Topic: STREAM ECOLOGY FOR ELEMENTARY TEACHERS
Source: A seminar presented in Central Illinois Saturday Science Education Seminars for Elementary Teachers
Presenter: Laura Johnson-Hechtel
Department of Biological Sciences
Illinois State University
Normal, IL 61790
Funded by: Scientific Literacy Center
Illinois State Board of Education
1990-1993
Abstract: Concepts presented are of biological and physical sciences focusing on their application to life and work in a contemporary technological society. Students at all levels could benefit from knowledge of the concepts developed in these activities. A field trip is required, and it will be valuable for you to carefully select the site. Most data can be collected from any stream or ditch with a consistent volume of moving water. Purchased equipment that will be needed include dip nets, stopwatch, hand lenses, waders, seines, and materials for constructing plate samplers. A diagram with materials list has been provided on page 6.
STREAMS (Teacher Copy)
INTRODUCTION
Many schools have small streams running through or near the property. These communities are too often overlooked as an educational laboratory for children. Activities provided in this seminar are designed for elementary teachers and their children.
Objectives
Upon completion of this lab, students should be able to:
1. Recognize major groups of aquatic organisms.
2. Compute the flow of a stream.
3. Determine the stream quality based on the organisms found.
4. Make observations and draw conclusions on habitat needs of organisms.
Background
Continuously moving water is the outstanding feature of streams and rivers. The current of a stream refers to how fast the water moves or flows. The stream's current cuts the channel, molds the character of the stream, and influences the life and activities of organisms inhabiting flowing waters.
Streams may begin as outlets of ponds or lakes or they may arise from springs and seepage areas. Water may also enter a stream through runoff, especially after heavy or prolonged rains and rapid snow melt. Because the amount of rain and snow varies depending on the time of year, the rate and volume of stream flow may change from flood conditions to dry channels.
Water in a stream will always flow from a higher point to a lower point. The greater the differences in height, the faster the current. Water moving downstream, especially where the slope is steep, carries with it a load of debris such as rocks, pebbles, mud, leaves, twigs, branches, etc. This debris helps the stream cut the channel wider and deeper and is sooner or later deposited within or along the stream.
At flood time the stream water overflows its bank into the surrounding area called the flood-plain. The debris carried by the stream is dropped on the level lands, over which the water spreads, to form flood-plain deposits. These flood plains are a part of the stream or river channel used at the time of high water, a fact that few people recognize.
The character of a stream is molded by the speed of the current. This speed varies from stream to stream and within the stream itself. It depends upon the size, shape, and steepness of
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INTRODUCTION Continued
the stream channel, the roughness of the bottom, the depth and the rainfall.
A fast stream is often a series of two very different but related habitats--the turbulent riffle and the quiet pool. The waters of the pool are influenced by processes occurring in the rapids above, and the waters of the rapids are influenced by events in the pool. The speed of flow influences the amount of silt deposited and the type of bottom. The current in the riffles is too fast to allow silt to settle, but coarser particles drop out in the smooth or quiet sections of the stream. Differences in currents between riffles and pools may also result in other environmental differences, such as temperature, turbidity, and oxygen content. Organisms may be restricted to certain areas of the stream due to these differences. For example, organisms that live in swiftly moving water may exhibit a characteristic shape, hold-fast organs, or behaviors that allow them to remain in fast water.
While many forms of water pollution exist, one of the most common is that caused by sewage or fertilizer. When these materials are deposited into a stream they provide nutrients for growth of microorganisms. Decomposition of these organisms depletes the dissolved oxygen supply in the water and reduces or eliminates other aquatic organisms that do not readily adjust to low concentrations of oxygen.
Another common type of pollution is that caused by siltation. Silt can clog the gills of aquatic organisms, smother eggs located in the water, and increase turbidity, making food gathering by sight-dependent fish difficult or impossible. Of course, many other substances may have direct or indirect toxic effects on organisms.
The kind and variety of organisms present in a stream often are a more sensitive indication of pollution than chemical and physical measurements. In polluted waters the number of species present (diversity) usually is reduced. However, some organisms do quite well in polluted waters while others do quite poorly. The mathematical expression of this relationship is called a diversity index. Also, because the presence of certain organisms indicates water quality, a "Biotic Index" can be calculated. In this system all large invertebrates are placed in one of three categories:
Class I organisms are those highly sensitive to pollution. These include, in general, caddisflies, mayflies, stoneflies,
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INTRODUCTION Continued
hellgrammites, riffle beetles, water pennys, and most freshwater clams.
Class II organisms are those that do fairly well in both clean and polluted streams and are most abundant where there is a moderate degree of organic input. Such organisms are damselflies, dragonflies, blackflies, horseflies, craneflies, aquatic sowbugs, crayfish, flatworms, gill snails, and fingernail clams.
Class III organisms are pollution tolerant. These include midges, rat-tailed maggots, mosquito larvae, aquatic earthworms, mothflies, leeches, air-breathing snails, and limpets.
The Biotic Index (BI) is computed: BI = 2 x (No. of Groups of Class I organisms) - (No. of Groups of Class II organisms). A biotic index between 10 and 15 is considered to be the boundary between a clean and polluted stream environment.
STREAMS (Student Copy)
LESSON 1 Stream Characteristics
Background Information
Working in groups of 4, collect the following data on streams. Be sure to stay out of the way of other groups when sampling an area of a stream.
