Eutrophication Assessment Using Phytodiversity at the Land-Water Interface of Lake Anasagar of Ajmer

Abstract

Since most of the water, silt, nutrients, and organic inputs from the catchment areas must pass through theland-water interface before reaching the water body, the biota of this zone and the ecosystem processesoperating therein play a significant role in regulating water quality, biodiversity and productivity of inlandwaters. Therefore, this zone can be considered as a biological frame of the aquatic ecosystem. As the effectof pollutants coming from various anthropogenic activities and factors operating on land are morepronounced at the interface, the aquatic flora growing here may be indicative of trophic state of the waterbody. The present study deals with phytoplankton and macrophytes as a criterion for trophic evaluation ofAnasagar- a perennial freshwater lake of Ajmer which is being influenced by a number of anthropogenicactivities on its margin. Human settlements and construction activities in the catchment areas lead todeterioration of the water quality of the lake. The study indicates that rather than physico-chemicalcharacteristics used to classify wetlands under oligo- and eutrophic scales, Phytodiversity is a potent criterionfor trophic evaluation. As a major element of aquatic biota, the algal community often exhibits dramaticchanges in response to different types of pollutants. Hence, the diversity of algal component in the aquaticecosystem serves as a reliable index for biomonitoring of pollution load. Land-water interface is rich inalgal diversity, in all 123 algal species belonging to Cyanophyceae (41), Chlorophyceae (48),Bascillariophyceae (22) and Euglenophyceae (12) were recorded. On the basis of number of algal speciesbelonging to various groups, Nygaard Trophic State Indices were calculated which indicate hypereutrophicstatus of wetland. Wetland plants in land-water interface play an important role in nutrient dynamics. Thecontribution of some dominant macrophytes in nutrient enrichment at the land-water interface was alsoassessed. It was estimated that among the macrophyte species, Azolla pinnata and Trapa bispinosa contributedmaximum to the total nutrient inputs into the lake waters. If these macrophyte species are removed beforedecomposition Starts, nutrient enrichment of the lake may be checked to a large extent. Recently manyinitiatives have been taken to restore Lake Anasagar under National Lake Conservation Program throughinstallation of water treatment plant and by providing aeration in the water body. This will favourablyaffect the biological components including algal flora and macrophytes. Data on the physico-chemicalanalysis state that the water quality is still not improved because inputs of fertilizers and detergents havenot been checked so far.