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Topic outline

 

  • Time: 12 hours
    Level: Intermediate

 
 

Introduction

  • Introduction Resource
  • Eutrophication describes the biological effects of an increase in the concentration of nutrients. The collective term ‘nutrients’ refers to those elements that are essential for primary production...
 

1 Introduction

  • 1.1 Origin of the term ‘eutrophication’ Resource
  • The levels of nutrients present determine the trophic state of a water body, where trophic means ‘feeding’.
  • 1.2 Resource availability and species diversity
  • A wide range of ecosystems has been studied in terms of their species diversity and the availability of resources. Each produces an individual relationship between these two variables, but a common pattern...
  • 1.3 Natural eutrophication Resource
  • Eutrophication of habitat can occur without human interference. Nutrient enrichment may affect habitats of any initial trophic state, causing distinctive changes to plant and animal communities. The process...
  • 1.4 Human-induced eutrophication Resource
  • While eutrophication does occur independently of human activity, increasingly it is caused, or amplified, by human inputs. Human activities are causing pollution of water bodies and soils to occur to an...
 

2 Effects of eutrophication

  • Introduction Resource
  • A number of biological changes may occur as a result of eutrophication. Some of these are direct (e.g. stimulation of algal growth in water bodies), while others are indirect (e.g. changes in fish community...
  • 2.1 Effects on primary producers in freshwater ecosystems Resource
  • Plant species differ in their ability to compete as nutrient availability increases. Some floating and submerged macrophyte species are restricted to nutrient-poor waters, while others are typical of nutrient-rich...
  • 2.2 Effects on consumers in freshwater ecosystems Resource
  • Increased productivity tends to increase rates of deoxygenation in the surface layer of lakes. Although phytoplankton release oxygen to the water as a byproduct of photosynthesis during the day, water...
  • 2.3 Effects on terrestrial vegetation Resource
  • Why do you think nitrogen is becoming increasingly available to terrestrial ecosystems in many parts of the world)
  • 2.4 Effects on marine systems Resource
  • In the marine environment, nutrient enrichment is suspected when surface phytoplankton blooms are seen to occur more frequently and for longer periods. Some species of phytoplankton release toxic compounds...
 

3 Causes and mechanisms of eutrophication

  • 3.1 Agents of eutrophication Resource
  • Light availability, water availability, temperature and the supply of plant nutrients are the four most important factors determining NPP. Altered availability of nutrients affects the rate of primary...
  • 3.2 Anthropogenic sources of nutrients Resource
  • In addition to the natural sources of nutrients referred to above, nitrogen and phosphorus enter the environment from a number of anthropogenic sources. These are considered below.
  • 3.3 Mechanisms of eutrophication Resource
  • Direct effects of eutrophication occur when growth of organisms (usually the primary producers) is released from nutrient limitation. The resulting increased NPP becomes available for consumers, either...
 

4 Managing eutrophication

  • Introduction Resource
  • The degree to which eutrophication is considered a problem depends on the place and people concerned. A small lake in South-East Asia, heavily fertilized by village sewage, can provide valuable protein...
  • 4.1 Measuring and monitoring eutrophication Resource
  • During the 1990s there was increased demand in the UK for effective methods of monitoring eutrophication. There was also considerable interest in the development of monitoring systems based on biotic indices....
  • 4.2 Reducing eutrophication Resource
  • In Britain, water supply companies have tended to regard eutrophication as a serious problem only when it becomes impossible to treat drinking water supplies in an economic way. Threshold concentrations...
  • 4.3 Reducing the nutrient source Resource
  • Europe is the continent that has suffered most from eutrophication, and increasing efforts are being made to restore European water bodies damaged by nutrient enrichment. If the ultimate goal is to restore...
  • 4.3 Reducing the nutrient source, continued Resource
  • Wetlands can be used in a similar way to buffer strips as a pollution control mechanism. They often present a relatively cost-effective and practical option for treatment, particularly in environmentally...
  • 4.4 Reducing nutrient availability Resource
  • Once nutrients are in an ecosystem, it is usually much harder and more expensive to remove them than tackle the eutrophication at source. The main methods available are:
 

5 Summary

  • 5 Summary Resource
  • Eutrophication is a process in which an ecosystem accumulates mineral nutrients. It can occur naturally, but is usually associated with human activity that releases nutrients into the environment.
 

References and Acknowledgements

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