Diurnal variation of zooplankton in Malad Creek, Bombay

75-79Variation in zooplankton biomass and composition in relation to the prevailing hydrographical conditions was studied for 24 h in Malad Creek, Bombay, Maharashtra, India, which was highly polluted by sewage. The adverse effect of pollution was more during the ebb tide with relatively low values of salinity and zero values of dissolved oxygen. Zooplankton biomass varied from 0.01 to 13.2 ml. (100 m3) -1 [av. 3.4 ml. (100 m3) -1] during different tidal conditions. Zooplankton standing stock and total population were higher in night than in day collections. Abundance and diversity of zooplankton were directly correlated to the prevailing tide and pollution load. Copepods formed the predominant group followed by decapods, gastropods, chaetognaths and mysids. Variations in the incidence of different groups/species of zooplankton were discussed in detail