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Benthic Invertebrates in the Headwaters of the Athabasca Watershed
AWC-WPAC, Friday Read, Project Update, and Science | aquatic invertebrates, biomonitoring, CABIN, Gregg River, McLeod River, Solomon Creek, and Whitehorse Creek | April 2022

Ashley Johnson, Education and Outreach Coordinator

Missed our benthic invertebrates webinar? Don’t worry! This blog post will tell you all you need to know about our project update on benthic invertebrates in the headwaters of the Athabasca watershed. 

First of all, what is a benthic invertebrate? 

  • Benthic is a term used to refer to anything living on the bottom of a body of water, while invertebrates are critters without a spine. So, benthic invertebrates can be bugs, larvae, or other critters living on the bottom of our rivers, lakes and streams. 
Illustration of a stonefly larvae.

Why are we collecting benthic invertebrates? How can we use aquatic organisms to monitor the health of aquatic ecosystems? 

  • Benthic invertebrates are a good indicator of water quality and ecosystem health, as well as being a food supply to species at risk. 
  • They are in-situ biomonitors. Mayflies may have a short lifespan, but their larvae can be in the watershed for 1 to 2 years, and stonefly larvae can be in the watershed for 2 years or more! 
  • We initiated this project in May of 2020, to address some of the data gaps around our knowledge of benthic invertebrates of the headwaters of the Athabasca watershed. 

The project is part of the Eastern Slopes Collaborative, an initiative led by Living Lakes Canada in collaboration with many other organizations. The goal is to collect data across the eastern slopes of the Rocky Mountains using a standard protocol for data collection: CABIN.

CABIN, or the Canadian Aquatic Biomonitoring Network, is a standard sampling protocol that we used to take samples of benthic invertebrates across 4 different sites in 2021. Standardized sampling allows us to be able to compare results between watersheds, and over time. Some of the samples went to a taxonomist to be identified, while others were sent to an eDNA analysis lab, for an initiative called STREAM (Sequencing the Rivers for Environmental Assessment and Monitoring). Read more about our site selection and sampling here and here.

CABIN Fieldwork by AWC Staff.

In the field, the main steps are: 

  • A primary site assessment, looking at land use, and taking note of where samples will be taken 
  • A habitat assessment, looking at riffles, canopy coverage, and stream-side vegetation 
  • Water quality sampling 
  • Collecting channel data 
  • Conducting a pebble count 
  • Kick-netting (the collection of samples to be sent for analysis). This is 3 minutes of sampling mayhem, where the aim is to zig-zag across the stream in order to sample all the different microhabitats and their inhabitants. 

Types of Benthic Invertebrates: 

Glossosoma – might be captured in eDNA, but some species aren’t in an identifiable life-stage when CABIN sampling occurs. 

Ephemeroptera ‘Mayflies’ – Canada-wide, 21 families, 82 genera, 335 valid species known across Canada, with 66 species undescribed or not recorded in Canada. Taxonomy is a bit of a mess—constantly changing. In Alberta, there are currently 17 families, 63 genera, and at least 148 species.  

Plecoptera ‘Stoneflies’ – Canada-wide, 9 families, 79 genera, 267 species, with 34 species likely undescribed/unrecorded from Canada. In Alberta, there are 9 families, 59 genera, and 125 species. 

Tricoptera ‘Caddisflies’ – Canada-wide, 25 families, 636 species, with 129-181 species likely undescribed/unrecorded from Canada. In Alberta, there are 17 families, 77 genera, and 277 species. A subset of Tricoptera includes Apatanids (Apatania) – 6 species known in Alberta. Usually associated with spring streams and further north in lakes. One species occurs as far north as Ellesmere Island! They have a tolerance value of 3. 

Chironomidae ‘non-biting midges’ – 798 described species known in Canada, but at least another 1000 species are expected to exist as well. In Alberta, there are at least 149 genera, and probably 500-600 species.  

Of these bugs, the ones that are most important for assessing the health of the sites are: 

  • EPT taxa: Ephemoptera (mayflies), Plectoptera (stoneflies) and Trichoptera (caddisflies): These 3 taxa are very sensitive to pollution 
  • Chironomids: This group is not sensitive to pollution 

But how can we evaluate the health of sites using these bugs?  

