Eutrophication

Excessive richness of nutrients in lake or other water bodies, which causes a dense growth of plant life.

1. DAVANGERE UNIVERSITY MICROBIOLOGY SEMINAR ON THE TOPIC PRESENTED BY : PONNANNA M. B M.Sc . Microbiology. EUTROPHICATION

2. CONTENTS INTRODUCTION TYPES OF EUTROPHICATION MECHANISMS OF EUTROPHICATION SOURCES OF EUTROPHICATION EFFECTS OF EUTROPHICATION SOME EXAMPLES OF EUTROPHIC LAKES CONTROL OF EUTROPHICATION SUMMARY CONCLUSION REFERENCES

3. INTRODUCTION Eutrophication , in Greek sense is   eutrophia , meaning ”nourish well”. O r more precisely  hypertrophication , is the enrichment of a water body with nutrients. This process induces growth of plants and algae and due to the biomass load, may result in oxygen depletion of the water body . One example is the "bloom" or great increase of  phytoplankton in a water body as a response to increased levels of nutrients. Eutrophication is generally induced by the discharge of phosphate-containing  detergents ,  fertilizers , or  sewage , into an aquatic system.

4. TYPES OF EUTROPHICATION 1. Natural eutrophication Although eutrophication is commonly caused by human activities, it can also be a natural process, particularly in lakes .   Paleolimnologists  now recognise that climate change, geology, and other external influences are critical in regulating the natural productivity of lakes. Some lakes also demonstrate the reverse process ( meiotrophication ), becoming less nutrient rich with time.  The main difference between natural and anthropogenic eutrophication is that the natural process is very slow, occurring on geological time scales . 2. Cultural eutrophication Cultural Eutrophication is the process that speeds up natural eutrophication because of human activities . Due to some of the reasons like urbanization ,  land runoff is accelerated and more nutrients such as  phosphates  and  nitrate  are supplied to lakes and rivers, and then to coastal estuaries and bays. Extra nutrients are also supplied by treatment plants, fertilizers , farms, as well as untreated sewage in many cities.

5. NATURAL EUTROPHICATION CULTURAL EUTROPHICATION

6. MECHANISMS OF EUTROPHICATION Eutrophication arises from the oversupply of nutrients, which leads to overgrowth of plants and algae. After such organisms die, the bacterial degradation of their biomass consumes the oxygen in the water, thereby creating the state of  hypoxia . T he primary limiting factor for eutrophication is phosphate . Phosphorus is a necessary nutrient for plants to live, and is the limiting factor for plant growth in many freshwater ecosystems. The availability of phosphorus generally promotes excessive plant growth and decay, on the other hand nitrogen in the form of nitrates also play a vital role in the eutrophication process. Phosphates and nitrates adheres tightly to the soil , so it is mainly transported by leaching and erosion. Once translocated to lakes, the extraction of phosphate becomes tough , hence the difficulty of reversing the effects of eutrophication . The sources of these excess phosphates are phosphates in detergents, industrial/domestic run-offs, and fertilizers emerging as the dominant contributors to eutrophication .

7. Sodium triphosphate , once a component of many detergents, was a major contributor to eutrophication Enhanced growth of aquatic vegetation and algal blooms disrupts normal functioning of aquatic ecosystem causing various problems. The water becomes cloudy with a green , red or yellow shade indicating the algal blooms. These blooms block the penetration of sunlight into the water body, apparently the dissolved oxygen level in the water body also decreases. Lack of oxygen kills the aquatic plants and animals. Death of these organisms and life forms increases the level of organic and inorganic matter, which require large amount of oxygen for decomposition. Now the depletion of oxygen level leads to the accumulation of nutrients unable to be decomposed. Slowly the aquatic ecosystem is converted from aerobic to anaerobic condition, i ncreasing the number of anaerobes which apparently gives a pungent odour generally produced by methanogens and sulphur bacteria . Now this water ecosystem can no longer support life also causing hazardous effects to the environment. Eventually the aquatic ecosystem turns into a bog and gradually converts into a terrestial ecosystem.

