If you know how to find them, the creatures that live in a lake’s shallow water — leeches, mayfly nymphs, stonefly larvae and more — are valuable clues to a lake’s health.

U-Link’s first free public training program on monitoring benthic macroinvertebrates – creatures with no backbone that you can see without a microscope – wrapped up on July 18.

“We look at those species, and we look at the types of habitats they typically live in,” explained Brendan Martin, U-Link’s Environmental Program Coordinator.

“They’re an integral part of the aquatic ecosystem.”

The program was made possible through the Great Lakes Local Action Fund, a provincial grant. Martin said they hope to reapply for funding to train more citizen scientists how to sample and monitor these tiny creatures.

By monitoring the amount of macroinvertebrates they find in the shallow waters around the County’s lakes, U-Links gains insight into the area’s recent history. They also test for the electrical conductivity of the water, and the oxygen levels to get a sense of the health of the lake.

“It’s not a substitute [for water testing] — but it works very well with that data,” he explained.

U-Links returns to each spot they sample multiple times. Through comparing data, they can chart a lake’s history.

“These [species] are constantly in contact with the water, and if there’s, say, an algae bloom immediately after the ice goes out, that could impact the population of dragonflies,” Martin said.

Many of these creatures are staples in the diet of turtles and fish: if macroinvertebrates are under threat, that could impact fishing and recreation activities.

“Keeping tabs on how their populations are changing over time are very important for these industries,” Martin said.

At the in-person demonstration at Halls Lake, Martin showed attendees how to operate the specialized D-net, disturbing sand and pebbles to scoop up samples of the lake’s benthic population.

The group later sifted through the samples, collected in containers on the shore.

The training program also focused on how to report which creatures are found, marking the type of ecosystem and location of each sample.

Around the world, benthic macroinvertebrate monitoring has been used as a marker of lake health since the 1980s. In Ontario, it’s been common practice since the early 2000s.

Now climate change presents an everincreasing threat to the health of lakes, and the benthic macroinvertebrates U-links tests for.

“As temperatures rise, you lose the dissolved oxygen,” said Martin. “That decreases the ability for these organisms to function on a day-to-day basis.”

For more information on upcoming workshops and opportunities to get involved, visit ulinks.ca

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