Time Required: 45 minutes

Transcription

1 Benthic Macroinvertebrate Study Concept/Topic to Teach: The presence or absence of benthic macroinvertebrates can be used to indicate water quality. Standards: Discipline: Science and Technology Strand: Life Science (Biology) Topic: Living Things and Their Environment 13, 14, and 15. Changes in Ecosystems over Time 17 Grade Level: 5-6 Time Required: 45 minutes General Goal: Students will examine benthic macroinvertebrates to see how they can be an indicator of water quality and habitat health. Sites for collection may be chosen that show how habitat condition can vary depending on water depth and velocity, presence of shade, riffles, etc. By using macroinvertebrate identification/record sheets students will be exposed to the concept that some creatures can only live in relatively clean or completely unpolluted water. Specific Objectives: Students will examine mud/water samples and find a selection of the organisms that are present. Using identification/record sheets the students will identify some of the organisms and assign a water quality rating to each of the specimens. Using the above information, the students will make a tentative evaluation of the health of the body of water from which the mud/water sample was taken, at least for that specific site. Vocabulary: benthic, larva, macroinvertebrate, nymph, pollution tolerant, pollution intolerant, riffles. Required Materials: Materials for Collecting: 1-2 buckets A kitchen strainer if sampling from a pond, or a sturdy net if from a river A container for scooping water Materials for Classroom Observations: Mud, leaves and water collected from your pond or stream White ice cube trays or egg cartons, 1-2 per group Magnifiers, one per child Macroinvertebrate Key, one for every 1-2 children Data Collection Sheet, one per group Plastic containers (food storage containers work well), several per group Plastic spoons (white), one per child Anticipatory Set: Ask the students how animals living in a body of water might be used to determine the water quality of the pond or stream. 21 Quality & sheds

2 Benthic Macroinvertebrate Study continued. Step-by Step Procedure: Collect samples from the habitat to be tested, either using a net in a stream or a kitchen strainer in a pond (this may be done by the lesson presenter before the class). In a pond, many organisms may be found among the vegetation, fallen leaves and/or the mucky bottom, whereas in a stream the organisms attach themselves to the rocks in riffles and can be removed with gentle rubbing. Be sure to return organisms to their original location after the lesson. Introduce the terms macroinvertebrate and benthic (see glossary). Explain that macroinvertebrates can be an indicator of water quality because the different species have varying pollution tolerance levels. Some macroinvertebrates are sensitive to pollution and therefore won t be found in a polluted water body. Macroinvertebrates that are pollution tolerant are the ONLY species found in a polluted water body. It is important for students to realize that pollution tolerant species are found in ALL water qualities, but sensitive species are only found in higher water quality environments. Explain briefly to the students what is expected of them using the directions below. Pass out equipment to working groups of 3 or 4 students: one Data Collection Sheet, several Macroinvertebrate Keys, and the various plastic containers, spoons, etc. Locate and sort organisms: If the students were not there for the collection of the sample, describe the place and type of habitat where the samples were collected. Provide each group a sample of the collected mud, leaves and water. Have the students look for movement and locate animals in the sample. The students should use a plastic spoon to gently sort similar organisms into the compartments of an ice cube tray or egg carton. Be sure to place stream/pond water into each compartment before sorting. Allow the students to examine the sample and sort macroinvertebrates as long as time allows. Identify organisms and record data: After sorting, each group needs to identify the macroinvertebrates found using the Macroinvertebrate Key and the Data Collection Sheet. If the identified macroinvertebrate is on the data collection sheet, it should be circled. Students should continue to identify their macroinvertebrates and circle those that are on the data collection sheet. Calculate Index Values: Each group now must calculate the index values for each pollution tolerance category on their data collection sheet (Sensitive, Somewhat Sensitive, and Tolerant). For example, if they found three kinds of organisms in the sensitive category, the index value will be 12 (3 species x 4 points = 12). Each kind of macroinvertebrate found and circled will count toward the index value, NOT every individual organism found, unless it represents a different species. For example, if the students find five mayflies (and no other sensitive organisms), the mayflies count as only one kind of organism, and so 1 circled organism x 4 points = an index value of 4 points from the Sensitive category. Record class results: Make a chart on the board of the three pollution tolerance categories: Sensitive, Somewhat Sensitive and Tolerant. Ask each group to record the index values they calculated for each category. (Again, be sure they counted the number of circled kinds of organisms and not the number of individual organisms found.) Add up the groups results and calculate a class average for each pollution tolerance category. If any of the groups numbers vary widely, throw out the outliers or obviously incorrect samples. To determine the water quality rating for that site, add up the averages obtained from each pollution tolerance category to get a total index value. Refer to the chart at the bottom of the data collection sheet to determine whether the water quality of the sample is Excellent, Good, Fair, or Poor. Ask students to return the samples to the collection bucket. Explain to the students that all the samples of water, mud, and animals will be returned to the site of collection. Collect and clean all equipment. Return the samples to the place of collection. Quality & sheds 22

