~ 192 ~ International Journal of Fisheries and Aquatic Studies 2015; 2(3): 192-197 ISSN: 2347-5129 IJFAS 2015; 2(3): 192-197 - © 2015 IJFAS www.fisheriesjournal.com Received: 14-11-2014 Accepted: 18-12-2014 Ranju Radhakrishnan Marine Biology Dept., Cochin University, Kochi-682016, Kerala, India Jayaprakas,V. Institute of Marine Science & Technology, Amity University, Sector 125, Noida, UP, India. Correspondence: Jayaprakas V Institute of Marine Science & Technology, Amity University, Sector 125, Noida, UP, India. Free living protozoans as bioindicators in Vembanad lake, Kerala, India, an important Ramsar site Ranju Radhakrishnan and Jayaprakas V. Abstract The use of the free living protozoan communities has benefited in perfectly characterizing and monitoring the prevailing environmental conditions of aquatic habitats that are typically found at marginal freshwater regions. A particular community of organism may be useful as an environmental indicator due to many reasons. Some may have sensitivity to low levels of anthropogenic contaminants, yet some others may tolerate and survive in the hardy and extreme conditions, and others also may react quickly to change in environment. Thus they tend to become a unique biotic tool to understand the ecological status of an aquatic habitat. Vembanad Lake and its adjacent kol lands has acclaimed international recognition as a Ramsar site. This lake is a biological niche of a multitude of organisms and it is intricately woven with the lives of the resident communities of its banks. The lake has also been facing severe environmental crisis during the last 3 decades due to anthropogenic influences. Presently, 19 species of free-living protozoans have been identified and characterized from this lake. A total of 15 testacid rhizopods belonging to 2 orders, 6 families and 9 genera were recorded. And the ciliates of 3 orders, 3 families were recorded. Among the testaceous rhizopods 1species from Arcellidae family, 5 from Centropyxidae, 1 species from Nebelidae, 6 from Difflugidae belonging to the Class Lobosea and 2 species from the Class Filosea belonging to Cyphoderiidae and Euglyphidae families were identified. Some of these freeliving forms have given certain insights of the prevailing ecological conditions of this lake thus acting as perfect Bioindicators. Euglypha tuberculata reported in the present study is a species of wide tolerance and survives in diverse habitats. Similarly Cryptodifflugia oviformis which was reported for the first time in India in this study prefers dryer environments. Due to its small size, this species mainly feeds on bacteria and yeasts, their high abundance explains active decomposition process in the area. The diversity of the free-living ciliates in the study area included species belonging to 3 genera namely Euplotes, Tachysoma and Coleps and they were pollution indicators possessing the property of heavy metal uptake. The water quality analysis and heavy metal analysis also proved the waters of the lake polluted with heavy metal concentrations. Thus the present study draws our attention to the possibility of using these dominant ciliate species for bioremediation of aquatic pollutants in this lake. Thus these freshwater free living protozoans serve as good bioindicators reflecting the natural ecological conditions prevailing in the Vembanad Lake. They can also be effective bioremediation tools that can be applied to solve the heavy metal pollution crisis of the lake. Keywords: Marine ornamental fish, Parasites, Caligus, Aquaculture, Fish diseases. 1. Introduction Lakes hold nearly 90% of the liquid surface freshwater on earth and are major regulators in global carbon, nitrogen and phosphorus cycles. They are important reservoirs for freshwater, excellent purifiers of the terrestrial wastes and zones for aquifer recharge that provide critical habitat to a number of fauna and flora (Laurie Duker and Lisa Borre, 2001) [1] . The Vembanad lake in Kerala, India fosters high biological diversity and has been providing hydrological and ecological services thus supporting livelihoods of a huge rural population. It is a designated Ramsar site since 2002. The Lake which is spread across in three districts of Kerala – Ernakulam, Kottayam and Alappuzha – has a total surface area of 36,500 ha. It is a complex system of backwaters, marshes, lagoons, mangrove forests, reclaimed land and an intricate network of natural and manmade canals. Unique cultural traditions, water centered social institutions and lifestyles have evolved around the wetlands over time. The evolutionary history of this lake shows that this lake plays an important role in the ecology and economy of the south-west coast of India. The lake is presently undergoing severe environmental crisis due to the unregulated anthropogenic activities that are disrupting the natural balance of this rich