Explanation:
Abstract
Ever increasing population, urbanization and modernization are posing problems of sewage disposal and contamination of surface waters like lakes. Natural water gets contaminated due to weathering of rocks, leaching of soils and mining processing, etc. Various types of problems in lake which cause nutrient enrichment in lake have been reviewed. Land use change and longer growing seasons could increase the use of fertilizers with subsequent leaching to watercourses, rivers and lakes, increasing the risk of eutrophication and loss of biodiversity. Water quality can be assessed by various parameters such as BOD, temperature, electrical conductivity, nitrate, phosphorus, potassium, dissolved oxygen, etc. Heavy metals such as Pb, Cr, Fe, Hg, etc. are of special concern because they produce water or chronic poisoning in aquatic animals. Harmful algal blooms are becoming increasingly common in freshwater ecosystems globally. Pollution by plastic debris is an increasing environmental concern in water bodies, where it affects open-water, shoreline and benthic environments. Surface water densities of plastics are as high as those reported for areas of litter accumulation within oceanic gyres. Different methods have been used to analyse the water quality of lake such as Hyperion, water quality index and hazard quotient. It is recommended that pollution prevention and water re-use should be adopted in combination with the recycling of nutrients in controlled urban agriculture.
Introduction
Lakes are inland bodies of water that lack any direct exchange with an ocean. Lake ecosystems are made up of physical, chemical and biological properties contained within these water bodies. Lakes may contain fresh or salt water (in arid regions). They may be shallow or deep, permanent or temporary. Lakes of all types share many ecological and biogeochemical processes and their study falls within the discipline of ‘limnology’. Lakes are superb habitats for the study of ecosystem dynamics: interactions among biological, chemical and physical processes are frequently either quantitatively or qualitatively distinct from those on land or in air. Because the boundaries between water and land and water and air are distinct, there is tight coupling among many ecosystem components. The isolated lakes are saline due to evaporation or groundwater inputs. Depending on its origin, a lake may occur anywhere within a river basin. A headwater lake has no single river input but is maintained by inflow from many small tributary streams, by direct surface rainfall and by groundwater inflow. Such lakes almost invariably have a single river output. Further downstream in river basins, lakes have a major input and one major output, with the water balance from input to output varying as a function of additional sources of water. Although lakes contain 50.01 % of all the water on the Earth’s surface, they hold 49.8 % of the liquid surface freshwater. Many organisms depend on freshwater for survival and humans frequently depend on lakes for a great many ‘goods and services’ such as drinking water, waste removal, fisheries, agricultural irrigation, industrial activity and recreation. For these reasons lakes are important ecosystems (Fig. 1).
Fig. 1
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Zonation of a lake
Full size image
Lake zonation
Lakes normally consist of four distinct zones which provide a variety of ecological niches for different species of plant and animal life. These zones are:
Littoral zone
The shallow, nutrient-rich waters near the shore, contain rooted aquatic plants and an abundance of other forms of aquatic life.
Limnetic zone
The open-water surface layer receives sufficient sunlight for photosynthesis and contains varying amounts of floating phytoplankton, plant-eating zooplankton and fish, depending on the availability of plant nutrients.
Profundal zone
This zone of deep water not penetrated by sunlight is inhabited mostly by fish, such as bass and trout that are adapted to its cooler, darker water and lower levels of dissolved oxygen.
Benthic zone
This zone is deepest and located at the bottom of the lake is inhabited primarily by large numbers of bacteria, fungi, bloodworms and other decomposers which live on dead plant debris, animal remains and animal wastes that float down from above.
Origin of lakes
Lakes are ephemeral. They originate as a product of geological processes and terminate as a result of the loss of the ponding mechanism, by evaporation caused by changes in the hydrological balance, or by in filling caused by sedimentation. The mechanisms of origin are numerous and are reviewed by (Chapman 1996), who differentiated 11 major lake types, sub-divided into 76 sub-types.