3 Benthic Macroinvertebrate Study continued. Closure: Review the class results and determine the water quality of the body of water. Compare their macroinvertebrate study results with their own personal knowledge of the stream, river, pond or lake. Follow Up: Conduct an evaluation of the same body of water testing for chemical and physical properties (refer to the lesson Quality Monitoring ). Resources: Masterbug Theater: A slide show showing some of the common macroinvertebrates: Online Aquatic Macroinvertebrate Identification Key: Key to Macroinvertebrate Life in the River, The University of Wisconsin, Extension: Aquatic Macroinvertebrates & Quality Resources: 23 Quality & sheds

4 Benthic Macroinvertebrate Study - Data Collection Sheet Benthic Macroinvertebrate Study of Stream/Pond Quality & sheds 24

5 Benthic Macroinvertebrate Study - Key Quality & sheds 25 Developed by the University of Wisconsin-Extension in cooperation with the Wisconsin Department of Natural Resources. Based on a key developed by Riveredge Nature Center, Newburg, WI. May be reproduced with this credit for educational, non-profit purposes. For information, contact UWEX Environmental Resources Center, University of Wisconsin-Extension is an EEO/Affirmative Action employer and provides equal opportunities in employment and programming, including Title IX and ADA requirements. Dragonfly Stonefly Alderfly Dobsonfly Predaceous Diving Damselfly Riffle Pyralid Caterpillar Penny side view of tails Developed by the University of Wisconsin Extension in cooperation with the Wisconsin Department of Natural Resources. Based on a key developed by Riveredge Nature Center, Newburg, WI. May be reproduced with this credit for educational, non-profit purposes. For information, contact UWEX Environmental Resources Center, 608/ University of Wisconsin-Extension is an EEO/Affirmative Action employer and provides equal opportunities in employment and programming, including Title IX and ADA requirements. brown, leatherlike, six legs, usually C -shaped six legs and prolegs on abdomen suction cuplike large body, hinged mouth green, tan, orange or white body lives in stone case lives in stick house dark head, green or tan body, two brush-like tails small, spines on side large mouth parts, spines on side tails long and stiff, long antennas flat gills on abdomen hangs from surface, large mouth parts long tails, gills on abdomen long tails, gills on abdomen large legs, feathery gills plate-like tails, no gills on abdomen Scorpion Ranatra No Obvious Tails One or Two Tails Three Tails Scorpion Nepa Scavenger Predaceous Diving Crayfish Aquatic Sowbug or Isopod Riffle Crawling Whirligig Strider Marsh Treader Giant Bug Backswimmer Boatman Scud or Amphipod No Wings Fishing Spider small, crawls on bottom swims moving hind legs alternating back legs move at same time swims on surface Crawls through water, spotted tan, lives on surface dark, lives on surface grasping front legs, up to three inches swims on back, back white swims right-side-up, back black long breathing tube, grasping front legs long, stick-like Mite -Like, Wings Hard Leathery Wings lobster-like shrimp-like, swims on side walks on bottom tiny, often brightly colored runs on top of water Wings Cyclops or Copepod 10+ Legs Four Pairs of Legs Three Pairs of Legs Seed and Clam Shrimp Flea or Daphnia Rat tailed Maggot Snipe Fly Horse Fly Crane Fly Crane Fly Midge Pupa Black Fly Leech apostropheshaped round swims with a jerk, using antennas Tubifex Flatworm or Planaria Horsehair Pouch Snail Pill or Fingernail Clam Bristle Midge Gilled Snail Orb Snail Freshwater Mussel Nematode or Threadworm long breathing tube two fringed tails smooth, stiff, small head large, grey with tentacles white or grey with tentacles big head, active black, attaches to hard surfaces Limpet Suckers, expands reddish brown, glides along and contracts, body segmented body bottom, body segmented not segmented tan to brown, long body with bristles, no suckers distinct head, small, hair-like, red, green or swims in S shape tan, twists With Tentacles, Brushes or Tails spiral, spiral, opening on left opening on right coiled Legs conical small, whitish, large, 2 to 8 inches, tan or brown dark-colored -Like Microscopic No Legs Single Shell Double Shell Shells No Shells Key to Macroinvertebrate Life in the River (Sizes of illustrations are not proportional.)