APES
Chapters 17 & 18: Water & Water Pollution
Name___________________________
Date____________ Score___________
Lab: Eutrophication Lab Activity
Eutrophication is the natural aging process of lakes. This very slow process,
which ultimately transforms aquatic environments into terrestrial habitats,
begins with the addition of nutrients into the system. These nutrients in turn
stimulate the growth of microscopic free-floating algae known as
phytoplankton. The term eutrophication is also used to describe the human
induced process where by human activity such as agriculture, use of fertilizers, and changes
in land surrounding aquatic environments accelerates the growth of phytoplankton.
Eutrophic is Greek for “good food”.
A more accurate term for this process is cultural eutrophication. Cultural eutrophication is the
accelerated enrichment of surface waters due human activities. Like the natural process of
eutrophication, this process results in the excessive growth of phytoplankton (algal bloom)
caused by the over-enrichment of nutrients.
Nutrients enter aquatic environments as dissolved solutes and compounds bound
to organic and inorganic particles. Rivers and streams are mainly responsible for the
loading of nutrients to aquatic environments. Loading is the amount of nutrients
delivered to aquatic environments by way of rivers, streams, or groundwater. Nutrients
enter rivers and streams from both point and non-point sources. Point sources are those
from which nutrients are directly being released into the environment. A sewage
discharge pipe draining into a river is an example of a point source of nutrients. On the
other hand, non-point sources enter the environment from no specific point. Runoff
from an agricultural field that washes into a nearby stream after it rains is an example of a
non point source.
1. What is the difference between cultural eutrophication and eutrophication?
2. What are the physical factors that influence cultural eutrophication?
3. What are the biological factors that influence cultural eutrophication?
4. What are the effects on an aquatic ecosystem from cultural eutrophication?
5. Nitrogen, phosphorous and potassium are the major nutrients found in commercial fertilizers. What
role do each of these nutrients have on plant growth and development?
a. Nitrogen:
b. Phosphorous
c. Potassium (Potash)
Begin Cultural Eutrophication Lab
Problem: How much algae(cells) is produced when nutrients such as fertilizers in a form of nitratephosphate, pure phosphate and pure nitrogen fertilizers are introduced into a lake, stream, or pond?
Note: You will be assigned a fertilizer to test over the next 5 days.
Materials: Fertilizer with N-P-K ratio of_____________
Phosphate Fertilizer with N-P-K ratio of 0-45-0
Nitrogen Fertilizer with N-P-K ratio of 30-0-0
Pond Water
3 jars
Graduated cylinders
Microscope Slides and coverslips
Procedures: Follow the directions at your lab table.
Write a hypothesis for your fertilizer’s effect on the pond water sample:
If____________________________________________________________________________________________
Then_________________________________________________________________________________________.
Analysis Data Table 1: Qualitative Observations
Day
Control
Low N or P or NP
Data Table 2: Quantitative Observations
Pollutant
Number of Cells per Drop Undiluted
Tested
Field 1
Field 2
Field 3
Field 4
N or P or NP
Control
Low
High
Assessment:
High N or P or NP
Total number of Algal Cells
(Total # of Cells x 600)
1. Was your hypothesis supported or not supported? Why or why not?
2. How did the addition of the fertilizers affect your pond water samples?
a. Nitrate?
b. Phosphate?
c. Nitrate-phosphate?
3. Did the combination of nitrate and phosphate yield a greater effect than the nitrates and
phosphates alone?
4. How did an increase in the concentration of pollutants affect the amount of algae in the sample?
5. Below is a graph showing the relationship between the amount of rainfall in a community and the
number of algal cells per milliliter of water found in their local water sources. Explain why you believe
the graph is displaying the relationship that it is.
# of Algal Cells/ml Water
Amount of rainfall
6. What types of experimental error occurred in this lab?
7. State any improvements you would make to this lab.
8. How would you reverse the effects of eutrophication in a pond, lake, etc.?
6. What are the EPA criteria levels for Region VIII (northern Great Lakes region) for :
a. total phosphorous: 8 ug/L
b. total nitrogen: .24 mg/L
c. chlorophyll a: 2.43 ug/L (density of phytoplankton)
d. Secchi depth: 4.93 m
(importance of this measurement: measurement of water clarity