Benthic Macroinvertebrates
Benthics Monitoring: Indicators of Environmental Health
Benthic macroinvertebrates are a community of organisms that live in the substrate (or benthos) found at the bottom of creeks, streams, rivers, lakes and wetlands. This interesting group of animals are generally large enough to see with the naked eye (macro), spend at least some portion of their life in an aquatic environment, and are all without backbones (invertebrate).
Typical benthic invertebrates are animals such as snails, crayfish, clams, leeches, worms and the larval stages of insects like dragonflies, mayflies, stoneflies and beetles that spend some or all of their lives in water. What makes these animals so interesting is that the health of a watercourse can be determined from the number and types of organisms found in the benthic samples!
- Some benthic organisms, such as mayflies, stoneflies and caddisflies are very sensitive to pollution. Finding these organisms in our samples is a good indicator of a healthy environment.
- Some benthic critters are tolerant of pollution , such as worms, leeches and chironomids. Finding these organisms in our samples is a good indication that the environment is being negatively impacted by pollution.
- Healthy rivers, creeks and streams will also have a large population of benthic macroinvertebrates with high species diversity—meaning that there is a large variety of critters to be found within the bottom muck.
KCCA operates a benthic monitoring program in the fall that follows a provincial protocol for sampling in creeks and streams. Analyzing the benthic community along with collecting surface water chemistry data provides information on the health of the watercourse. Over time, trends and patterns of the data can be studied and water quality issues can be addressed by using best management practices in areas of concern.
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Benthic invertebrate samples are collected according to the Ontario Benthos Biomonitoring Network protocol, whereby a “kick and sweep” sample is taken using a D-net across two different riffle transects in a stream segment. Each sample is sorted in the KCCA wet lab and individual specimens are identified to family level. The relative health of the watercourse can be determined from the number and types of organisms found in the samples.