Seasonal and spatial variability of zooplankton diversity in North Eastern Arabian Sea along the Maharashtra coast

The study focused on the variations in seasonal diversity of zooplankton between the polluted coastal environments of Mumbai and the comparatively less polluted coastal waters of Ratnagiri. The study was carried out from August 2014 to May 2017. Zooplankton was collected from hauls at 20 m and 40 m depth contours off Mumbai and Ratnagiri coast. The results indicated that Species Richness d, Shannon H and Simpson 1-λ at Mumbai stations were low compared to Ratnagiri stations. The values were higher in post-monsoon (POM) and pre-monsoon (PRM) than in monsoon (MON) season. Two-way ANOVA revealed a significant difference (P<0.05) for values of ‘d’, ‘H’ and 1-λ ’ between Mumbai and Ratnagiri. Post-Hoc Tukey test showed a significant difference (P<0.05) between values of ‘d’, ‘H’ and 1-λ ’ during MON and POM, MON and PRM. However, no significant difference (P>0.05) was observed between POM and PRM. Cluster analysis showed a 35% similarity in diversity between MON and the other two seasons. SIMPER analysis of similarity showed average dissimilarity of 44.77 between the diversity of Mumbai and Ratnagiri. The study indicated seasonal variations in the zooplankton diversity in coastal regions of Mumbai and Ratnagiri. The impact of pollution and anthropogenic activities could have reduced zooplankton diversity and abundance in the coastal environment of Mumbai compared to the less polluted waters of Ratnagiri.