Download Eutrophication

Read Phosphorus Cycle (p. 79)
Nutrient Limitation:
Primary Productivity – the rate at which organic matter is created by
producers
Is controlled by:
Limiting nutrient – single nutrient that either is scarce or cycles very slowly,
limiting the growth of organisms in an ecosystem
Eutrophication:
Process whereby bodies of water, such as lakes, estuaries, or slow-moving
streams receive excess nutrients that stimulate excessive plant growth (algae,
weeds)
This enhanced plant growth, often called an algal bloom, reduces dissolved
oxygen in the water when dead plant material decomposes and can cause
other organisms to die.
HOW?
Decomposers need oxygen and a food source to live.
More food (dead organic material from algal bloom or seaweeds)= More
oxygen utilized
More oxygen utilized by decomposers means less oxygen for other
organisms living in the aquatic system
Eventually other organisms (fish, crayfish, insects, other vegetation) die off
due to a lack of oxygen
Hypoxia – “Hypoxia occurs … when oxygen concentrations fall below the
level necessary to sustain most animal life. Hypoxia results when oxygen
consumption, primarily through decomposing organic material, exceeds
oxygen production through photosynthesis and replenishment from the
atmosphere.”
- Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, 2004
Figure 1: Hungabee Lake (left), in the Canadian Rockies, is a crystal clear blue lake. In
contrast, Lake Taihu (right) in China is considered a highly eutrophic lake; note its bright
green color.
-http://www.lakescientist.com/learn-about-lakes/waterquality/eutrophication.html