Living Organisms As Indicators of Pollutants In Fresh Water Ecosystems

Hubers, Hendriekje                 Chicago High School for 
                                   Agricultural Sciences 
                                   (312) 881-5000
                      

Objectives:

1.  Use Hydra as a biological indicator of water pollution.
2.  Learn about Hydra's natural environment, feeding behavior, 
    reproduction, and reactions to stimuli.


Materials:

2-4 water samples from local ponds, streams, lakes, or rivers
1   glass culture dish (or depression slides)
    Hydra population
    Hydra medium
    Brine shrimp or Daphnea
4-6 droppers or pipettes
    microprojector or microscopes
    heat filter

Strategies:

    A Hydra population can be maintained and reproduced in the 
classroom.  If Brine Shrimp are fed to the Hydra, make sure the salt 
water is rinsed off, otherwise you will kill your Hydra.  Daphnea can 
also be used as food for your Hydra. 

1.  With a dropper remove one Hydra (with some water) and place on a 
    culture dish or depression slide.  If you use a culture dish, you 
    can prepare more than one Hydra for later observation.  Place the 
    culture dish on the stage of the microprojector.  Before turning 
    on the light source, place a heat filter above the culture dish (a 
    petri dish with water makes a good heat filter). 
2.  Observe and record the Hydra's structure and movements.  You may 
    also want to discuss Hydra's reproductive behavior and how it 
    changes depending on the environmental conditions. 
3.  With a dropper place one Daphnea or Brine Shrimp (make sure you 
    have rinsed the salt water off) in the dish with the Hydra.  
    Observe and record your observations on the Hydra's feeding 
    behavior.     
4.  Look at the pond and lake water samples.  Discuss with students 
    which sample they think is the most contaminated and why, and what 
    effects they think each water sample will have on the Hydra when 
    added to the Hydra's environment.  You can use as many water 
    samples as you want, just make sure that only one type of water is 
    added to each Hydra.
5.  Add one drop of water from source A to one Hydra sample.  Observe 
    and record your observations.  Set this sample aside, you will 
    come back to observe it in about 10 minutes.
6.  Repeat step 5 using water from source B.  Repeat for as many water 
    samples as you want to study.
7.  After 10 minutes for each sample, observe again and record if 
    there are any changes.
8.  Write your conclusion on your observations.

Evaluation:

1.  Research other types of biological indicators and write a strategy 
    for how you could use this organism to determine the presence of
    contaminants in any kind of ecosystem.

Note: Another demonstration which can be done in class is using Elodea
as an indicator.  Use the same type of set-up you would use for 
demonstrating photosynthesis.