Stream Quality and Macroinvertebrates

South Inlet of Raquette Lake

Yes, the stream is beautiful, but how can we ensure it will be as beautiful in the future? It is possible to monitor the quality of stream water by studying the macroinvertebrate life which inhabits the stream.

Specific groups of invertebrates are sensitive to pollution. Other groups are able to thrive in polluted water. Using a sampling technique, biologists are able to examine the diversity of aquatic life to get an indication of the health of the stream.

The South Inlet of Raquette Lake was studied using this technique. Groups of invertebrate found there are highlighted. You may click on these links to see images for identification.

Aquatic Macroinvertebrate Identification Key
This web site provides an excellent, easy to follow dichotomous key for identification of your samples.

Materials

Each group of students will need

Sampling Procedure

  1. Identify the transect of the stream to be sampled. The transect should cross the stream and be a few feet wide.
  2. One student will hold the collection net on the bottom of the stream.
  3. Other students will rub the rocks a foot or two in front of the net. As algae and invertebrates are loosened from the rocks, the water current will wash them into the net.
  4. Place the invertebrates into the bucket. Make sure there is a bit of water in the bucket
  5. Continue across the stream until you have completed at least one full transect.
  6. After the transect has been completed, sort your invertebrates into groups and identify them. You may use the ice cube trays to separate the groups.
  7. Tally the number of identified individuals. Use the tables provided for your tallies
  8. When all have been identified and counted, release the invertebrates back into the stream.

Data Tables

Group One Taxa
Invertebrates Very Sensitive to Pollutiontally
StoneflyOrder: Plecoptera
CaddisflyOrder: Trichoptera
WaterpennyOrder: Colepotera
Riffle BettleOrder: Coleoptera
Mayfly LarvaOrder: Ephemeroptera
Gilled SnailOrder: Gastropoda
Dobsonfly Larva
Hellgrammite		Order: Corydalidae
PlanarianPhylum: Platyhelminthes


Group Two Taxa
Invertebrates Somewhat Pollution Toleranttally
CrayfishOrder: Decopoda
SowbugOrder: Isopoda
ScudOrder: Amphipoda
Alderfly LarvaOrder: Sialidae
Fishfly LarvaOrder: Corydalidae
Damselfly LarvaOrder: Odonata
Suborder: Zygoptera
Watersnipe Fly LarvaFamily: Athericidae
Crane Fly LarvaSuborder: Nematocera
Beetle LarvaOrder: Coleoptera
Dragonfly LarvaOrder: Odonata
Suborder: Anisoptera
ClamClass: Bivalvia


Group Three Taxa
Pollution Tolerant Invertebratestally
Aquatic WormClass: Oligochaeta
Midge Fly LarvaSuborder: Nematocera
Black Fly LarvaFamily: Simulidae
LeechOrder: Hirudinea
Pouch Snail
Pond Snail		Class: Gastropoda
Other SnailsClass: Gastropoda

Questions for Exploration

  1. Complete the following chart based on the data you collected to determine the water quality index for your stream.


    2. Water Quality Index based on Biological Inventory
    Level of Pollution ToleranceNumber of Invertebrate Types
    (N)    		Scoring Value
    (SV)    		Group Score
    (N x SV)
    Very Sensitive3
    Somewhat Sensitive2
    Tolerant1
    XXXXXXXXXXSummation =
    Interpretations of Water Quality Index
    Excellent > 22
    Good17-22
    Fair11-16
    Poor< 11



  2. Based on your Invertebrate Sampling Data and the Water Quality Index, what is your determination regarding the quality of the stream? Explain how you came to this conclusion.

Websites and Equipment

Pathfinder Science
Want more environmental study ideas? Click on the link for just about everything under the sun.

Pensylvannia Watersheds
At this site you can gain access to several suppliers of water monitoring equipment.