aquatic ecosystem lab

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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.

   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.

Key Question
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.

Experimental Design
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
      being tested.

   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
      observation day.

Discussion Questions
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
      different? Why?

   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?

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