Creek Critters as Water Quality Clues

October 09, 2025

OARS River Log | By Heather Conkerton, OARS’ Ecological Restoration Coordinator | Published Oct 9, 2025

If you’ve ever flipped over a rock in a stream and seen tiny bugs, snails, or worms wriggling around, you’ve met the “creek critters” that can tell us a lot about water quality. Scientists call them benthic macroinvertebrates, a fancy term that simply means “small animals without backbones that live on the bottom of rivers and streams.”

Why are they important? Each species has a different tolerance to pollution. Some, like stoneflies and mayflies, need clean, well-oxygenated water to survive. Others, like midges and aquatic worms, can hang on even in more degraded conditions. By looking at which critters are present (and which are missing), we get a clear picture of stream health.

This process is called stream biomonitoring, and it’s a powerful, low-cost way to track water quality over time. Instead of relying only on chemical tests that give a snapshot, macroinvertebrates provide a longer-term record, almost like nature’s water quality report card.

This September, OARS 3 Rivers launched a pilot macroinvertebrate study to test out this approach locally. Our Team members, Heather Conkerton—OARS’ Ecological Restoration Coordinator and Abby McCarthy—OARS’ Water Quality Program Manager, joined by our new TerraCorps Service members, Callie Sties and Grace Bellavance, spent time in the field collecting aquatic critters to send to a lab for identification. Once the results are in, we’ll have a clearer picture of which sampled areas fall into poor, fair, good, or excellent water quality. Combined with our ongoing water quality monitoring, this new data will help us better understand and track the health of our rivers.

OARS’ Water Quality Program Manager Abby McCarthy (left), TerraCorps Service Members Callie Sties (center), and Grace Bellavance (right) collect macroinvertebrate samples during OARS’ pilot stream biomonitoring study—using “creek critters” to reveal the health of our rivers.

The pilot was a success, and OARS hopes to expand macroinvertebrate monitoring in the future. Not only does this data help guide restoration and protection efforts, but it’s also a fun and hands-on way to connect with local rivers and streams.

So, the next time you see a stonefly clinging to a rock, know that these little critters are doing big work. They are helping us understand and protect the health of our rivers.

Website resource (https://www.macroinvertebrates.org/)

River Log

~30%

of the SuAsCo rivers watershed is wetlands, crucial for wildlife habitat and water quality

~30%

of water samples in the SuAsCo rivers watershed contain PFAS, leading to increased monitoring and remediation by local authorities and environmental groups

~70%

of dams in the SuAsCo watershed are over a century old, requiring extensive upkeep and presenting obstacles to river restoration and fish passage

>40%

of the land within the watershed is publicly accessible, offering recreational opportunities such as hiking, boating, and birdwatching to the community

~15%

of the land in the SuAsCo rivers watershed is covered by impervious surfaces such as roads, rooftops, and parking lots. This contributes to stormwater runoff and water pollution issues

>40%

of the land within the Sudbury, Assabet, and Concord rivers watershed is publicly accessible, providing endless opportunities for paddling, hiking, and wildlife exploration.

Creek Critters as Water Quality Clues

OARS River Log | By Heather Conkerton, OARS’ Ecological Restoration Coordinator | Published Oct 9, 2025