Aquatic Macroinvertebrates are Signallers of Water Quality
Aquatic macroinvertebrates signal to us the quality of our waterways. From our local watershed to our rivers, these small animals and larval stages of insects can be seen without a microscope; they play a large part in our freshwater ecosystem, recycling nutrients and providing food to fish and other higher-level aquatic animals.
There are many resources available when it comes to learning about how to conserve, preserve, and protect nature and how to share what we have learned.
Recently, we participated in a program led by the Department of Conservation and Natural Resources (DCNR) called “Canaries of the Stream.” In the same manner aquatic macroinvertebrates signal water quality, canaries are signallers of air quality and are often used to detect air quality in coal mines.
Our tour leaders, comprised of university interns and DCNR educators, led us to a high-elevation tributary cold stream to learn about aquatic macroinvertebrates. We studied how they indicate the health of this particular area that makes its way to the Youghiogheny River. Tools supplied by the DCNR for our aquatic expedition included a large net to collect sediment from the top, middle, and bottom of the stream, tweezers, three trays to which stream water was added in each, an identification poster, and a marker to record what we found in the water. Once we filtered the stream water through the netting, organic matter and aquatic macro-invertebrates were taken to the shoreline to identify. Right away, the most noticeable was a good-sized crustacean resembling a miniature lobster, known to us as a crayfish. We quickly released it back into the shallow rocky water.
Aquatic ecologists have categorized species of aquatic macroinvertebrates into four functional feeding groups (Cummins 1973).
- Shredders such as Caddisflies and Stoneflies process organic small decaying matter such as leaves, debris, and other vegetation in the water.
- Collectors that include Beetles and Dipteran (true flies) filter and accumulate even smaller pieces of organic matter found in the water column and bottom sediment.
- Grazers are found on rocks and woody debris. Imagine Caddisflies and Beetles grazing on other aquatic insects, Periphyton, Detritus, and submerged aquatic plants.
- Predators, like Dragonflies, prey on dead animal material in the water.
Once our eyes adjusted to seeing the tiny animals moving in the sediment, we used tweezers to move the specimen into the trays.
We used the Key to Macroinvertebrate Life identification chart to identify and circle what we had seen. We identified the following: Cranefly Larva, Lobster-like Crayfish, Water Penny, several Caddisfly Larva living on the bottom of a rock submerged in the stream bed, Caddisfly Larva, Dobsonfly or Fishfly Larva, Stonefly Nymph, and Mayfly Nymph.
After releasing the aquatic macroinvertebrates back into the water, we categorized and allocated a number for each specimen identified and their tolerance level.
Water quality is identified in three groups; tolerant, fresh, and sensitive to pollution tolerance/intolerance. Based on the Aquatic macro-invertebrate water quality benchmark chart below, our total score was 24 indicating excellent water quality.
- Excellent (score of >22 or at least 4 “S” taxa*)
- Good (score of >17-22 or at least 2 “S” taxa)
- Fair (score of 11-16 or at least 1 “S” * taxon)
- Poor (score of <11 or at least no “S” taxa)
We recommend participating in biodiverse nature and ecology programs led by DCNR in your national, state, and local conservation and protected areas. These interesting educational programs, often free, open eyes to a whole new world, the importance of biodiversity, friends, and maybe even a new opportunity.
*Taxa: plural noun of Taxon
Taxon: used in the science of biological classification, a group of any rank, such as species, family, or class seen by taxonomists to form a unit.