International Journal of Lakes and Rivers. ISSN 0973-4570 Volume 7, Number 1 (2014), pp. 11-24 © Research India Publications http://www.ripublication.com Nutrient Cycles in Lakes D. Suresh Kumar and Dr. V. Sekaran PhD Scholar, Department of Civil Engineering, Karpagam University, Coimbatore, Tamilnadu (E-mail: surea63@yahoo. co. in). Guided, Dean of Civil Engineering, Paavai Engineering College, Pachal, Namakkal Dist. Tamilnadu (E-mail: vsek01@yahoo. com) ABSTRACT All changes in the biosphere can be described by cycles. Cycles can be drawn up for any element, but in biology, that of oxygen, carbon, nitrogen, phosphor, sulphur, as well as water are of interest. The patterns of cycling nutrients in the biosphere involves not only metabolism by living organisms, but also a series of strictly abiotic chemical reactions. Understanding the cycling of biologically important elements is truly interdisciplinary in nature. All biogeochemical cycles for all ecologically significant elements have both an organic and an inorganic component. Both are extremely important. How efficiently the nutrients move through the organic component back to the inorganic reservoirs determines how much is available to organisms over the short term. The major reservoirs for all metabolically important elements are found either in the atmosphere, lithosphere (mainly rock, soil and other weathered sediments) or hydrosphere. Eutrophication is the term used to express the ageing of a lake. It occurs naturally in the environment and the associated time span can be measured in the geological timeframe. However in the last few centuries' man has rapidly increased his use of nutrients, especially in agricultural fertilizers and detergents, many of which end up in waterways and accelerate the process of Eutrophication. As the population continues to increase, a need for more sustainable agricultural practices invokes more technology and fertilization procedures to increase yield. With these fertilizers come nutrients such as phosphate and nitrogen, which can result in the acceleration of the Eutrophication process. In addition to agricultural processes, wastewater treatment plays a major role as well as phosphate removal from detergents. These sources will be examined as well as controls and management strategies that have been implemented to control the problem of eutrophic lakes. Lakes are valuable natural resources. The lake and its surrounding watershed provide important habitats for numerous aquatic and terrestrial wildlife. In addition, lakes encourage the influx of both people and businesses because of the recreational opportunities they provide. Human activity has the potential to drastically alter the natural processes within a lake.