1. 5.4 Eutrophication

2. What is it?
Eutrophication is the addition of excessive nutrients (animal waste, fertilizer, sewage) to a body of water (runoff) and causes excessive algae growth to occur.
Dense algae growth blocks out light and kills aquatic plants
Decaying plants causes a severe loss of oxygen (no photosynthesis)  Low DO Levels
Bacteria flourish as a result of all the decay and deplete the oxygen supply of water  High BOD levels
Fish and consumers die due to lack of oxygen

3. What causes it? Eutrophication can be a natural process
Accelerated greatly by addition of nitrates and phosphates.
Largely a result of run off of…
detergents,
Sewage/ waste
fertilizers
Topsoil erosion

4. What are the effects? DO levels drop Food chain collapse
Biodiversity decreases
Contaminated drinking water

6. Case Study: Lake Erie Complete the assignment “Lake Erie is Dead!”
The “death” of Lake Erie in 1960’s
Eutrophication caused by dumping a lot of detergents and fertilizers over short period of time.
Some lakes were designated to study the effects of eutrophication.
The following slides are the results of the experiment.

7. Video “ Lake Erie is Dead”

8. Aerial view of Lake 227 circa 1975

9. Aerial view of Lake 227 in Note the bright green color caused by algae stimulated by the experimental addition of phosphorus for the 26th consecutive year. Lake 305 in the background is unfertilized.
Aerial view of Lake 227 in 1994

10. Experimental Lake 227
Previous Slide: Bright green color shows algae growth caused by experimental addition of phosphorus for 26 years.
Lake 305 in the background is unfertilized.
Next Slide: Lake 226 with a divider curtain in August 1973.
The bright green color results from bluegreen algae (Cyanobacteria), which are growing on phosphorus added to the near side of the curtain.

11. Lake 226
Divider Curtain

12. Possible Solutions Reduce nutrients released into water ways
Reduce use/production of phosphate detergents
Restore wetlands to act as buffer zones between farms and surface waters
Reduce amount of livestock = less waste
Treat polluted areas by…
Removing algae
Pumping air into water
Treat run off and sewage properly