IB Environmental Systems and Societies

1. Topic 5
Pollution Management
5.4 Eutrophication

2. What is Eutrophication?
Water body receives too much nitrogen and/or phosphorus
Algal blooms occur due to increased nutrient availability
Increased levels of phytoplankton and algae cut off light to submerged plants
Decomposition of plant material and build up of bacterial populations
Oxygen levels in the water body fall significantly and it
becomes anoxic and unable to support life

3. The Symptoms of Eutrophication
• Increased turbidity
• Increased
sedimentation, reducing water
flow, filling in lakes
• Decreased dissolved oxygen
concentration
• Decreased biodiversity of primary
producers. Loss of submerged
macrophytes
• Toxic cyanobacterial blooms
• Decreased biodiversity of
consumers: fish population
dominated by surface-dwellers
such as pike and perch
http://www.youtube.com/watch?v=0JnKkit5ocI

4. The Impacts of Eutrophication
• Economic losses to farmersdueto loss of
fertiliser from soil
• Health effects from drinking nitrate-rich water
(some disputed links to increased rates of
stomach cancer and blue baby syndrome)
• Loss of water bodies as a public amenity and
scarring of the landscape
• Loss of biodiversity

5. Management Strategies
1. Altering human activities:
– Avoid over-use of artificial fertilisers
– Match fertiliser use carefully to the crop
– Reduce use of fertilisers between mid-September and midFebruary when leaching rates are highest (in the Northern
Hemisphere)
– Give preference to leguminous plants – their roots fix
nitrogen and reduce dependence on fertiliser
– Match fertiliser use carefully to the crop
– Do not apply fertiliser or keep animals close to water
bodies
– Do not plough-up grassland (this released nitrogen)
– Use flat terrain for crops to reduce loss through leaching

6. Management Strategies
2. Clean-up:
– Removal of nutrients by precipitation (e.g. aluminium
or iron salts can be added in order to produce
phosphate precipitates which can be easily removed
and disposed of)
– Removal of nutrient-rich sediments (e.g. by dredging)
– Removal of biomass from affected water bodies (e.g.
removal of predatory fish to allow primary consumers
to recover)
– Prevention of point-source pollution which is known
to be responsible for eutrophication (e.g. nutrient
stripping of effluents, or improved treatment of
sewage effluents to remove nutrients)

7. Management Strategies
3. Regulation (and public campaigns):
– Introduction of phosphate-stripping at sewage
works (by biological nutrient removal or
precipitation)
– Switching to phosphate-free detergents
– Using washing machines only for full-loads
– Reduced use of fertilisers on lawns and public
places
– Punishments for not collecting animal poo
– Compost organic waste rather than send it to
landfill

8. Questions
1. Outline the process of eutrophication
2. Evaluate the impacts of eutrophication
3. Describe three different pollution
management strategies with regard to
eutrophication