Name ______________________________ Class ___________________ Date __________________
Skills Practice Lab
DATASHEET FOR IN-TEXT LAB
Eutrophication: Too Much of a Good
Thing?
Plants depend on nutrients such as phosphates and nitrates to survive. However,
when people release large amounts of these nutrients into rivers and lakes,
artificial eutrophication can occur. In artificial eutrophication, nutrients cause
algae and plant life to grow rapidly and then die off and decay. When micro
organisms decompose the algae and plant matter, they use up oxygen in the water,
which causes the death of fish and other animals that depend on oxygen for
survival. Eutrophication is commonly caused by phosphates, which are often
found in detergents, and by nitrates, which are found in animal wastes and
fertilizers. In this lab, you will observe artificial eutrophication in an aquatic
ecosystem.
OBJECTIVES
Observe the effects of nitrates and phosphates on an aquatic ecosystem.
Compare the growth of organisms in different levels of nutrients.
Predict possible effects nitrates and phosphates would have on an aquatic
ecosystem in your area.
MATERIALS
• distilled water
• microscope
• eyedropper
• microscope slides with coverslips
• fertilizer, household use
• plastic wrap
• fluorescent lamp
• pond water that contains
• graduated cylinder
• guide to pond life identification
• jars, 1 qt (3)
viableorganisms
• stirring rod
• wax pencil
Procedure
1. Working with your team, use a wax pencil to label one jar “Control,” a second
jar “Fertilizer,” and a third jar “Excess fertilizer.”
2. Put 750 mL of distilled water in each of the three jars. Read the label on the
fertilizer container to determine the recommended dilution of fertilizer for
watering plants. To the “Fertilizer” jar, add the amount of fertilizer
recommended for a quart of water. To the “Excess fertilizer” jar, add 10 times
this amount of fertilizer. Stir the contents of each jar thoroughly to dissolve the
fertilizer.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
20
Aquatic Ecosystems
Name ______________________________ Class ___________________ Date __________________
Eutrophication: Too Much of a Good Thing? continued
3. Obtain a sample of pond water. Stir it gently but thoroughly to ensure that the
organisms in it are evenly distributed. Measure 100 mL of pond water into
each of the three jars.
4. Cover each jar loosely with plastic wrap. Place all three jars about 20 cm from
a fluorescent lamp. (Do not place the jars in direct sunlight, as this may cause
them to heat up too much.)
5. Observe a drop of pond water from your sample, under the microscope. In the
space below, draw at least four different organisms that you see. Determine
whether the organisms are algae (usually green) or consumers (usually able to
move). Describe the total number and type of organisms that you see
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
6. Based on what you have learned about eutrophication, make a prediction about
how the pond organisms will grow in each of the three jars.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
21
Aquatic Ecosystems
Name ______________________________ Class ___________________ Date __________________
Eutrophication: Too Much of a Good Thing? continued
7. Observe the jars when you first set them up and at least once every three days
for the next 3 weeks. Make a data table to record the date, color, odor, and any
other observations you make for each jar.
8. When life-forms begin to be visible in the jars (probably after a week), use an
eye dropper to remove a sample of organisms from each jar and observe the
sample under the microscope. Record your observations.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
9. At the end of your 3-week observation period, again remove a sample from
each jar and observe it under the microscope. Draw at least four of the most
abundant organisms that you see, and describe how the number and type of
organisms have changed.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
Analysis
1. Describing Events After three weeks, which jar shows the most abundant
growth of algae? What may have caused this growth?
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
2. Analyzing Data Did you observe any effects on organisms other than algae in
the jar that had the most abundant algae growth? Explain.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
22
Aquatic Ecosystems
Name ______________________________ Class ___________________ Date __________________
Eutrophication: Too Much of a Good Thing? continued
Conclusions
3. Applying Conclusions Did your observations match your predictions? Explain.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
4. Drawing Conclusions How can artificial eutrophication be prevented in
natural water bodies?
_______________________________________________________________
_______________________________________________________________
Extension
1. Designing Experiments Modify the experiment by using household dishwashing detergent instead of household fertilizer. Are the results different?
_______________________________________________________________
_______________________________________________________________
2. Research and Communications Research the watersheds that are located close
to your area. How might activities such as farming and building affect water
sheds?
