SESSION-3: Aquatic Biodiversity
PAPER-9: Ecological Survey of Loktak Lake with Particular 
Reference to Water Quality and Role of Phumdis
A. V. Gopalkrishna

Abstract:

An attempt has been made to study the water quality in respect of physico-chemical and microbiological characteristics and role of Phumdis in the Loktak Lake. Surface water samples were collected on monthly basis from 15 stations representing 5 zones, namely northern, western, eastern, middle and southern. Water quality was poor in the northern and southern zones of the lake as they have low dissolved oxygen, low pH, high CO 2 and high BOD. Water quality was healthier at the open water area than the Phumdi area. The total nitrogen content of the macrophyte species of Phumdis was observed as follows: Salvinia natans (1.8%) > Zizania latifolia (1.6%) > Capillipedium sp. (1.3) > Brachiaria mutica (1.2%) > Cyperus brevifolius (1.2%) > Echinochloa stagnina (1.0%) > Phragmites karka (1.0%) > Hedychium coranarium (0.94%). The present findings suggest that Phumdis are efficient in absorbing nutrients from the lake water. However, they are deteriorating water quality as they reduce the light penetration and accumulate organic matter in the lake ecosystem. Main reasons for rapid proliferation of the Phumdis are identified as heavy inflow of nutrients in the lake, transplantation of Phumdis for Phum fishing by the fisherman, construction of Ithai barrage for power generation and the wind action. Strategies for controlling proliferation of Phumdis and improvement of water quality of the lake are discussed.