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| journal page pdf |
Lake & Stream |  |
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| journal page pdf |
Lake & Stream | |
The Wolf Ridge Lake and Stream Study classes provides many extension possiblilites for the classroom. Tie-ins can be made to a variety of topics including biodiversity, insect life cycles, adaptations, water quality, chemistry, the physics of water, and more. Visit this page periodically as we will add new activities and links suggested by Wolf Ridge visiting school teachers, and eventually our own interactive on-line activities.
Aquatic Ecology Study at your school
You may wish to replicate the Lake Study class activities your students do at Wolf Ridge in a lake, stream, or pond in your home community. This will enable them to make broader comparisons of aquatic animal study based on different times of year, locations, and aquatic habitats.
These step-by step teacher instructions, equipment lists, and worksheets should help make it easier to get your class outside and wading into aquatic habitats. Most of the equipment is easy to make, find, or borrow.
The main goal of this activity is to determine the general health of your local lake or stream. Is it healthy or not? If you do this activity each year, do records show any change? People can often directly sense a problem with water quality. It may smell funny or look purple and gross. We can look for life and notice if something is missing or an unusual species is present. Many times our senses are not accurate enough to test water quality. Chemical tests enable students to measure dissolved oxygen and acids in the water. Finally students will collect a wide range of aquatic animals to identify and observe.
Step 1. Choose a site to visit
Factors to consider when choosing a local aquatic habitat to visit include:
Step 2. Gather Equipment
For a class of 20 Wolf Ridge uses:
Equipment Sources used by Wolf Ridge:
Step 3. Set Ground Rules and Expectations
If students have already visited Wolf Ridge, they will be familiar with the equipment, and will just need a review and your ground rules and expectations.
Step 4. Review Background Information and Equipment Use
A. Physical Properties
1. Temperature
Taking the temperature of the lake is easy. Take temperature readings of the air, the water’s surface, deep water, and perhaps sunny and shady areas of the lake. Be sure to dry the thermometer before doing the air temperature so evaporation doesn’t affect the reading. Hold the thermometer by the dial, not the sensing tip. Let it remain in position for at least one minute to stabilize. Read the numbers quickly and record the results on the data sheet.
Temperature is an important factor for all aquatic life. Since water in lakes and streams never gets below 0&Mac251;C (32° F) it is a safe haven for creatures that can’t handle cold winter weather.
Temperature also determines the rate of chemical and metabolic reactions. Warm water allows more and faster reactions to occur. Therefore, warm lakes usually contain more fish which grow bigger and faster than in cold lakes.
Temperature of stream water is important because it dictates how much dissolved oxygen (DO) the water can hold. Cold water has the ability to hold more oxygen than warm water.
2. Bottom Type
At each site, describe the bottom of the lake. This might be sandy, mucky, rocky, gravelly, etc. There may also be logs, plants, slime, etc. found on the bottom of the lake. These are important observations, because certain creatures are adapted to and can be expected to be found in particular bottom types. If there are a variety of bottom types in you study site, list each one and draw arrows to which animals were found in that type.
B. Chemical Properties
1. Dissolved Oxygen
Some aquatic creatures breath air with lungs just like land dwelling animals. Others use gills to obtain dissolved oxygen present in the water. Even the skin of many aquatic animals allow dissolved oxygen to pass right on through to the bloodstream. Frogs for example manage to hibernate all winter underwater without lungs or gills.
Cold water holds more oxygen in solution than warm water, just as cold soda pop keeps its fizz longer than warm soda pop. Rushing streams and wave tossed lakes have more oxygen dissolved into them due to the mixing action of the air.
Animals have differing requirements for dissolved oxygen. Generally 4 to 5 ppm of dissolved oxygen content is the borderline concentration for most gill breathing creatures over an extended period. For adequate game fish populations the dissolved oxygen content should be in the 8 to 15 ppm range. Dissolved oxygen concentration varies with water depth, temperature, clarity and flow rate. Thus a single water sample is rarely representative of the overall condition of a body of water.
We can easily do a chemical test to reveal the concentration of dissolved oxygen in the water. Show the students the dissolved oxygen (DO) test kit contents and demonstrate some of the techniques involved in taking a DO test. Don’t do a complete demonstration test because the sample needs settling time. Show how to stopper the bottle so there are no air bubbles. Demonstrate how to cut the tops off the foil and plastic chemical packets. Stress stewardship and ask students not to throw the packets on the ground, but to keep all trash with the kit. Stress that they will carry even used chemicals back to the classroom in a container for disposal through the septic system. Demonstrate the final titration step by adding drops to the bottle to obtain the final reading. We express the amount of dissolved oxygen in parts per million (ppm.)
