Zooplankton distribution in coastal water of the North-Western Bay of Bengal, off Rushikulya estuary, east coast of India

In total, 186 species of holoplankton and 23 different types of meroplankton were encountered during this study. Zooplankton community was dominated by copepods represented by 112 species, belonging to 4 orders and 26 families Calanoida emerged as the most dominant order among the copepods being comprised of 68 species. It was followed by poicilostomatoids with 26 species, cyclopoids with 10 species and harpacticoida with 8 species. Paracalanus aculeatus emerged as the most dominant species during pre-monsoon season while, Acrocalanus longicornis was dominant in monsoon and A. gibber in the post-monsoon season. Other dominant copepods were Oithona sp., Miracia efferata, Acartia southwelli, Centropages tenuiremis, Paracalanus parvus, Acrocalanus gracilis and Acartia erythraea. Average zooplankton density ranged from 2387 org./10m(3) to 11659 org./10m(3). Zooplankton volume ranged from 0.65 ml/10m(3) in monsoon to 1.51 ml/10m(3) in post monsoon season. Despite high species abundance during premonsoon period, species diversity was maximum in monsoon. Species richness and dominance indices remained higher during post-monsoon whereas Pielou's evenness (J') was more in monsoon. Non-metric multidimensional scaling (MDS) ordinations based on Bray-Curtis similarities indicated that species composition was unequal during different months as there was no similarity above 40% level.