Materials Per Group:
1 dip net 4 large jars
8 small jars 2 pans
1 wash bottle 4 forceps
4 spoons 1 thermometer
1 ping-pong ball 1 tape measure
1 yardstick 1 stopwatch
2 plastic bags 1 magnifying glass
2 plate samplers (get out of stream)
Group Property:
waders, seines, alcohol, labels
Procedure
1. Stream flow
Determine the stream flow for areas of the stream characteristic of a pool and a riffle. Stream flow can be determined accurately enough for our purposes by the following method: Locate an area of the stream that is fairly straight and the water flow is fairly calm and even. Measure the width of the stream in three locations: Point A; at the upper end of this section of the stream, Point C; at the lower end of this section, and Point B; about half way between Points A and C. Record your data on the sheet provided. Determine the depth of the water at the center of the stream at these three locations. Record your data. Then determine the speed or velocity of the current by placing a float that is light, yet rides low in the water and measure, in seconds, the time needed to travel from Points A to C. Make several runs. The volume of flow can be determined by the Embody Formula:
R = W x D x a x L
T
where R = volume of flow in cubic feet per second, W = average width of stream in feet, D = average depth in feet, a = a constant (0.9 for a smooth bottom of mud, sand, or bedrock; 0.08 for coarse gravel or cobbles), T = the average time (in seconds) for a float to traverse the distance, and L = the distance traversed (in feet). R can be converted to gallons/second by taking R times 7.48.
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LESSON 1 Continued
2. Temperature
Although water is flowing constantly through a stream, temperatures may fluctuate depending on the location, which may in turn affect what types of organisms may be found there. Record the temperature at the following locations: air, riffle, surface of pool and bottom of pool.
3. Aquatic Organisms
The types of organisms, or biota, of a stream may be sampled in several ways. A Surber dredge is the most commonly used sampler for collecting stream fauna. It consists of an iron frame with a cone of netting that trails downstream. Another frame lies on the stream bottom directly in front of the mouth of the cone. When the stream bottom inside of this frame is stirred organisms are carried into the net. Thus, equal-sized areas can be sampled and compared.
Another means of sampling aquatic organisms is the use of a dip-net. By making a series of sweeps over a given area, several organisms may be collected. This allows for better sampling under plants growing over the edge of the stream where several animals like to live. However, it should be remembered that this is not a good method to use for controlling the size of the area sampled.
A third method of sampling aquatic organisms is by use of a plate sampler (Figure 1). Aquatic organisms normally found under or between rocks or in sediment will colonize the plates. This method of course takes time and works best if plates can be placed in the stream 4 weeks prior to removal. To remove the samplers, quickly pick up the sampler inside a large plastic bag so no organisms can escape with the water. Use sieves and wash bottles to remove mud and debris.
Make several samples of both the pool and riffle areas using the dip nets or Surber dredge. After washing to remove mud, the material can then be dumped into pans for examination and sorting. Record the types of animals found.
STREAMS (Student Copy)
LESSON 1 Continued
Figure 1: Plate Sampler
乔乔<___________ 2 hexnuts
北北北<___________ washer
/ 北北北______________ washer
3" x 3" tempered /圹\ ___________ wing-nut
hardboard /_/圹\_\
separated by 圹
1/8" thick spacers 圹
圹___1/4 inch bolt
圹
STREAMS (Student Copy)
Stream Characteristics
Pool Riffle
Stream width: Point A _________________ ft Point A _______________ ft
(W)
Point B _________________ ft Point B _______________ ft
Point C _________________ ft Point C _______________ ft
Average _________________ ft Average _______________ ft
Stream depth: Point A _________________ ft Point A _______________ ft
(D)
Point B _________________ ft Point B _______________ ft
Point C _________________ ft Point C _______________ ft
Average _________________ ft
Distance from
Points A to C: ________________________ ft ________________________ ft
(L)
Time
traveled: _______________________ sec _______________________ sec
(T)
_______________________ sec _______________________ sec
_______________________ sec _______________________ sec
average _______________________ sec _______________________ sec
Stream flow: Pool Riffle
W (use average above) = __________________ _________________
D (use average above) = __________________ _________________
a = 0.9 0.8
T (use average above) = __________________ _________________
L = __________________ _________________
R = W x D x a x L = __________________ _________________
T
Temperature: air __________________, riffle ____________________
surface of pool ___________________________
bottom of pool ___________________________
STREAMS (Student Copy)
Aquatic organisms
Pool
Name of Number Description
Organism found
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
Riffle
Name of Number Description
Organism found
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
STREAMS (Student Copy)
Plate Samplers
Name of Number Description
Organism found
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
____________________ _____ ____________________________________________
Extensions/Variations
4. Compare the type of organisms you find in the pool and riffle. How are they different? similar? Does stream flow affect this distribution?
5. Compare the animals you find with a dip net from the middle of the stream and along the edge. If they differ, can you explain this distribution?
6. Compare the animals you find with a dip net verses the plate samplers. Explain any differences you see.
7. Based on the types of organisms you found, would you classify this stream as polluted or clean or somewhere in between?
What BI rating did you give it?
(Pictures and descriptions of dragonflies, damselflies,
mayflies, caddis flies, alderfly, midges, limpet,
aquatic sowbugs, and crayfish.)
Figure 2