Discovering Didymo Distribution

Citizen Scientists Help Discovering Didymo Distribution Across Alberta


Have you seen rock snot in your local river? Didymosphenia geminata (commonly known as Didymo, or rock snot) is a freshwater diatom that largely goes unnoticed unless vigorous growth occurs, at which time thick mats are produced along stream bottoms. The Discovering Didymo Distribution (D3) project was a collaborative effort to increase the understanding on the distribution of D. geminata across Alberta. The project was a partnership between Trout Unlimited Canada (TUC) and the Jackson Lab at the University of Calgary (U of C), made possible with funding from the Alberta Conservation Association Research Grant Program for the past three years.. The D3 project used a citizen science approach to crowdsource sampling effort and was piloted in Alberta in 2016, with similar efforts taking place at that time in the United States involving Trout Unlimited and North Carolina State University. Volunteers participating in the program were provided sampling kits and instructions on how to collect samples on their own time. In 2017, we created an instructional YouTube video demonstrating how to use the sampling kit and record observations using the Epicollect5 mobile app. Eliminating the need for in-person training sessions. The video helped streamline volunteer training while promoting the project. Volunteers collected samples from all major river basins in Alberta during the three-year program, which were sent to the University of Calgary for microscopy analysis to determine whether or not D. geminata cells were present in each sample. During analyses, samples were categorized as either absent, present, blooming, or misidentified according to the criteria outlined in Table 1.

Table 1. Categorization of samples based on sampler observations and laboratory analysis.

1. Didymo mats were described for field samplers as “feeling rough to the touch much like wet cotton wool. They are generally tightly adhered to the substrate and can form long strings or appear as small tufts”.
2. Misidentified meaning that the suspected Didymo mats observed by field samplers were likely growth of other periphyton species misidentified as Didymo, as no Didymo was present in the sample collected from that site.

2018 Results

Of the 71 samples successfully collected by project participants and analyzed at the University of Calgary during the 2018 sampling season, 47 samples did not contain D. geminata cells, 15 samples contained cells but had no blooms reported by volunteers, and 9 samples both contained cells and had blooms reported (Table 2).

Table 2. 2018 field observations collected by samplers and result of sample analysis.Summary of 2018-2018 Results

During the 2016, 2017, and 2018 sampling seasons, 210 samples were collected and analyzed from 124 waterbodies across the province by 191 volunteers. The Little Red Deer River received the highest sampling effort, with 24 samples being collected over the three sampling seasons. Other water bodies that were commonly sampled included the Red Deer River (n=11), North Saskatchewan River (n=7), Nose Creek (n=6), and Dogpound Creek (n=6). Results of analyses varied between samples collected at individual sites along the same watercourse; e.g. of 8 samples analyzed from sites along the Red Deer River in 2018, D. geminata was absent in 2 samples, present but not reported as blooming in 1 sample, blooming in 4 samples, and misidentified in 1 sample. Sample analysis also showed variation in detections of D. geminata between samples for the same section of watercourse not only between sampling years but also between samples collected at the same site in the same year. For example, D. geminata was detected in only one of three samples collected from the same site on the Little Red Deer River at Twp. Road 332 in 2017. In three samples collected from an approx. 1.5 km reach of the Red Deer River at Sundre, D. geminata was detected in 2004, absent in 2011, and blooming 2017.

For a map of Didymo observations and results of sample analysis following the 2018 season, click here. The web map now features sampling results from the 2016, 2017, 2018 D3 sampling seasons, as well as prior sampling efforts in Alberta and British Columbia by the University of Calgary in 2004, 2009, 2010, 2011, and 2013.


TUC would like to thank all of the volunteers who have dedicated their time and efforts towards the D3 project; we would also like to thank our many project partners who helped in various ways including:

A special thank you to Olds College Water and Applied Sciences instructors David Johnson and Katie King whose students collected a large portion of the samples in 2017 and 2018 all across Alberta, greatly expanding on our knowledge of D. geminata distribution across the country.