Spatio-temporal Study of Zooplankton Community in Mahanadi Estuary, Bay of Bengal

Spatio-temporal variation in zooplankton biomass, abundance, composition and hydrography were studied during 2009 in the Mahanadi estuarine complex. The estuarine system was strongly influenced by southwest monsoon and changed in the abiotic and biotic attribution system. There was an increasing trend of salinity observed from monsoon to post-monsoon, winter and followed by pre-monsoon which was peaked with 6.6 ± 5.37 psu, 10.5± 8.34 psu, 15.5 ± 4.38 psu and 24.10 ± 3.80 psu respectively. Dissolved oxygen was varied from 6.2 to 7.6 mg l -1 . However the pH was maintained a consistent trend and showed slightly alkaline in nature. Among 19 groups of zooplankton community, the preponderance of copepods (38 species) was observed as the major followed by mysids and chaetognaths. The dominant species were prevailed Paracalanus, parvus claus and Pontella andersoni sewell sp, which were conspicuous at river mouth. Whereas, Lucifer hanseni was observed at the river mouth during winter season only. Pearson correlation analysis indicated that total zooplankton population and biomass were positively correlated with PO4, NO2 and salinity (p< 0.01) and showed marked variations in density, biomass, species composition and relative abundance. This represented a complex ecosystem of Mahanadi estuary where many parameters were influenced together due to their cumulative impacts which result a major ecological driver of the estuarine system.