You know a little about how to monitor water quality. But not everyone is interested in all that "chemistry stuff." How about learning a really fun way to determine whether a stream or pond has clean water?
When your parents go to buy a new house, they generally want to know a little about the neighborhood before spending all that money. That only makes sense. One of the best ways to tell whether or not the neighborhood is a good or safe place to live is to talk to people who already live there. You may not be able to talk to the "residents" of a water body, but who (what species) you find there can tell you a lot about the quality of their aquatic "neighborhood."
When you think of the animals that live in streams or ponds, you probably think of fish, turtles and frogs. But as you will remember from the discussion of aquatic ecosystems, there are plants and smaller "critters" in water bodies that provide food for these larger animals. It is these tiny animals, which we call invertebrates, that can reveal a lot of information about water quality. Invertebrates are animals that lack backbones. Aquatic insects, crayfish and freshwater mussels are common invertebrates found in ponds and streams. Because most of these species can be seen with the naked eye, they are called macroinvertebrates.
Different macroinvertebrate species can tolerate different levels of water quality. Mayfly nymphs require very clean water. Mosquito larvae, on the other hand, can exist in quite dirty water. If you do a macroinvertebrate survey of a stream and find many species that are intolerant to pollution, then the chances are the water is clean. On the other hand, if you find mostly species that do well in polluted water, and no intolerant species, the stream may be polluted.
You probably remember from an earlier article that one sign of a healthy aquatic ecosystem is the variety or diversity of plant and animal life that lives there. Generally, the greater the diversity, the healthier the habitat. Because macroinvertebrates can indicate the health of an aquatic ecosystem, we call them biological indicators or bioindicators. Bioindicators are a very important part of water quality monitoring.
So how do you go about collecting macroinvertebrates from a stream? Kick seining is a good technique for collecting the little critters. It involves stepping into the water, facing downstream, and kicking the stream bottom with your feet. This dislodges the macroinvertebrates, which then are carried by the current downstream and (hopefully) into your net. Kick seining should only be done in safe water conditions and always with an adult present.