Sometimes the most overlooked beings have the biggest stories to tell. Bioindicators are organisms such as plants, animals, bacteria, and more that can be used to assess the health of a natural ecosystem. By monitoring bioindicators, we can better understand the changes taking place in our environment. The presence or absence of certain organisms can provide an indication of the health of the environment based on their sensitivity to pollutants, habitat degradation, or shifts in food webs.  

Macroinvertebrates are small aquatic animals visible to the eye that can be found suspended in the water column, attached to submerged objects such as rocks, logs, and sticks, or burrowed into the sediments at the bottom of the aquatic environment (in the benthos). These critters are the building blocks of aquatic life and are an essential food source to many other animals like fish. There are several distinct categories of macroinvertebrates, including beetles, worms, snails, as well as mayfly, dragonfly, damselfly, and caddisfly larvae/nymphs. In healthy aquatic environments, there can be hundreds of different species of macroinvertebrates present.

Macroinvertebrates are an important and commonly measured bioindicator as diversity, evenness and species richness indexes can be calculated to indicate water health and quality.  Many macroinvertebrates are sensitive to water contamination and pollution, so by surveying and identifying the macroinvertebrates present in a water body, scientists can understand the stability and health of the environment along with biological reactions to pollution and other conditional changes. Due to increasing concern of water contamination, Environment and Climate Change Canada (ECCC) has developed the Canadian Aquatic Biomonitoring Network (CABIN), a protocol that outlines macroinvertebrate collection procedures for different aquatic habitats to monitor water quality. 

Agricultural runoff is a major source of aquatic pollution that can affect water quality. The excess nutrients that flow into water systems can trigger toxic algal or bacterial blooms that can harm surrounding species. PWA monitors water quality and bacteria such as E. Coli and Coliform are some of our measurable parameters that we test in our lab to determine if the concentrations of bacteria are hazardous or not. In partnership with the Agricultural Alliance of New Brunswick and RBC, the PWA placed ‘benthic bags’ in the Petitcodiac River and one of its tributaries to test the effectiveness of various anti-run-off measures. These benthic bags each contain rocks that are colonized by macroinvertebrates over the season. Ideally, the bags downstream of the runoff treatment program will be colonized by more pollution-sensitive species than the control bags upstream of the treatment area. 

PWA Benthic Bag Collection  

Freshwater mussels are also considered a bioindicator as they too are sensitive to pollution and habitat degradation. The presence of native freshwater mussels indicates a healthy environment because they improve water quality by filter feeding and accumulating and storing toxins, but only at a certain threshold, so excess toxins and pollutants pose a threat to them. PWA has surveyed and monitored different freshwater mussel species and populations since 2018, encountering 6 different species across 66 sites. One of the species, the Brook Floater, is particularly sensitive to pollution and has become a species of special concern under the Species at Risk Act (SARA). 

Brook Floater 

To enter our giveaway, post a picture of a bioindicator, post it, tag us, and use #25watershedmoments. 

Atlas of Common Freshwater Macroinvertebrates of Eastern North America. 

Canada, E. and C. C. (2017). Water: CABIN. 

Environment and Climate Change Canada. (2018). Cabin Wetland Macroinvertebrate Protocol. 

Ghosh, D. D., & Biswas, J. (2015). Macroinvertebrate diversity indices: A quantitative bioassessment of ecological health status of an oxbow lake in Eastern India. J Adv Environ Health Res, J Adv Environ Health Res. 

Manickavasagam, S., Sudhan, C., Bharathi, & Aanand, S. (2019). BIOINDICATORS IN AQUATIC ENVIRONMENT AND THEIR SIGNIFICANCE – ProQuest. 

McQuaid, B. Watershed Science Institute.