Seasonal succession in mesozooplankton community in the tropical coastal waters: A study at Kalpakkam, southeast coast of India, Bay of Bengal

Abstract

Spatio-temporal variations in mesozooplankton diversity and abundance were assessed over 3 years at 6 coastal stations off Kalpakkam, along the Tamil Nadu coast. Samples were collected seasonally for eight consecutive seasons. Spatial variations were observed with respect to two transects, one at 0.5 km and the other at 5 km inside the sea, with three stations in each transect covering ~ 20 km stretch of the coastline. The results showed relatively high zooplankton diversity and density during the pre- and post-monsoon seasons compared to the monsoon season. Zooplankton density ranged from  0.54–6.10×10⁴ individuals per 10 m³ in the nearshore waters and 0.44–4.83×10⁴ individuals per 10 m³ in the offshore waters. A total of 183 taxa were recorded. Out of which, 97 were copepods, 47 Non-Copepod Holoplankton (NCH), and 39 meroplankton. As expected, the copepod group dominated the zooplankton community, belonging to 25 families and 39 genera. Copepodite stages were recorded for 12 copepod taxa. A relatively low number of species was recorded during the monsoon seasons. Seasonally, copepods were found to contribute 26–65 % of the total zooplankton community, followed by NCH (22–69 %), meroplankton (2–19 %), and copepodite (1–5 %). Zooplankton species abundance showed a strong positive correlation with salinity and a negative correlation with turbidity. Non-metric Multidimensional Scaling (nMDS) and similarity percentage (SIMPER) analyses indicated an almost uniform distribution of zooplankton communities across the spatio-temporal scale.