_______________________________________________________________
_______________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
23
Aquatic Ecosystems
TEACHER RESOURCE PAGE
Skills Practice Lab
DATASHEET FOR IN-TEXT LAB
Eutrophication: Too Much of a Good
Thing?
Teacher Notes
TIME REQUIRED One 45-minute period for set-up,
plus follow-up observations over a 3-week period
SKILLS ACQUIRED
Predicting
Designing experiments
Experimenting
Collecting data
Interpreting
Organizing and Analyzing Data
RATING
Teacher Prep–2
Student Set-Up–2
Concept Level–3
Clean Up–2
THE SCIENTIFIC METHOD
Form a Hypothesis Students predict how pond organisms will grow in Procedure
step 6.
Analyze Results Analysis question 2 asks student to analyze data to determine
whether organisms other than algae were affected by abundant algae growth.
Draw Conclusions Conclusions question 4 requires students to draw conclusions
about preventing eutrophication.
MATERIALS
You may substitute plastic soda bottles for the empty jars.
Collect a 5 L water sample from a local, natural, open watershed. When
collecting pond water, plankton nets are helpful for concentrating micro
organisms in the sample. Make sure the sample includes some algae and a small
amount of mud. Preview the sample to be sure that all desired organisms are
identifiable.
As an alternative to collecting pond samples, you might leave tap water in a
container for 24 hours to allow any chlorine to dissipate or use a chlorine
neutralizer for aquariums. Add a stock algae culture such as Spirogyra or
Chlorella to the water. The stock culture will not provide the natural diversity that
natural pond water would provide, but it will enable students to observe algae
growth and will model the results of eutrophication.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
52
Aquatic Ecosystems
TEACHER RESOURCE PAGE
Eutrophication: Too Much of a Good Thing? continued
SAFETY CAUTIONS
Encourage students to wear comfortable, seasonal clothing. Old clothes and
waterproof shoes or boots are advisable when working in aquatic habitats.
Students should wear goggles, gloves, and protective clothing while handling
chemicals such as fertilizer and unknown pond organisms. Be sure to review the
safety cautions on the container of household fertilizer. Students should wash their
hands carefully after handling the pond water samples. Clean the work area with
disinfectant after completing the investigation.
DISPOSAL
Pond water samples that have not been contaminated with chemicals could be
returned to the original collection site. However, you do not want to pollute the
aquatic ecosystem with the fertilizer and detergents used in the experimental
portion of this investigation. Small quantities may be safely flushed down the
drain.
TECHNIQUES TO DEMONSTRATE
Depending on your students’ level of experience with microscope techniques, you
may wish to demonstrate how to make a wet mount. Place a drop of pond water in
the well of the slide with the dropper. Pick up a cover slip and place one edge on
the slide. Slowly lower the other edge so that the water spreads out under it. Be
careful not to trap bubbles of air beneath the cover slip.
TIPS AND TRICKS
You may wish to prepare the containers on the appropriate number of days ahead
of time so students can complete this investigation during one class period.
An alternative method for this lab would be to conduct the experiment using
gradually larger concentrations of fertilizer, such as 1X, 2X, 3X, 4X and so on.
This method would better illustrate the cycle of growth that leads to
eutrophication.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
53
Aquatic Ecosystems
TEACHER RESOURCE PAGE
Name ______________________________ Class ___________________ Date __________________
Skills Practice Lab
DATASHEET FOR IN-TEXT LAB
Eutrophication: Too Much of a Good
Thing?
Plants depend on nutrients such as phosphates and nitrates to survive.
However,when people release large amounts of these nutrients into rivers and
lakes, artificial eutrophication can occur. In artificial eutrophication, nutrients
cause algae and plant life to grow rapidly and then die off and decay. When micro
organisms decompose the algae and plant matter, they use up oxygen in the water,
which causes the death of fish and other animals that depend on oxygen for
survival. Eutrophication is commonly caused by phosphates, which are often
found in detergents, and by nitrates, which are found in animal wastes and
fertilizers. In this lab, you will observe artificial eutrophication in an aquatic
ecosystem.
OBJECTIVES
Observe the effects of nitrates and phosphates on an aquatic ecosystem.
Compare the growth of organisms in different levels of nutrients.
Predict possible effects nitrates and phosphates would have on an aquatic
ecosystem in your area.
