AP Environmental ScienceChapters 17 and 18

*Eutrophic Lake

1. Process by which a body of water such as pond, lake, or river has a sudden increase in

algae concentration (high net primary productivity).

2. Caused by the infusion of excess nitrogen & phosphorous nutrients from surface water runoff into local ponds, lakes, river, etc. due to human activity (anthropogenic causes).

*Occasionally, certain conditions—such as an increase in nutrients in the water—can spur the algae to reproduce rapidly, causing harmful “blooms” that can be toxic to ecosystems. 

*Prymnesium parvum, a distant cousin of phytoplankton and giant kelp, is typically found in the ocean and interferes with aquatic org ability to respire underwater. Not toxic to humans /terrestrial animals.

*P. parvum has also recently bloomed in freshwater environments, where they’ve had devastating effects, such as fish kills.

P. Parvum Highly Toxic

Nitrogen exists in environment as:

a.Atmosphere (78% N2)

b.Nitrite (NO3)

c.Nitrate (NO4)

d.Ammonia (NH3) or Ammonium (NH4)

e.Lightning

Phosphorous is commonly found from rocks as PO4.

3. Consequences of Cultural Eutrophication a. Increased algal growth on surface water.

b. Incr. algae causes water to become cloudy

(low turbidity) and decreases dissolved oxygen in water.

c. Algae can release toxins &interfere with aquatic species respiration ability.

d. Underwater plants die from low light attenuation, causing bacteria to decompose plants.

e. Bacteria use up available dissolved oxygen.

f. Massive fish kills occur.

*Agricultural fertilizer run-off

*Recreational areas such a golf courses

*Animal Manure

*Fossil fuel

*Industrial Discharge

*Water sewage power plants effluent

*Found naturally occurring in rocks.

*Found in water systems from sewage transferred from Sewage Treatment Plants (STP)

*Each community has standards to process & neutralize body wastes.

*STP dumps effluent (cleaned

waste water) into local rivers,

lakes, and ponds.

*How can eutrophication of aquatic systems be reversed?