Name
Environmental Science—Mr. Nelson
Eutrophication Lab
Eutrophication is a process in which bodies of water, such as ponds, lakes, streams, and
rivers become rich in nutrients and initially experience increased plant growth. But as the plants
die and decompose, oxygen is used up and the body of water becomes unable to support
aquatic life. It is a natural process that usually occurs over many years, but can be accelerated by
human activities. When caused by human activities, this process is known as cultural
eutrophication. Cultural eutrophication is occurring in some areas due to runoff of fertilizers,
dumping of sewage, and other sources of water pollution. A common result of cultural
eutrophication is a rapid increase algae growth, known as an algal bloom. The water becomes
covered with mats of green, brown, or red algae. As the algae dies, microorganisms decompose
the remains, depleting oxygen in the water and killing fish and other aquatic organisms
sensitive to low oxygen levels. Some bodies of water are more prone to experience the adverse
effects of cultural eutrophication. In this lab, you will investigate the effects of excess nutrients
on water quality in lakes and rivers and predict which body of water is more likely to be
adversely affected by cultural eutrophication.
OBJECTIVES
Investigate the effects of excess nutrients on water quality in lakes and rivers.
Predict which type of body of water is more adversely affected by cultural eutrophication.
ASK A QUESTION: Research and answer the following two questions.
1. How do excess nutrients (fertilizers) affect water quality in lakes and rivers?
2. Are lakes or rivers more susceptible to adverse effects from excess nutrients?
FORM A HYPOTHESIS
3. Form a hypothesis that answers your question. Explain your reasoning.
TEST THE HYPOTHESIS: Mr. Nelson will give instructions as to how we will
set up one class set.
4. Fill each jar half full with distilled water. Then add the same amount of pond water to each
jar. Label one jar “control” (no fertilizer), one as “excess fertilizer no air,” and one as “excess
fertilizer with air.” Decide on the amount of fertilizer to add to your test jars (5 to 10 times
the recommended amount for a given volume of water is a good starting point). Stir the
contents of each jar thoroughly to dissolve all fertilizer. Set up the aquarium pump and
airstone in the excess fertilizer with air jar. Cover each jar loosely with plastic wrap and
place close to a light source or sunny window.
5. Predict what will happen to the contents of each jar.
6. Observe all jars at least every other day for the next two weeks. Note changes in color,
turbidity (clarity), smell of water. Test pH and dissolved oxygen levels of water in each jar.
Enter your data on the Eutrophication Lab Data Chart.
ANALYZE THE RESULTS
1. Explaining Events What is the purpose of the airstone that was placed in one aquarium?
What does the airstone model?
2. Analyzing Results How does excess fertilizer affect water quality in the aquariums?
3. Explaining Events Where does the algae growing in each aquarium come from?
DRAW CONCLUSIONS
1. Making Predictions Predict what might happen to a lake situated close to a golf course.
2. Evaluating Models How do you think this model compares to real-life processes that occur
in lakes and streams that receive nutrient-rich runoff or pollution?
EXTENSION
1. Research and Communication Fertilizers are just one potential cause of cultural
eutrophication. Phosphates in laundry and dishwashing detergents are another. Research
why phosphates could cause cultural eutrophication and what, if anything, is being done to
limit their effects. Write a brief newspaper style article describing your findings.