MATERIALS
• distilled water
• eyedropper
•
•
•
•
•
fertilizer, household use
fluorescent lamp
graduated cylinder
guide to pond life identification
jars, 1 qt (3)
• microscope
• microscope slides with coverslips
• plastic wrap
• pond water that contains viable
organisms
• stirring rod
• wax pencil
Procedure
1. Working with your team, use a wax pencil to label one jar “Control,” a second
jar “Fertilizer,” and a third jar “Excess fertilizer.”
2. Put 750 mL of distilled water in each of the three jars. Read the label on the
fertilizer container to determine the recommended dilution of fertilizer for
watering plants. To the “Fertilizer” jar, add the amount of fertilizer
recommended for a quart of water. To the “Excess fertilizer” jar, add 10 times
this amount of fertilizer. Stir the contents of each jar thoroughly to dissolve the
fertilizer.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
54
Aquatic Ecosystems
TEACHER RESOURCE PAGE
Name ______________________________ Class ___________________ Date __________________
Eutrophication: Too Much of a Good Thing? continued
3. Obtain a sample of pond water. Stir it gently but thoroughly to ensure that the
organisms in it are evenly distributed. Measure 100 mL of pond water into
each of the three jars.
4. Cover each jar loosely with plastic wrap. Place all three jars about 20 cm from
a fluorescent lamp. (Do not place the jars in direct sunlight, as this may cause
them to heat up too much.)
5. Observe a drop of pond water from your sample, under the microscope. In the
space below, draw at least four different organisms that you see. Determine
whether the organisms are algae (usually green) or consumers (usually able to
move). Describe the total number and type of organisms that you see.
Answers may vary.____________________________________________________
____________________________________________________________________
____________________________________________________________________
6. Based on what you have learned about eutrophication, make a predictionabout
how the pond organisms will grow in each of the three jars.
Answers may vary.____________________________________________________
____________________________________________________________________
____________________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
55
Aquatic Ecosystems
TEACHER RESOURCE PAGE
Name ______________________________ Class ___________________ Date __________________
Eutrophication: Too Much of a Good Thing? continued
7. Observe the jars when you first set them up and at least once every three days
for the next 3 weeks. Make a data table to record the date, color, odor, and any
other observations you make for each jar.
8. When life-forms begin to be visible in the jars (probably after a week), use an
eye dropper to remove a sample of organisms from each jar and observe the
sample under the microscope. Record your observations.
Answers may vary.____________________________________________________
____________________________________________________________________
____________________________________________________________________
9. At the end of your 3-week observation period, again remove a sample from
each jar and observe it under the microscope. Draw at least four of the most
abundant organisms that you see, and describe how the number and type of
organisms have changed.
Answers may vary.____________________________________________________
____________________________________________________________________
____________________________________________________________________
Analysis
1. Describing Events After three weeks, which jar shows the most abundant
growth of algae? What may have caused this growth?
Answers may vary. The jar with excess fertilizer should show the most________
growth. The extra fertilizer stimulated additional plant growth.______________
2. Analyzing Data Did you observe any effects on organisms other than algae in
he jar that had the most abundant algae growth? Explain.
Answers may vary. The jar with the most growth should have the fewest_______
number of microorganisms._____________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
56
Aquatic Ecosystems
TEACHER RESOURCE PAGE
Name ______________________________ Class ___________________ Date __________________
Eutrophication: Too Much of a Good Thing? continued
Conclusions
3. Applying Conclusions Did your observations match your predictions? Explain.
Answers may vary.____________________________________________________
____________________________________________________________________
____________________________________________________________________
4. Drawing Conclusions How can artificial eutrophication be prevented in natural
water bodies?
Artificial eutrophication can be prevented by controlling the application_______
of fertilizers in areas where runoff is common___________________________.
Extension
1. Designing Experiments Modify the experiment by using household dishwashing detergent instead of household fertilizer. Are the results different?
Answers may vary. The samples with dishwashing detergent and_____________
excess dish washing detergent should both show no additional growth._________
2. Research and Communications Research the watersheds that are located close
to your area. How might activities such as farming and building affect water
sheds?
Answers may vary.____________________________________________________
____________________________________________________________________
____________________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Environmental science
57
Aquatic Ecosystems