Seasonal variation of copepod community structure in Chavara coast along the Southern Kerala, India

Abstract

Aim: To analyze whether the seasonally differing hydrographical parameters can alter chlorophyll a and zooplankton community distribution in Chavara coast during two different seasons. Methodology: The samples were collected from 10 m and 30 m locations from Chavara during November 2013 (Northeast Monsoon), May 2014 (Spring Intermonsoon). The collected zooplankton samples were analyzed in a stereo zoom microscope and copepods were identified to the species level. The relation between environmental parameters and zooplankton abundance was examined using statistical tools. Results: Water column was cool, nutrient rich and less oxygenated (subsurface) during November. Water column was characterized as warm, high saline and with less nutrients during May. These variations were closely linked with the increased cooling and continuation of weakened upwelling during November. Chlorophyll a was found two to five folds higher during northeast monsoon compared to the spring intermonsoon. Overall, 14 zooplankton groups were recorded in the present study of which copepods contributed more than 70% to the total zooplankton density. Zooplankton (3619.5 No.m-3) and copepod abundance (3212.8 No.m-3) was high in November. Non-metric Multidimensional Scaling (NMDS), Agglomerative Hierarchical Cluster Analysis (AHCA) on Bray-Curtis similarity clearly separated the samples of two clusters (30 m and 10 m) in two different seasons. Interpretation: The copepods showed more similarity within season and more heterogeneity between two seasons. Some copepod species showed positive relationship with the environmental variables.