic realm (upper 50 cm) of the eastern Arabian Sea were studied and compared with those in the water column. The upper microlayer (upper 15 cm) had generally poor biomass and densities during day-time as compared to the lower microlayer (30-45 cm below). Diel variations were discernible in biomass and numerical abundance. There was nocturnal increase in biomass and density in both layers suggesting diel vertical migration, but the increase was relatively more in the upper layer than the layer below. Ostracods, amphipods, pteropods, mysids and megalopa larvae were significantly more abundant in the upper layer during night-time. Northern areas of West Coast of India had higher biomass and population density. Zooplankton abundance was more in the coastal belt as compared to the offshore waters