The Nottawasaga Valley Conservation Authority


What is Biomonitoring?

The Biomonitoring program samples benthic macroinvertebrates to measure stream health.

What are benthic macroinvertebrates?

Benthic macroinvertebrates are aquatic “bugs” that live on the bottom of a stream, river or lake. Aquatic worms, insects and crustaceans make up the bulk of our benthic macroinvertebrate samples.

Why do we monitor benthic macroinvertebrates?

Conventional water quality sampling consists of sampling at a specific point in time (that few minutes that it takes to collect a sample). Although this sampling provides great information for the specific time sampled, it does not necessarily tell us what is happening in the stream over the remainder of the year.

Benthic invertebrates live in a stream for up to three years. During this time, they are exposed to the full range of water quality conditions present in the stream. Some species require excellent water quality to survive while others are quite tolerant of pollution. By looking at the different species present at a sampling site, we can identify whether stream health is good, fair or poor.

Monitoring of benthic invertebrates allows us to answer several important questions: “Is development impacting stream health?” “Are our streams becoming healthier or more degraded over time?” “Where will our stewardship activities be most effective?” “Are our stewardship activities resulting in water quality improvements?”

How are benthic macroinvertebrates sampled?

These organisms are collected from fast and slow water areas at each site using a “D-frame” dip net or similar sampling device. They are preserved and brought back to our lab for sorting, identification and analysis.

Where do we monitor benthic macroinvertebrates?

Approximately 75 sites are sampled each year within the watershed. Half of these sites monitor potential development or wastewater treatment plant impacts. The majority of other sites are focused on long-term monitoring. Two of our ten subwatersheds are monitored each year so that we cover our entire watershed every five years. We also assist our Land and Water Stewardship Services department to monitor the effectiveness of stewardship projects.

What results are we seeing?

  • Unhealthy streams (i.e. Innisfil Creek subwatershed) are often associated with intensive agricultural land use, sparse riparian cover and lack of forest cover

  • Healthy streams are associated with a high percentage of forest cover within their drainage area and with wide forested buffers next to the streams themselves

  • Ponds constructed within stream systems can result in local impacts to stream health

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