Macro-invertebrates

Macroinvertebrates are all the animals without backbones we can see with our naked eye in our streams. Some of us look at these organisms and think how interesting they are, others want nothing to do with them. Whatever your thoughts may be, these critters can give us a good idea of how clean the stream is. 

Some of these animals like the mayfly nymph and the water penny nymph are great indicators. These organisms are sensitive to changes in the quality of the water.  If you can find these many of these organisms in a stream, chances are that stream is healthy. They are sensitive to changes in the quality of the water.

Other animals like the cranefly larvae, hellgrammites, and fishfly larvae are somewhat sensitive to changes in water quality.  These organisms are somewhat sensitive to changes in the quality of the water.  This means that finding a great number of these organisms in a stream can tell us that the stream is fairly healthy.

Finally, there are those organisms that can tolerate a great change in the quality of the water. These organisms can live in clean unpolluted water, or they can live in water that have pollutants and possibly some harmful things in the water. Organisms like the flatworm, leech, crayfish, and black flies can tolerate changes in the water.  These organisms are tolerant of changes in water quality.  

Keep in Mind

As you look for oranisms in your local streams, also remember that finding a wide variety of organisms also can help you determine the quality of the water. If there is a greater biodiversity (different forms of life) then it is likely that the stream is healthy. If you find many organisms, but they are all of the same type then the quality of the water could be poor. Click here for an Excel spreadsheet that calculates the quality of the water based on the organisms found there.