Benthic Macroinvertebrates

Benthic macroinvertebrates are small organisms that live on the bottom of streams, rivers, and lakes. They are useful as water quality indicators because they have relatively long lifespans and are sensitive to changes in the aquatic environment.

What Are We Monitoring?

Benthic macroinvertebrates can include insects, worms, mollusks, and crustaceans. Toronto and Region Conservation Authority (TRCA) collects benthic macroinvertebrates annually at more than 150 monitoring stations across the Toronto region.

Each invertebrate is identified to the species or family level.

In 2022, TRCA collected and identified more than 50,000 benthic macroinvertebrates to monitor the health of aquatic ecosystems in regional watersheds.

TRCA team members collect benthic macroinvertebrates to monitor the health of aquatic ecosystems in regional watersheds
TRCA monitoring field staff collect benthic macroinvertebrates in a local stream

Benthos data are collected in support of the long-term Regional Watershed Monitoring Program.

Data are also collected to support research studies, assess the impacts of development projects, evaluate habitat restoration projects, and guide environmental assessments.

Visit TRCA’s Open Data Portal to access the last 10 years of benthos data collected in TRCA’s nine watersheds.


What Are The Data Telling Us?

Benthic invertebrate communities remain stable in the majority of watersheds in the Toronto region.

The healthiest benthos communities are found in the headwater regions of the larger watersheds, while declines in benthos communities are more noticeable in smaller and more urbanized watersheds, such as Highland Creek.

Good news! Some sensitive benthos populations persist in the heavily urbanized Don River watershed, highlighting the importance and potential of continued conservation and restoration efforts.

Select the image below to view the Benthic Communities in Streams dashboard.

TRCA Watershed Reporting Hub Benthic Communities in Streams dashboard

Visit TRCA’s Watershed & Ecosystems Reporting Hub

Monitoring Benthics: Technical Training

Members of TRCA’s aquatic monitoring team are provincial leaders in identifying benthic macroinvertebrates, with staff certified in genus level identification by the Society for Freshwater Science.

The TRCA aquatic monitoring team are provincial leaders in identifying benthic macroinvertebrates

TRCA offers external training to environmental professionals in Ontario Benthos Biomonitoring Network (OBBN) standardized sampling protocols.

OBBN is a multi-sector biomonitoring collaboration, led by the Ontario Ministry of the Environment, Conservation and Parks, that allows members to share their data through a centralized database.



TRCA Watershed Planning and Ecosystem Science: