I teach a 9th grade Earth and Environmental Science class. As part of the course, we learn to read the health of a stream. Students are required to look at both the chemical properties and the biological indicators. To determine the health using biological indicators, we search for macroinvertebrates. To help sort our macroinvertebrates, ice cube trays are the perfect tool. They are just the right size for most organisms collected and their white color makes the little buggers easier to identify. If you're interested in assessing the water quality of a stream near you, read on to jump in.
Step 1: What to Look For...
Some organisms have a higher tolerance for pollution than others. If all you find are leeches and mosquito larva, you might want to find a different swimming hole. The biological indicators that you will find in a healthy river ecosystem include mayfly larva, stonefly larva, caddisfly larva, dobsonfly larva, water pennies, and newts. A wide range of these organisms is a good sign. You can find these macroinvertebrates/amphibians by wading into the stream, picking up a rock, and looking closely at the underside. The macroinvertebrates will be clinging to the bottom of the rock to keep from being washed downstream. A good place to look is in a shallow section of the river where the water flows over the rocks quickly (called a riffle). Placing a seine net downstream and turning over rocks just upstream is another way to find larger organisms quickly. You should be able to find and print a key specific to your local waterways.
Step 2: Some Precautions...
Any time you wade into a river, there are inherent risks. Please use caution and common sense. Fast moving water can be dangerous. Slick rocks, storms upstream, unsure footing... please be careful. At the same time, if you're smart enough to use instructables, you're smart enough to get outside and have fun. Don't forget the ice cube trays. A great example of creative misuse!
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