Science Article

This investigation uses benthic invertebrates (organisms that live on or in the bottom of a body of water) as a way to determine nutrient enrichment. A measurement of the number and type of these creatures is useful because they remain in the stream for a long period of time and are relatively immobile. As a result, they have to put up with the water quality or die.

Equipment

• cloth window-screen mesh
• 2 meter sticks (yardsticks)
• duct tape
• eyedroppers
• buckets
• tweezers
• magnifying glasses
• field sheets
• pencils
• invertebrate charts

Protocols

For streams, collect the sample at the bottom of the stream in the center of the first riffle. For the ponds, collect the sample in 10- to 25-cm-deep (4- to 10-in) water in the gravel or cobble substrate

Investigation: "Fishing for bugs"

Select a representative 1 sq m (10 sq ft) area in the middle of the channel at the stream or gravel/cobble section of pond.

Have one person place the screen firmly on the bottom of the bed and holds it at a 70° angle so water can pass through it.

Kick 1 sq m of the streambed for 1 minute, then scrape any large particles against the screen for 1 minute. For ponds, this may take some creativity, and a bucket might need to be used to wash/create current to help in the process.

Cradle the contents of the screen and lift them out of the water. Splash the sides to wash the contents to the bottom of the screen.

Pour the contents of the screen into a bucket.

Investigation: "Critter pickin' in the pail"

Stir the mixture in the bucket. Remove some one ladle at a time and place on a white tray. Add clean water to see the bugs.

Pick out bugs one at a time, identify them, and record your findings on the field sheet.

Once 100 bugs have been identified, release all back into the water. If you can't find 100 bugs don't worry—this also says something about water quality.

Record as much information as you can to identify the site for future visits.