2. pH
Another chemical test the students will do is to search for the concentration of acids in the lake. Some acids come from plants (tannic and humeric acids) and are naturally present in the water. Volcanic smoke is also a source of natural acid (sulfuric acid). Some acids are not natural, caused by human activities, and enter streams via rainfall, run-off , or direct discharge from factories or mines. Aquatic life is very sensitive to chemicals in general and most creatures have a very narrow tolerance range for acid.
Acids are substances which react with and tend to dissolve substances.. Acids come in various strengths. The stronger the acid the more rapidly it dissolves. For example, battery acid (sulfuric acid) will make holes in the pants of car mechanics, while a weak acid, like vinegar, does not affect clothes at all. Our bodies can detect the strength of acids by feel and taste. The stronger the acid, the more sour the taste, like citric acid in lemons. Using ourselves as an acid tester, however, is sometimes dangerous, and not very accurate. We therefore use various types of acid test kits. They usually employ an acid sensitive dye that changes color depending on the strength of the acid. The scale used to compare the strengths of acids is call the pH scale. pH stands for the negative logarithm (p) of the hydrogen ion concentration [H+].
<.......... ACID BASE..........>
0 7 14
The scale ranges from 0 to 14, with 7 in the middle at neutral. A neutral substance has no acid at all, such as pure, fresh, distilled water. As the numbers go from 7 down to 0, the acid gets stronger by a factor of 10 for each number in the scale. This means that an acid with a pH of 6 is ten times stronger than pure water (show the dot charts.) An acid with a pH of 5 is on HUNDRED times stronger, 4 is one THOUSAND times stronger, etc. Finally, an acid with a pH of 0 is ten MILLION times stronger than pure water. The other side of the scale measures bases, often called alkalines, which are the opposite of acids. Like acids, they react with other substances, and cause burns if they are strong enough. You can detect a strong base by the feel of it; it may feel slippery, because it is dissolving your skin. The reactions are caused by an excess of OH-rather than H+. If acids and bases are mixed, they neutralize each other, or cancel each other out. Like the acidic side of the scale, the strength of bases is increased ten times for each number greater than 7.
A relatively neutral pH is important for the survival of aquatic plants and animals. When an environment becomes too acid or alkaline then destruction of tissues and disruption of chemical processes becomes a problem.
Some examples of familiar acid/base reactions:
1. Using baking soda and vinegar to make a cake rise. The acid and base react to neutralize each other, eliminate the taste of the vinegar and creating carbon dioxide gas bubbles which cause the cake to rise.
2. The Rolaids commercial which says that it “neutralizes excess stomach acid.” If our stomachs become too acidic, they can cause pain. Rolaids are basic and raise the pH of our stomachs from a painful pH 1.0 back to a more normal pH of 1.5 or 2.0.
C. Biological Properties
1. Capture and Identification
Students will look for and collect aquatic creatures, mostly insects. They may deposit them for closer examination into a white tray half-filled with water. Many insects spend the early part of their lives underwater and grow wings and take to the air only as adults. Insects in all stages of their development are in Wolf Lake.
Simple metamorphosis: (Grasshopper, dragonfly, etc.)
Egg......> ....... Nymph......> .......Adult
Complete metamorphosis: (butterfly, caddisfly, etc.)
Egg .......>.......Larva.......>.......Pupa......> ......Adult
Do not scoop up rocks in the net, since they will put holes in the net. Use the schlurpers to either suck up or rinse off creatures adhering to rocks or bits of wood.
Micro animals and plants are the bottom of the food chain and the basis for all life in a lake or stream. Gently swish the plankton net in the clear, undisturbed water for several minutes. With the help of a partner, drain the contents of the net into a clear jar. Hold the jar up to the sky and carefully examine the contents for movement. Students should be impressed with the quantity of micro-life they observe. Bring the sample jar back to the classroom and examine several drops using a microsope or stereoscope.
Students should identify the other (macro) animals they have found. The ID sheet and Pond Life field guide are very helpful. Keep the critters in your tray within 5&Mac251;C. (10&Mac251;F) of the stream water temperature. At the end of the outdoor session, return all creatures to the lake.
