5.4 Eutrophication

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

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/ wastefertilizersTopsoil erosion

What are the effects? DO levels dropFood chain collapseBiodiversity decreasesContaminated drinking water

Case Study: Lake ErieComplete 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.

Video “ Lake Erie is Dead”

Aerial view of Lake 227 circa 1975Aerial view of Lake 227 circa 1975

Aerial view of Lake 227 in 1994. 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

Experimental Lake 227Previous 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.

Lake 226

Divider Curtain

Possible SolutionsReduce 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 wasteTreat polluted areas by…

Removing algae Pumping air into waterTreat run off and sewage properly