A HYDROLOGICAL STUDY ON THE IMPACT OF SEASONAL VARIATIONS OF ENVIRONMENTAL PARAMETERS ON THE PLANKTON POPULATION OF ASHTAMUDI ESTUARY, KERALA

The Ashtamudi lake, a Ramsar site on the south west coast of Kerala located in Kollam district is the second largest among the thirty estuaries in Kerala. Thekkumbhagam, one among the eight creeks of Ashtamudi lake is a cradle for the post larvae of various fishes, clams, prawns, oysters that provides livelihood to thousands of people around the creek. The main objective of the present work is to remind the need for conservation of the biodiversity of this creek focusing on the planktonic resources that is the inevitable part of the aquatic biodiversity and its sustenance and to prevent its degradation to a mere sewage drain by thoughtless anthropogenic activities. The proper knowledge of planktons is essential as it forms a reliable tool for bio-monitoring and to maintain the sustainable fishery of the creek. The phytoplanktons collected from Thekkumbhagham creek from 2008-2010 were grouped under Chlorophyceae, Cyanophyceae, Dinoflagllates, Bacillariophyceae. Zooplankton consists of Protozoa, Cladocerans, Copepods, Rotifers, Crustacean larvae, Ostracods, Molluscs, Bryozoa. The various physico-chemical parameters analysed in the present investigation were air temperature, water temperature, pH, salinity, dissolved oxygen, carbon dioxide, transparency, biological oxygen demand and nutrients such as nitrite, nitrate, phosphate and silicate that exhibited a definite seasonal pattern. From the results it was clear that various physico-chemical characters were closely related to the availability of different types of plankton’s groups. Thus, the correlation analysis revealed the dependence of each plankton group with the hydrographical parameters of the Thekkumbhagam creek. Various types of pollution indicating algae were also found. From the present study a knowledge regarding the plankton abundance and its relationship with the the seasonal variations of the Thekkumbhagam creek will be helpful in planning and successful fishery management. In short the present study aims at providing useful data in the conservation of the economic, cultural, social, aesthetic, spiritual values and all other benefits of this creek there by focusing the mitigation of pollution affecting this creek.