2. Biotic Index
A healthy lake ecosystem (any ecosystem) has a great diversity of species that interrelate with each other. The presence or absence of living creatures is one of the best tests in determining the health of an environment. Many animals are very sensitive to chemical pollution, soil erosion, temperature fluctuations, non-native species, etc. By using a simple formula which considers the pollution tolerance of different species, we can determine water quality. Each species has a group number describing its ability to withstand pollution. Group numbers are found on the "Aquatic Animal ID" sheet. On the data sheet, list the creatures and their group number. Using the following formula, calculate the Biotic Index of Lake Study.
Biotic Index = 2( ___ group I species) + ( ___ group II species).
If the Biotic Index is: 0-2........ The stream is heavily polluted.
4-6........ The stream is moderately polluted.
8-10...... The stream is clean.
Step 4. Go Out and Explore!
Step 5. Organize Data, Draw Inferences, Make Hypotheses . . .
After examining your own lake or stream, see if students can draw some comparisons to Wolf Lake or Sawmill Creek. What was similar? What was different? Can students suggest a hypothesis for the differences or similarities? How might they go about testing that hypothesis?
If possible, keep a journal or other record of the observations students made, including the date. Record data in the same categories in different seasons, years, and bodies of water. Students can graph results over time and use them to make inferences.
In the future, we plan to post Wolf Ridge's stream and lake study data on-line, and may develop a database where you will be able to enter your school's aquatic study data as well. Potentially, students will be able to compare data from around the region over a long period of time.
References:
1. The Life of Rivers and Streams, Robert Usinger, 1967
2. Pond Life, Golden Guide 1967
3. Project Aquatic Wild, 1987
4. Fresh-water Invertebrates of the U.S. 2nd Edition, Robert Pennak 1978, ISBN 0-471-04249-8
5. Fieldbook of Freshwater Life, Elsie Klots, Putnam's and Sons, New York 1966.
6. A Guide to the Study of Freshwater Biology, James G. and Paul R. Needham, ISBN 0-8162-6310-8
7. Ontario Ministry of the Environment, 435 James St. So, Thunder Bay, Ont. P7C SG6
8. Project Stewardship Minnesota, Office of EE, St. Paul, MN 1990. (Biotic Index)
Class Description:
Lake and Stream Study are aquatic ecology classes. Students will examine the physical, chemical and biological properties of Wolf Lake or Sawmill Creek. Wearing boots which are provided, and working in small groups, the students will test temperature, pH and dissolved oxygen. They will use nets to collect and examine aquatic animal life, and will evaluate the health of the lake or stream based on their findings.
Total time: 3 hours (two hours outdoors)
Audience: 6-20 students, 4th grade through adult
Activity level: moderate
Travel: 1 1/2 mile
Total uphill travel: 250 feet
Outcomes
Upon completion of the Lake or Stream Study class students will be able to:
- Understand and measure the temperature, pH, and dissolved oxygen of an aquatic system.
- Examine and report upon the diversity of aquatic creatures captured.
- Recommend actions to preserve healthy lake environments.
Minnesota Graduation Standards
The Lake or Stream Study class will provide students with guided practice, in an authentic setting, to support the following Graduations Standards. We have chosen one to three “major focus” standards per grade level. Due to the holistic nature of environmental education, several other standards, not listed here, are addressed as well.
Profile of Learning Element 6: Understanding and applying scientific concepts in natural and human-made environments.
Biology Standard 6.G8.1 Understands the interactions and interdependence of components of living systems. (Declaratives): Understands components of natural systems, their structure, how they function, and their relationships within a system. Understands implications of interactions between human and living systems. (Procedurals): Given a problem situation involving a complex system, describe a potential problem caused by a breakdown within the system, and for each problem predict effects at both sub-system and system levels. Develop models, explanations, designs, or rules for behavior which illustrate each of the problems and types of change predicted. Demonstrate basic safety procedures and skills when using tools and equipment. (Specifications): Students must be given opportunities to work in authentic settings. One aspect of the problem situation should address environmental concerns.
Ecology Standard 6.G5.1 Understands the components and relationships of living and non-living systems. (Procedurals): Within simulated or real-world situations, models or systems: identify, describe and classify components on the basis of their properties and their energy relationships, describe interactions among components, describe interactions between two of the systems, demonstrate or explain how a change in one of the components would affect the system, use data to predict change, select and use tools and materials appropriately. Demonstrate examples of how personal behaviors and use of materials have a positive impact on the environment. (Specification): Assessments should be related to students’ environment.
Wolf Ridge Curriculum Concepts