Distribution, Diversity of Mesozooplankton with Special Emphasis on Copepods from the Coastal Waters of South Andaman Islands

The present study provides the scenario of density and diversity of mesozooplankton from the study areas viz. Chidiyatapu, Burmanallah, Junglighat and Chatham from Port Blair region of South Andaman during inter-monsoon period (Dec 2022 to Feb 2023). Zooplankton density ranged from 374.5 to 588.6 no/m³ and showed variation across the stations (p <0.05; one-way ANOVA) and negatively linked with chlorophyll content. Mesozooplankton community comprised 19 different taxa belonged to 6 phyla viz. Cnidaria, Chordata, Chaetognatha, Arthropoda, Annelida and Mollusca. A large portion of mesozooplankton abundance was contributed by copepods (56.5±11.8%) followed by decapod larvae, invertebrate eggs and amphipods. Copepods were represented by 39 species belonged to 4 orders viz. Calanoida, Cyclopoida, Harpacticoida and Poecilostomatoida. Copepod fauna was dominated by widely distributed 12 copepod species viz. Acartia erythraea, Canthocalanus pauper, Calanopia minor, Calanopia elliptica, Temora discaudata, Paracalanus aculeatus, Paracalanus parvus, Acrocalanus gibber, Centropages orsinii, Labidocera acuta, Coryceaus sp., Oncaea sp. The number of copepod species and the number of individuals were significantly varied between the stations (p< 0.05; one-way Anova). The density of zooplankton was negatively linked with chlorophyll a content indicating grazing pressure by zooplankton. CCA analysis depicts that pH and chlorophyll a are the major variables influencing zooplankton assemblages in this area. Shannon diversity index indicated Burmanallah (st.1) and Chidiyatapu (st.2) were rich in copepod species with higher diversity (H’=2.51 ±0.24) while Junglighat (st.3) and Chatham area (st.4) with abundance of carnivorous gelatinous zooplankton such as chaetognathas, hydromedusae siphonophores, ctenophores and salps that feed on zooplankton including copepods showed low diversity (H’=2.18±0.05). Low evenness (J’= 0.68) in copepod species distribution at st.1 could be due to the dominance of few copepod species such as Oncaea and Corycaeus sp. in this area. The cluster analysis showed the species forming the groups depending on the type of distribution and abundance.