Photo: © Environment Canada 2010

Aquatic Biological Monitoring

Aquatic biomonitoring measures changes in biological communities (for example, fish, benthic macroinvertebrates, and algae) in order to assess the health of aquatic ecosystems. Biomonitoring is complementary to traditional physical and chemical monitoring. Biological monitoring can measure impacts of cumulative stressors in the aquatic environment including impacts from chemical interactions, contaminant pulses, or unknown contaminants that are difficult to capture with routine chemical sampling.  Other stressors that may be captured by biological monitoring include the presence of exotic species, habitat degradation in the water body or surrounding land, climate change, and fluctuations in water quantity.

Biological Indicators

Many types of organisms can be used for biomonitoring including benthic macroinvertebrates, macrophytes, algae, zooplankton and fish. These organisms are sensitive to a variety of disturbances and are recognized as environmental indicators. Currently, CABIN uses benthic macroinvertebrate communities to assess fresh water ecosystem health.

Benthic macroinvertebrates or, bottom dwelling animals without backbones, live in all freshwater ecosystems. This group includes the larval stages of many insects such as mayflies, dragonflies, mosquitoes as well as other animals such as worms and mites.

Many biomonitoring programs, including CABIN use benthic macroinvertebrates to evaluate aquatic conditions.

Advantages of using benthic macroinvertebrates:

  • Reflect site-specific impacts
  • Reflect cumulative impacts
  • Respond to a wide range of stressors
  • Ubiquitous in the aquatic environment
  • Key part of food web
  • Protocols are well developed

Reference Condition Approach

CABIN employs the Reference Condition Approach (RCA) as the principal method for site assessments. RCA study design begins with the identification of a priority area or region of concern, based on hydrological (basin, sub-basin) or biogeographic (ecozone, ecoregion) boundaries. Reference sites are then selected where anthropogenic effects are minimal. A bioassessment model is developed from the reference site data. This model defines the range of biological communities that should be found at a site if the site is not affected by human activities.

Potentially impaired (or test) sites are assessed against reference sites using the bioassessment model. The divergence between the benthic macroinvertebrate communities at reference sites and a test site indicate the extent of potential impairment.


A set of national CABIN protocols have been produced and outline the standardization of field collection, laboratory work, and analysis of biological monitoring data as part of the CABIN program. Other supporting documents include field sheets and field equipment checklists. Reports by outside agencies using CABIN methodology and scientific journal articles provide additional information.

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