Eutrophication Nitrogen and Phosphorus are often limiting factors in plant growth. Therefore they are used in fertilizers to improve plant growth. However, eutrophication is when there is “ too much of a good thing”. Excess amount of these nutrients can have harmful affects on aquatic (water) ecosystems.

Eutrophication: Too much of a good thing Eutrophication is the addition of excess nutrients to an aquatic system Fertilizers- N and P Detergents- P Organic waste (manure, sewage) Algal bloom: excessive growth of algae when the normally limiting nutrients (N or P) are increased

Dissolved Oxygen Levels Drop because decomposers use O2 Eutrophication Cont. Overgrowth of algae blocks the light - Algae and other plants begin to die and be decomposed. OR Organic waste can be used directly as food by decomposers Dissolved Oxygen Levels Drop because decomposers use O2 Can result in fish kills and decline of other species

Review with your table partner: What is the initial effect on a lake if excess nutrients get into a lake from runoff of fertilizers on farms? An increase in the population of algae– “ an algal bloom” Note that algae are photosynthetic organisms- how do the algae themselves affect the amount of oxygen? Photosynthesis gives off oxygen, so while the algae are living they increase the amount of oxygen in a lake. The end effect of eutrophication (excess nutrients) is low oxygen in a lake. Explain why this occurs. The mass of algae blocks the light and causes an increase in decomposition of dead algae and plants. The decomposers use up the oxygen.

Eutrophication Animation http://www.youtube.com/watch?v=UGqZsSuG7ao

Puget Sound Dead Zones http://www.youtube.com/watch?v=4JTxVxL_yFM

Eutrophication