Testing the
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4:
Biomonitoring
4: Biomonitoring
Introduction | Invitation | Exploration | Explanation | Taking Action | Conclusion
You have tested water for various chemical and physical properties. In this lesson, you will take a field trip to a local stream, river or lake. At this location you can measure flow rate, assess the general appearance of water quality, and collect invertebrate animals to assess the overall water quality.
Objectives
- research the use of macroinvertebrates as water quality indicators (biomonitoring).
- capture and identify macroinvertebrates to assess water quality.
Materials
For this activity, you will need:
- web-links provided
- fine mesh hand nets; trays, jars, or buckets for holding the organisms
- kick nets, drop nets, and seines to be constructed from simple materials (wood, thumbtacks, screen netting etc.)
- small hand held lenses
- two small aquaria or tubs for holding organisms during identification
Put on your old shoes, or even better, slip into a pair of rubber boots or waders, we're going into the stream! It's very fun to tromp around in a creek or shallow stream, and an interesting fact about water quality demands that we do just that. The types of small invertebrate animals that live in a stream will give us a good overall indication of the water quality in that stream. Most of these invertebrates are insect larvae and worms that live under rocks and among leaf litter on the bottom of the stream.
The basic idea is simple. You'll simply need to spread out a fine net across flowing water with the bottom of the net clinging to the bottom of the stream. As another person gently stirs up the rocks ahead of the net, the water flow will take the little animals right into the net. It's fun to identify these little creatures, and very useful for evaluating water quality.
It is best to conduct these type of streams studies when the weather is warm. In cool to cold water conditions, all participants must stay dry and warm to avoid hypothermia!
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Exploration
Before we get equipped for biomonitoring, you will need to do some research. Check out this site on biomonitoring, and print out the taxanomic key for identifying macro-invertebrates. Note the indicator organisms for good, moderate, and poor water quality. Check out these sites for more on biomonitoring:
- Brief explanation of biomonitoring and habitat assessment
- The Rio Grande Global Science Project
- Another source for a taxanomic key with identification diagrams for invertebrates.
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Taking
Action
Part I: Gathering, Making and Using Nets for Biomonitoring
Several tools can be used to collect the organisms living in a stream. The design and use of several net types are described below. These could either be purchased, or constructed from available materials.
1. The kicknet is a large "D" shaped net frame, attached to a long handle. It looks like a shovel. The kicknet allows an individual to hold the net along the bottom of a stream while at the same time kicking and disturbing the rocks in front of the net. The stream flow will wash aquatic organisms into the net, leaving heavier rocks behind. One student with a net is often teamed with another student with a pan for collecting and holding the organisms. You could purchase nets, or make them by adapting fishing nets with a fine mesh lining. Nylon screening or stocking (panty-hose) material works well. The idea is to catch small flowing animals, and many varieties of hand-held nets will work. With the following simple items, you can make your own kick net (your inventiveness and ingenuity will make this a fun process) :
- strong wire coat hanger
- panty hose
- needle & thread
- light handle of some sort
- cord
Straighten the curved top of the hanger and use the cord to lash in to the end of you handle. Spread the reinforced top part of the stocking around the coat-hanger and set it in place so you have a stocking-net secure around the frame. Tie the two legs together so it doesn't look too silly! This is a fragile, but functional device for netting stream invertebrates!
2. A small seine can be operated by three or four students in a shallow, fast-moving part of the stream. Two students hold each side of a stretched out net, supported by two wood poles on each side. This net or seine is held perpendicular to the stream bottom, and spread wide so the water flows into it. It is important that the bottom of the net stays on the bottom of the stream bed. Two other students standing three to five meters ahead of the net should use their feet to disturb the material (rocks, leaves, sand, etc) at the bottom of the stream. As this disturbed water flows into the net, you should catch invertebrates. After the silty water runs through the seine, the two holders gently turn the seine up parallel to the ground. Take the seine to the stream bank to collect organisms from the net.
An invertebrate seine can be constructed from
- black nylon screen
- two wooden poles
- thumbtacks or staples & staplegun.
You can vary the dimensions a bit. A good size for an invertebrate seine is
- two wooden poles about 1.5 meter long, moderate in thickness (2 x 4 cm)
- black nylon screen (mesh size similar to window screen) 1 meter x 1.25 m
Lay the screen
netting out flat, and line up a pole along each of the two
edges that are about one meter tall. Make sure the
bottom of the net is even with the bottom of the poles. You
should have some extra pole to hold above the net when
you're done. Wrap the screen netting one turn around
each pole, then secure the netting to the poles at each side
with flat thumbtacks and staples from a staple gun.
You've just made a "seine" or invertebrate screen
net!
3. The "drop net" is a third and final type of net device works more like "fishing" than "netting". This is a square net that you bait and place on the bottom of slow moving sections of your stream. You leave the net on the bottom, secured by a few rocks atop its frame, then return a day or two later to see what types of animals are present. These drop nets can be purchased, or easily made in your lab.
- Make a square frame from four strong but light strips of wood.
- Attach screen netting to the frame
- Bait with edible material that you can smear & lay along the net (liver and leaf litter)
- Attach a cord with a large floating device to help you find and retrieve the drop net.
Part II: Collection & Identification of Indicator Organisms
Your teacher may divide you into different netting groups. Experienced biomonitors are able to identify the organisms in the field, and return them unharmed to the stream. Since you are new to this, you will probably need to take the invertebrates to the lab for identification. Use the on-line taxanomic keys to help you identify the organisms you collect.
You should set up at least two aquaria containing stream water and perhaps an air pump. This will allow you to have a holding area for organisms that have been, and still need to be identified. Once all the organisms have been identified, they should all be returned to the stream.
While you are at the stream, one group could determine flow rate of the stream. To do this, measure a linear distance along a strait path of water flow (10 to 30 meters is fine). Flow rate, or speed is calculated as distance per unit time, so all you have to do to measure flow rate is time a floating object (an orange or apple or small ball) as it travels the measured distance. Repeat the procedure five times and average the results.
While at the stream,
a visual assessment of water quality, cleanliness, and odor
should be made. One group might want to walk the banks and
determine if a litter-clean-up project is needed. Changes in
flow rate, clarity, depth and width of the stream over a
defined area all add to our knowledge of the
stream.
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Explanation
Present the numbers
of each type of invertebrate collected in a bar graph. You
could record numbers of individuals on the vertical "y" axis
and arrange all the different types of organisms collected
along the horizontal or "x" axis. For an example, look at
the kicknet
data recorded
by other students. Use this data to evaluate the overall
quality of the water in your stream. Post a summary of your
data on the Eco-Connections Project Forum.
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Conclusion
What is the overall condition of your stream, and the stream of your collaborating partners across the globe? How are the stream assessments from the Russia and U. S. sites similar and different? Discuss aspects of this stream study that might be continued in and on-going basis. Is there a need for such research? If there is, who would be willing to "adopt" the stream and continue the monitoring work?
Write a final reflection in which you think about and describe what you have learned from this water-monitoring project.