There are a number of different metrics that can be used, and they fall into 4 categories: abundance/richness measures, composition measures, tolerance measures, and trophic/habitat measures. 

Abundance/richness measures: 

  • Total abundance: the total number of bugs collected. A higher number indicates a more productive run of a river, but disturbance can also dramatically increase the populations of invertebrates that thrive in those conditions. 
  • Richness: the number of unique taxa per site (in other words, the number of different types of bugs collected). A higher richness means a less disturbed site.  
In this made-up sample, the total abundance is 10, and the richness is 3.
  • Shannon-Wiener Diversity Index: This number is calculated using species richness, and evenness (the total number of taxa and whether they’re in equal proportion). The closer the number is to 0, the lower the diversity (which generally indicates a less healthy area) 

Composition measures: 

  • % Chironomids: a higher percentage indicates poor water quality. Chironomids are typically tolerant of organic pollutants such as low oxygen, and/or high levels of nutrients and silt. So, when there are more chironomids, it is likely because less pollution-tolerant critters can’t survive there.  
  • % Dominant taxa: Having a higher % dominant taxon indicates poor water quality. If one type of organism is dominating a sample, it usually indicates that there is something limiting other species from being successful. 
  • # EPT (Ephemeroptera, Plecoptera, Tricoptera) Taxa: A high number of EPT taxa indicates a healthy site. 
  • % EPT (Ephemeroptera, Plecoptera, Tricoptera): a high % EPT indicates a healthy site, because these taxa don’t handle pollution well. 

Tolerance measures: 

  • Hilsenhoff biotic index: This index evaluates the tolerance of all taxa to organic pollution, while factoring in the number of specimens, to provide a single average tolerance value for the organisms in an aquatic environment. The tolerance value is a number from 0 to 10, where 0 indicates excellent water quality, and 10 indicates severe pollution. 
  • Hilsenhoff family biotic index: Family level specimen observations are included. This usually results in a higher tolerance level, because there are generally taxa in a family who are more resistant to pollution, resulting in a higher tolerance at the family level. 

Trophic/habitat measures: 

  • % Shredders: A higher percentage reflects more carbon recycling. This value is very sensitive to riparian zone impairment. 

From being out in the field, we had expected Whitehorse Creek to have the best water quality, followed by either Gregg River or McLeod River, and lastly Solomon Creek. To make things simple, I’ll rank them from one to four, with one generally being the highest, and four being the lowest (unless otherwise stated). 

Here are the actual results:  

McLeod River: 

  • Abundance: 4 
  • Richness: 2 
  • Shannon-Wiener Index: 2 
  • % Chironomids: 4 
  • % Dominant Taxa: 4 
  • # EPT: 1 
  • % EPT: 2 
  • Hilsenhoff Family: 1 (lowest, which indicates excellent water quality) 
  • Hilsenhoff: 1 
  • % Shredders: 4 

Whitehorse Creek: 

  • Abundance: 1 
  • Richness: 4 
  • Shannon-Wiener Index: 4 
  • % Chironomids: 2 
  • % Dominant Taxa: 1 (this is not a metric you want to win!) 
  • # EPT: tied with Gregg River 
  • % EPT: 1 (while this looks good, it’s because there’s one taxon dominating the sample) 
  • Hilsenhoff Family: 2 
  • Hilsenhoff: 2 
  • % Shredders: 2 

Gregg River:  

  • Abundance: 3 
  • Richness: 1 
  • Shannon-Wiener Index: 3 
  • % Chironomids: 3 
  • % Dominant Taxa: 2 
  • # EPT: tied with Whitehorse Creek 
  • % EPT: 3 
  • Hilsenhoff Family: 3 
  • Hilsenhoff: 3 
  • % Shredders: 3 

Solomon Creek: 

  • Abundance: 2 
  • Richness: 3 
  • Shannon-Wiener Index: 1 
  • % Chironomids: 1 (this is not a metric where coming in 1st is a good thing!) 
  • % Dominant Taxa: 3  
  • # EPT: 4 
  • % EPT: 4 
  • Hilsenhoff Family: 4 
  • Hilsenhoff: 4 
  • % Shredders: 1 

So, what does that all mean? Basically, McLeod River was our best site when it comes to water-quality, which was an unexpected result for us. We’re super excited to have successfully completed our first year of sampling, and can’t wait to get out in the upcoming field season!