ACTIVITY #3: LAB – FACTORS AFFECTING AN AQUATIC ECOSYSTEM
Student will conduct an inquiry into how factors related to human activity can affect an aquatic
ecosystem, and describe the consequences that this factor has for the sustainability of the ecosystem.
Potentially harmful chemical solutions will be used in this lab activity. Eye protection is to be worn at
all times. Students must be reminded that none of the chemicals used are safe for ingestion. Students
should not be eating or drinking while conducting this inquiry. Bags must be placed out of the way,
and any tripping hazards must be removed.
EQUIPMENT AND MATERIALS
Eye protection dropper bottle of liquid laundry
Stirring rods dilute sulfuric acid detergent
250mL beaker Graduated cylinder electronic balance
(1/student) (1/group) weighing papers
Funnel (1/group) Permanent marker table salt
Hand lens (1/group) 6L pond water
liquid plant fertilizer
Students are to test the effect various chemical factors have on algal growth in an aquatic ecosystem.
This lab does require preparation. The teacher must prepare a 200mL sample of pond water for each
student. For example, if there are 30 students in the class, fill three 2L plastic pop bottles with pond
water. Each student will also require a 250mL beaker to carry out the investigation.
Students should be split into groups of five, where one student in each group will test the effects of
fertilizer, acid rain (dilute sulfuric acid), salt pollution (table salt), detergent run off (laundry
detergent). The remaining student in each group will run a control with no added substance.
As the students are in Grade 9 and many teachers start September with the ecology unit, this will
likely be the first wet lab of the students’ high school careers. Ensure that student groups receive
teacher approval for their proposed added substance amount, and that all safety precautions are
being followed. While this activity requires student documentation of procedure, observations and
completion of questions, a formal lab report (with significant scaffolding) may be assigned in its
Students are to design a table and record their observations every other day for three weeks.
Name: ___________________________________ Date: ________________________ Period: ___________________
Factors Affecting an Aquatic Ecosystem
Ponds, lakes and rivers are valuable aquatic ecosystems. Unfortunately, these ecosystems can be
harmed by human activities. Salt on roads, fertilizer on lawns or even some detergents can flow into
nearby waterways. Acid rain, or rain that contains harmful pollutants, can also enter aquatic
ecosystems, affecting plants and animals that rely on these ecosystems. In this investigation, you will
change an abiotic factor in pond water and observe the effect on the ecosystem.
How might the addition of road salt, fertilizer, detergents or acid rain affect the community or
organisms in an aquatic ecosystem?
Using what you have learned about abiotic factors and aquatic ecosystems so far, write a prediction
(If… Then statement) of the expected result of the experiment.
Each group of five students will examine the effects of changing an abiotic factor in a model pond
ecosystem. The community of organisms in the normal pond water (called the “control”), will be
compares with those in which acid, salt, detergent, or nutrient content of the pond water has been
altered (the “treatments”). Each group will share its results with the class.
1. In your notebook, draw a table similar to the table below. Decide how much of the substance
you will add to your model ecosystem. Record your decision in your table.
Show the table to your teacher for approval before you continue.
Treatment Starting Substance Added Substance
Control 200 mL pond water none
Fertilizer 200 mL pond water __________ mL liquid plant fertilizer
Acid rain 200 mL pond water __________ mL dilute sulfuric acid
Salt pollution 200 mL pond water __________ g salt
Detergent 200 mL pond water __________ mL detergent
2. Label one of your 250 mL beakers “control”. Label other beakers with the abiotic factor your
are investigating: fertilizer treatment, acid rain treatment, detergent treatment, salt pollution
3. Stir the pond water with the stirring rod.
4. Using a beaker or a graduated cylinder and funnel, measure and pour 200 mL of pond water
into each of your labelled 250 mL beakers.
5. Use a hand lens to examine each model pond ecosystem. In your notebook, draw and describe
the organisms you see. Estimate the amount of each type.
6. Measure the substance you are testing. Add it to the pond ecosystem labelled with the factor
7. Design a table to record your observations. Observe your ecosystem every other day for at
least three weeks. Record the types of organisms present and estimate their abundance each
Based on your observations, answer the following questions on a separate sheet of lined paper.
a. Which ecosystem demonstrated the greatest algae growth?
b. Which ecosystem demonstrated the least algae growth?
c. How did your results compare with your prediction?
d. Find other students in the class who tested the same factor. Was their result similar or
e. Assuming there was a constant supply of water, which of your ecosystems do you think could
sustain life over long periods of time? Explain your answer.
f. Based on the class experiment, how might fertilizer, acid rain, detergents or road salt affect
the sustainability of an aquatic ecosystem?