Aquatic macrophytes play an important role in the structural and functional aspects of aquatic ecosystems by altering water movement regimes, providing shelter to fish and aquatic invertebrates, serving as a food source, and altering water quality by regulating oxygen balance, nutrient cycles, and accumulating heavy metals. The ability to hyperaccumulate heavy metals makes them interesting research candidates, especially for the treatment of industrial effluents and sewage waste water. The use of aquatic macrophytes, such as Azolla with hyper accumulating ability is known to be an environmentally friendly option to restore polluted aquatic resources. The present review highlights the phytoaccumulation potential of macrophytes with emphasis on utilization of Azolla as a promising candidate for phytoremediation. The impact of uptake of heavy metals on morphology and metabolic processes of Azolla has also been discussed for a better understanding and utilization of this symbiotic association in the field of phytoremediation.

The present study deals with the limnobiotic status of three selected lakes of Himachal Pradesh using physicochemical and biological parameters (especially phytoplankton and zooplankton) over a period of 2 years. One hundred forty-eight species belonging to nine groups of phytoplankton and 79 species belonging to five groups of zooplankton were identified from the lakes. Trophic level and the pollution status of the lakes were assessed upon the basis of Shannon diversity index (H'), species richness index (S), and physicochemical parameters. Plankton population size was correlated with biotic and abiotic parameters (pH, alkalinity, temperature, dissolved oxygen, transparency, phosphate, chloride, and nitrate). The present investigation revealed that the distribution of plankton species depended upon the physicochemical parameters of the environment. Based on water quality standards given by the Central Pollution Control Board, the water quality was between "A-B" at Prashar wetland, "C-D" at Kuntbhyog Lake, and "D-E" at Rewalsar Lake. The results from the present study indicated that the potential of planktons as bioindicators of trophic status is very high.

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Discharge of untreated domestic and industrial wastewater into aquatic bodies is posing a serious eutrophication threat, leading to a slow degradation of the water resources. A number of physical, chemical and biological methods have been developed for the treatment of wastewaters; among these, the use of microalgae is considered as a more eco-friendly and economical approaches. Microalgae are versatile organisms which perform multiple roles in the environment-bioremediation of wastewater, gleaning of excess nutrients and in turn, generate valuable biomass which finds applications in the food, biofuel and pharmaceutical industries. They are currently being utilized to reduce the high nutrient load (especially N and P) from wastewaters, which fulfill the growth requirements of microalgae, making it a suitable cultivation medium for biomass production. The present review represents a comprehensive compilation of reports on microalgal diversity of wastewaters, followed by a critical overview of their utilization, suitability and potential in bioremediation vis-a-vis biomass production. This review also emphasizes the superiority of polyalgal and consortial approaches in wastewater treatment, as compared to the use of unialgal inocula, besides providing useful pointers for future research needs in this area.