ZOOPLANKTON DIVERSITY OF KOTTAKAYAL – A WETLAND IN SOUTH KERALA THAT IS UNDER THE THREAT OF SAND AND CLAY MINING

Zooplankton play multiple roles in an aquatic ecosystem. Nutrient recycling, energy flow, microbial remineralization, carbon cycling and maintenance of the population size of primary producers are some of the vital roles of zooplankton. Zooplankton are great indicators of the ecological status of a water body since their population dynamics changes with environmental changes. This study aims to identify the zooplankton population and its dynamics in a lake that was formerly paddy field. Kottakayal is a wetland lying near the Ittikara-Pallimon confluence. Sand and clay mining that is prevalent in this area has changed it into a water logged area. Zooplankton samples were collected from six sampling stations bimonthly for a period of two years from November 2015 to October 2017. Quantitative and qualitative analyses of the samples were made using standard protocols. Statistically significant seasonal variation in zooplankton population was noticed. Thirty eight species of zooplankton belonging to 7 different classes, 12 orders and 18 families were identified. Zooplankton abundance was maximum (119915±33053 nm-3) during monsoon season and minimum (55212±19637 nm-3) during pre-monsoon season. Rotifers were the dominant group of zooplankton in Kottakayal. Abundance of rotifers which are the chief food for fishes make this wetland suitable for practising aquaculture. Copepods were the second dominant zooplankton. Presence of species like Keratella, Brachionus, Monostyla, Lecane, Arcella and Difflugia indicated that Kottakayal was subjected to organic pollution.