Determining Water Quality
Chemical indicators of water quality include measures of dissolved oxygen, phosphates, and nitrate levels, as well as the
temperature and pH of the water. Biological indicators are organisms that reflect how polluted a water system is.
Macroinvertebrates are organisms that are visible to the unaided eye and lack in a backbone. A survey of the number
and type of macroinvertebrates found in the waterway can provide a general indication of the presence of water
pollutants and quality of the water. It is important to keep in mind that organisms found in condition of poor water
quality may be found in any type of water, whereas organisms that are representatives of good-quality water are only
found in water of good quality.
Suggested materials
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Rubber boots or hip waders
Safety waist tether
1.2m3 nylon screen or mesh net with a metal rim
Pan
Turkey baster or plastic forceps
Classification key for macroinvertebrates
Hand lens/dissecting microscope
Thermometer
pH paper
water quality test kits
Pre-Lab questions
1. How can water quality affect biodiversity in a water resource?
2. Name seven types of water pollutants and describe the effects each can have on an aquatic ecosystem.
Question
How can you assess water quality using biological and chemical indicators?
Procedures
Working at a local stream, identify biological and chemical indicators of the quality of water.
Part A: Determining the Biological indicators
1. Collect a sample of organisms from the river or stream by placing the nylon screen or mesh net against the
bottom and kicking against the bottom upstream of the net for at least 1 minute. You should overturn and
scrape any floating debris stirred up by the kicking.
 Note: if you are testing a pond or lake where there is no current, use the net with a metal rim to scoop
material from the bottom mud, especially around the base of any weedy areas.
2. Examine the larger bit of wood that are disturbed by your kicking, since some of the organisms you are
attempting to collect may be stuck to the underside of the wood.
3. Wash away any mud and dirt by shaking the screen or net while holding it partly under the surface of the water.
4. Using a turkey baster or forceps, transfer any collected organisms to the pan or paper plate, and group by shape
Jackson , Ann, Ellen Murray , et al, et al. Environmental Science: A Canadian Perspective. 1. Whitby: McGraw-Hill Ryerson, 2013. Print.
5. Once out of the water, use a classification key and lens (or dissecting microscope) to identify as many organisms
as you can. Macroinvertebrates you might see in waterways near you include crustaceans (such as crayfish),
molluscs (such as clams or mussels), gastropods (such as snails), oligochaetes (such as worms), and insects.
6. As you identity an organism in your sample, record it in a table below. Use the chart to assign a number of
points. Collect at least 10 organisms.
Organism
Points
Organism
Points
7. Return the organisms to the water as close as possible to where you collected them
Part B: determining Chemical Indicators
1. Create a table like the one below
Measurement and Observations
Air Temperature
Water Temperature
Appearance of water
Water pH
Dissolved Oxygen
Dissolved Phosphates
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Measure the air and water temperatures, and record in the table
Determine the pH of the water
Follow the instructions on the water quality kits to determine phosphate
Use the probes to collect data on dissolved oxygen (follow video on proper technique)
Wash your hands once you are finished collecting the samples and performing the measurements
Draw or photograph the site. Note any evidence of
 human activates near the waterway
 vegetation
 geography – generally
 weather conditions when collecting
Analyze and Interpret
1. Determine the quality rating based on the points you assigned the organism collected. Use the following guide
to help determine the quality:
 Excellent (>23)
 Good (17 - 22)
 Fair (11 – 16)
 Poor (<11)
2. What water quality did the test kits indicate?
Jackson , Ann, Ellen Murray , et al, et al. Environmental Science: A Canadian Perspective. 1. Whitby: McGraw-Hill Ryerson, 2013. Print.
Conclude and Communicate
1. Why were you asked to return the organism as close to their collection site as possible.
Jackson , Ann, Ellen Murray , et al, et al. Environmental Science: A Canadian Perspective. 1. Whitby: McGraw-Hill Ryerson, 2013. Print.
Jackson , Ann, Ellen Murray , et al, et al. Environmental Science: A Canadian Perspective. 1. Whitby: McGraw-Hill Ryerson, 2013. Print.