Collecting Aquatic Insects to Determine Water Quality

Matt Cybulski taking a Benthic sample at Biggar Creek. (Photo by  Nicole McGregor, Assistant Environment Officer)

Many people may not realize it, but aquatic insects are present in all waterbodies and many flying insects actually spend most of their lives living underwater in streams, rivers and lakes before emerging as adults.

Common flying insects such as mosquitoes, blackflies, mayflies and dragonflies hatch, develop and live underwater before metamorphosing into flying adults. Dragonflies can actually spend several years living as a nymph underwater and like all the other flies previously mentioned, the underwater nymphs look nothing like they do when they are adults.

One interesting application of these aquatic invertebrates is that they can be used to indirectly determine water quality using a method referred to as Aquatic Invertebrate Biomonitoring.

The primary reason insects are often used as indicators of aquatic ecosystem health, and thus water quality, is that many species are sensitive to pollution and sudden changes in their environment.

Other reasons include the fact that aquatic insects are sedentary (they don’t move very far), and that they are long lived (some up to three years). If sensitive species are found at pristine reference sites but are not found at a morphologically-similar test site, this would indicate that the test site has experienced some form of environmental stress that caused the loss of the sensitive species.

Earlier this September, Garrison Petawawa Env Svcs conducted aquatic invertebrate sampling at test sites within the Range and Training Area as well as pristine reference sites within the Petawawa Research Forest and Algonquin Provincial Park to compare them to.

Once specialized taxonomists identify all of the species that were collected, statistical methods will be used to determine if the species found within the test sites are different from the species found in the pristine reference sites.

The results will ultimately help to determine whether activities within particular areas of the RTA have an effect on water quality and aquatic ecosystem health.