Studies on the hydrobiology of river cauvery and its tributaries arasalar from Kumbakonam Region (Tamilnadu, India) with reference to zooplankton.

ABSTRACT

The present investigation was an attempt to examine the composition, abundance, frequency of occurrence and diversity of net zooplankton species inhabiting in river Cauvery and its tributaries Arasalar at Kumbakonam, Tamil Nadu, India. From the selected 6 stations of river Cauvery and its tributaries Arasalar water samples were collected at monthly intervals. Qualitative and quantitative analysis of zooplankton were carried out during the year 2010 January to December. In the river Cauvery 45 species of zooplankton were identified. Rotifera species was dominant (34.97%); followed by Cladocera (29.92%), Copepoda (18.27%), Protozoa (12.2%) and Ostracoda (8.72%). Throughout the study, six species of Protozoa, 13 species of Rotifera, 12 species of Cladocera, 11 species of Copepoda and two species of Ostacoda were identified in the river Cauvery. Similarly, in the river Arasalar 38 species of zooplankton were identified. Rotifera species was dominant (37.87%); followed by Cladocera (26.32%), Copepoda (19.74%), Protozoa (9.17%) and Ostracoda (6.43%). During the study period, 5 species of Protozoa, 12 species of Rotifera, 11 species of Cladocera, 9 species of Copepoda and one species of Ostacoda were identified in the river Arasalar. During the winter and summer season maximum zooplankton diversity was recorded which was mainly dominated by Rotifer population. High turbidity observed as a major factor which restricts growth of the planktonic population during monsoon season. Not all of the identified species were found in all six sites, thus indicating different types of pollution across the sites. There was no significant difference in the quantity of phytoplankton across the sites; however the quality differs as a result of the various stressors. These findings indicate that the effect of anthropogenic stressors, brewery effluent and refuse impact the water body, albeit minimally.