ENVIS Technical Report: 25

Biological studies have been increasingly employed in monitoring water quality in lakes. (Zafar et al. 1981). Phytoplankton, zooplankton, macrophytic plants and fishes were used considerably in biomonitoring of lake ecosystems. Indian lentic ecosystems were investigated extensively for phytoplankton from mid 20 ^th century (Biswas ⁸⁴ 1949, Das and Srivastava ⁸⁵ 1959, Munnavar 1970, Zafar 1967, V.S Rao, 1977 Sharma et al. 1982). These studies show that the dominant phytoplankton and their seasonality are highly variable in different waterbodies according to their nutrient status, age, morphometry and other locational factors. However, in majority of the cases, phytoplankton is dominated by cyanobacteria followed by diatoms, chlorococcales and euglenoids (Zafar, 1986).

Zooplankton was investigated in Indian lentic ecosystems (Arunachalam ⁸⁶ et al. 1982, Suganan ⁸⁷ 1995). These studies reveal different groups of zooplankton have their own peak periods of density, which is also affected by local environmental conditions prevailing at the time.

Ali M. B ⁸⁸ et al. (1999) focused on toxic metal pollution, nutrient status of the lake and their magnification by algae and macrophytes in Lake Nainital, the sole source of drinking water for the local people and even to the majority of tourists. Water was found to be contaminated with metals like Cr, Cu, Fe, Mn, Ni, Pb and Zn. Concentration of some of them like Fe, Pb and Ni were higher than the recommended maximum permissible limits. Concentration of these metals was also found high in lake sediments. The level of metals amongst various components of lake varied considerably in different seasons. Plants and algae growing therein accumulated an appreciable amount of metals where water roots of Salix was more efficient than others in accumulation. Phytoremediation technology is proposed to restore water quality by harvesting submerged and floating biomass inhabiting littoral zone of the lake.

Aftab Alam ⁸⁹ et al., (1996) adopted both qualitative and quantitative estimation of plakton, the presence of plankton, and the dynamics and effects of varying dominant biota on the plankton population in four freshwater ponds receiving pollutants. Plakton were identified using standard monographs of Edmondson (1959) and Pennak (1980). ‘A’ pond, which received detergent pollutants, showed less plankton with thirteen genera of phytoplankton and seven genera of zooplankton, the dominant phytoplankton being Microcystis, Crucigenia tetrapedia, Nostoc, Selenestrum, Euglena, Phacus and certain diatom species and zooplankton such as Branchionus, Filinia, Hexarthra, Euchlanis, Moina, Cyclops and Diaptomus. The poor results for pond ‘A’ compared to ponds ‘B’ (24 species of phytoplankton and 15 species of zooplankton) and ‘D’ (30 species of phytoplankton and 17 species of zooplankton) was attributed to the influx of phosphorus into the waterbody by washing activities and dominance of certain planktivorous insects. Also, presence of certain pollution tolerant species of phytoplankton such as Oscillatoria, Scenedesmus, and Euglena indicated a high degree of organic pollution. The study concluded that both eutrophication and macrophytic infestation are responsible for plankton richness of ponds and the dominant biota affected other biota, bringing changes in the biotic composition with few others interfering directly with the biotic community.

Khan M.A ⁹⁰ (1996) discusses the comparison of the phytoplankton periodicity of a tropical upland reservoir in Nigeria (Liberty Dam, Jos Plateau) and a temperate type lake (L.Naranbagh) from the Kashmir Himalaya. Liberty Dam conformed to the ologotrophic-desmid plankton type whilst in L.Naranbagh, phytoplankton resembled the eutrophic chlorococcales-diatom plankton type. It was found that phytoplankton associations and periodicities in each of the two warm belt lakes were strongly driven by their respective local environments, including the marked seasonality of the climatic variables – rain, wind and solar radiation.

Muralidhar V.N ⁹¹ et al (2002) describes the physico-chemical characteristics of water, diversity and periodicity of phytoplankton in Gubbi tank, Tumkur city, Karnataka, India. Surface water samples were collected at an interval of 30 days for a period of one year. The physico-chemical parameters studied were within the permissible limits. Five classes and seventy two species represented the phytoplankton community namely Cyanophyceae, Chlorococcales, Bacillariophyceae , Euglenophyceae and Desmidiaceae. The density of phytoplankton shows that Bacillariophyceae dominated and constituted 36.36% of total phytoplankton population followed by Chlorococcales (25%), Cyanophyceae (25%) and Desmidiaceae (6.82%) and Euglenophyceae (6.82%). In the present study the maximum density of phytoplankton was recorded in May - 72760 Organisms/ Litre and minimum in September - 60099 Organisms / Litre. It was found that the density of the different groups of phytoplankton was more in the summer season than during rainy and winter seasons. Based on the results of Nygaard's and Palmer's algal indices the authors deduced that, the tank was eutrophic.

Shankar P Hosmani ⁹² (2002) adopted an integrated approach towards indicators of organic pollution in freshwaters. The advantage of each of the Biological indicators of water quality such as Saprobic index, Nyggard's index, Palmer's algal pollution index, biological index of pollution, inhibition threshold for dehydrogenase activity, Colilert defined substrate test, H2S strip test: Detection of faecal pollution in water.