Macroinvertebrate Sampling for Water Quality
Macroinvertebrates preserved in vials
Macroinvertebrates in ice cube tray during sampling event
Macro - big enough to see without a microscope
Invertebrate - animal without a backbone
Why?
One easy way we can check the water quality of a stream we are interested in is to sample macroinvertebrates. Macroinvertebrates, or aquatic insects, are either adult or larval insects that live in the stream. Some may bury in the streambed, some might hide under rocks, some might even skate across the water’s surface. Different macroinvertebrates have different tolerances to water pollution. Because of this we can use macroinvertebrate surveys to quickly check the water quality in a stream.
How?
Looking for macroinvertebrates can be as simple as going to your local stream and grabbing a rock and looking to see what is attached to it. It can be as complicated as using gear, such as a kick net or a seine, to try to collect as many macroinvertebrates as possible. In order to check the water quality of your local stream, go to your stream and collect as many macroinvertebrates as possible in a 30 minute time frame. You can do this is just one area, or you can choose multiple sites in the same waterbody to get a better sample. Place the macroinvertebrates in a tub of water to keep them alive. Once you are finished collecting, you can sort similar macroinvertebrates in an ice cube tray or multiple cups, placing similar looking macroinvertebrates together. To identify what you have collected, use a reference such as the Aqua Bugs app by Izaak Walton League of America, Inc. for simple, easy to use identification or visit http://www.aquaticinsects.org/ for more in-depth identification. Once you have identified the aquatic insects you have collected, you can use this Macro Order Level Data Sheet to help to determine the overall water quality of the stream you just sampled. You can also submit macroinvertebrate sampling data to the LGROW Data Repository.