8. SOURCES OF EUTROPHICATION Point sources Point sources  are directly attributable to one influence. In point sources the nutrient waste travels directly from source to water. Point sources are relatively easy to regulate. Nonpoint sources Nonpoint source pollution is that which comes from diffused sources. Nonpoint sources are difficult to regulate and usually vary spatially and temporally . Point sources Wastewater effluent ( municipal and industrial) Runoff and leachate from waste disposal systems Runoff and infiltration from animal feedlots Runoff from mines, oil fields, unsewered industrial sites Overflows of combined storm and sanitary sewers Runoff from construction sites . Untreated sewage Nonpoint sources Runoff from agriculture/irrigation Runoff from pasture and range Urban runoff from unsewered areas Septic tank leachate Runoff from construction sites >20,000 m² Runoff from abandoned mines Atmospheric deposition over a water surface Other land activities generating contaminants

9. EFFECTS OF EUTROPHICATION . Primary productivity increases and diversity of primary producers varies. Growth of aquatic plants and algae reduces the light penetration and also increases the turbidity . Death of resident organisms takes place. DO level decreases and sedimentation rate increases. Species diversity is altered , inturn overall aquatic ecosystem is effected. Accumulation of organic and inorganic nutrients. Conversion of aerobic environment to anaerobic inturn altering the appearance , odour of the water body. Anaerobes produce toxins and usage of this water causes health problems. Aquatic ecosystem is depleted.

10. SOME EXAMPLES OF EUTROPHIC LAKES. Udaisagar lake, situated around 13kms in the east of Udaipur revealed high phosphate content due to discharge of pollutants from surrounding phosphorite mines, chemical factories , distillery and domestic effluents. This lake shows a green shade of algal bloom witnessing eutrophication .

11.   Dal  is a lake in Srinagar  , which is named the "Jewel in the crown of Kashmir“ . The lake is also an important source for commercial operations in fishing and water plant harvesting . The lake covers an area of 18 square kilometers (6.9  sq  mi) and is part of a natural wetland which covers 21.1 square kilometers. Due to increasing urbanization , industrial discharge and use of chemical fertilizers in and around the area has resulted in the pollution of the lake causing eutrophication.

12. A view of chelur lake situated near Shimoga district, which is densely covered by aquatic weeds and algal blooms. The reason being the lake is surrounded by agricultural fields, the application of fertilizers in there leach into the lake causing hypertrophication .

13. CONTROL OF EUTROPHICATION. Role of nitrogen and phosphorus is overwhelming in the eutrophication process , which needs to be controlled and affective measures need to be taken. Sources of nitrogen and phosphorus need to be checked and prevented from entering the water body. Timely removal of sediments and overgrown aquatic plants from the water bodies. Stimulation of algal food web. Industrial, municipal and domestic outflow need to be treated prior to releasing. Use of fertilizers to be avoided. Physiochemical methods to be adopted for the removal of excessive dissolved nutrients. Nitrogen testing to be done. Chemicals such as alum, lime , sodium aluminate can be used to reduce the level of contamination. However halting of eutrophication process is difficult, but can be temporarily controlled to some extent.

14. SUMMARY Eutrophication is most commonly associated with the cultural pollution of water with excessive nutrients. The effect of this is rapid increase in biomass, causing both positive and negative effects. Positive effects relate to use as source of fish food, improves biodiversity, enhance ecotourism. Negative effects include decrease in aquatic diversity, human health impacts , ecological impacts. Overall the eutrophication process need to be controlled and affective measures to be implemented in order to replenish the water bodies.

15. CONCLUSION Human induced eutrophication has heavily degraded freshwater systems worldwide by reducing water quality and altering the structure and functioning of ecosystem. With the demand of freshwater sources expected to increase substantially, these anthropogenic influences have severe environmental and economic repercussions. The first obvious step towards protection and restoration of lake is to divert or treat excessive phosphorus inputs via nutrient lodging restrictions. Living organisms can be used as monitors of trophic status of lakes. Nitrogen testing to be done to avoid use of nitrogenous compounds. Phytochemical tests can be achieved to remove excessive nutrients. Effluents and runoff water into the lake need to be treated . It takes a very long time to overcome the problem of eutrophication, but can be minimized to a substantial level by incorporating some of the preventive measures.

16. REFERENCES Maier, R. M., Pepper, I. L. and Gerba , C. P. 2009. Environmental Microbiology ,2 nd edn . Academic press, Amsterdam, 598 pp. Atlas, R. M. 1997.Principles of Microbiology,2 nd edn . McGraw Hill education , New Delhi, 1298 pp. Atlas, R. M. and Bartha , R. 2009. Microbial ecology, fundamentals and applications, 4 th edn . Pearson education, New Delhi. 704 pp. Toratora,G.J ., Funke,B.R . and Case,C.L . 2007. Microbiology an introduction, 11 th edn . Pearson education, South Asia. 975 pp.