INVASIVE SPECIES SURVEY: DIDYMO 2014

Prepared by: Heather E Milligan

December 2015 INVASIVE SPECIES SURVEY: DIDYMO ALGAE 2014

Yukon Department of Environment Fish and Wildlife Branch SR-15-01

Acknowledgements Shailyn Drukis, Ella Parker, Aven Knutson, Nigel Eckert, and Dennison Bohmer conducted fieldwork in 2014. Shailyn entered data and Aven Knutson identified didymo by microscope. Oliver Barker conducted fieldwork in 2010. Gerry Whitley, Bruce Bennett, Andrea Altherr, Aaron Foos, Lloyd Freese, and Dan Greenberg submitted samples.

Cover Photo: Carpenter Creek with didymo present. Photo taken by Aaron Foos.

© 2015 Yukon Department of Environment

Copies available from: Yukon Department of Environment Fish and Wildlife Branch, V-5 Box 2703, Whitehorse, Yukon Y1A 2C6 Phone (867) 667-5721, Fax (867) 393-6263 Email: [email protected]

Also available online at www.env.gov.yk.ca

Suggested citation:

MILLIGAN, H.E. 2015. Invasive species survey: Didymo algae 2014. Yukon Fish and Wildlife Branch Report SR-15-01. Whitehorse, Yukon, Canada.

Summary Didymo algae (Didymosphenia geminata) is a freshwater that can form massive blooms with the potential to impact fisheries. Many jurisdictions consider didymo to be a non-native invasive species and have banned felt-soled wading boots to restrict the spread of the organism. New evidence suggests that it is native to southern Canada and that recent blooms may be due to the emergence of a new genotype or changing environmental conditions. Although didymo is known to occur in Yukon, it is not clear if the species is native to Yukon, how widely it is distributed, or whether this distribution is changing. To begin to answer these questions, Environment Yukon began recording observations of didymo in 2010 from opportunistic sampling and public submissions. This report summarizes the findings on the distribution of didymo algae.

Key Findings • Didymo algae is well established and occurs in all major watersheds in Yukon that we sampled (Yukon River, Alsek, Peel, and Liard drainages). • Most observations of didymo blooms occurred in southern Yukon in the Yukon River and Alsek drainages.

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Didymo Survey 2014 iii Table of Contents Acknowledgements ...... inside cover Summary ...... ii Key Findings ...... ii Table of Contents ...... iv List of Figures ...... iv Introduction ...... 1 Methods ...... 1 Results and Discussion ...... 2 Conclusions and Recommendations ...... 5 References ...... 6

List of Figures Figure 1. Locations of Didymosphenia geminata in Yukon from 1992-2014 records (n = 88 sites). Blooms are sites with mats of didymo coverings rocks. Sites without mats of didymo that had didymo identified in algal samples, are identified as “present”...... 3 Figure 2. Didymo mat covering rock at Porter Creek...... 4 Figure 3. Didymosphenia geminata cell and attached extracellular stalk from Aishihik River. Magnification 400x...... 4

Didymo Survey 2014 iv to induce algae blooms. Didymo may respond to low levels of phosphorus Introduction by increasing extracellular stalk Didymo algae (Didymosphenia production thus extending cells into geminata) is a freshwater diatom the water column where they can that can form massive blooms with more easily uptake phosphorus the potential to impact fish habitat (Taylor and Bothwell 2014). and fisheries. When individual cells Environment Yukon conducted form extracellular stalks, the an assessment of aquatic invasive organisms can group together in a species to develop a framework for continuous mat that covers stream aquatic invasive species bottoms (Taylor and Bothwell 2014). management and to better This didymo mat, also known as understand which species posed the rock snot, is extremely slippery and highest risk to Yukon waters. gives the impression of polluted Didymo, which is known to be waters, thereby reducing the present in Yukon waters, was the aesthetic qualities of pristine waters. highest ranked species based on the In recent years, numerous likelihood of introduction, observations of these mats in new persistence, and ecological, areas generated global concern economic and social consequences about the impact and spread of (Environment Yukon, In Prep). didymo. Notwithstanding this Many jurisdictions consider assessment, it is not clear if didymo didymo to be a non-native invasive is native to Yukon, how widely it is species. Didymo blooms are thought distributed in Yukon, or whether to be caused by recent introductions this distribution is changing. To by people using streams. Several begin to answer these questions, jurisdictions (, , Environment Yukon began , Nebraska, Rhode Island, surveying streams for didymo in , , Chile, and 2010. In 2014, we extended this New Zealand) have passed survey for didymo to better legislation banning the use of felt- understand its distribution in soled wading boots to restrict the Yukon and to collect genetic spread of the organism. samples for further analysis on the New evidence suggests that origin of this species. didymo is native to some areas in southern Canada and that recent blooms may be due to the Methods emergence of a new genotype that Road accessible sites were surveyed produces the mat-forming in southern Yukon by a field crew. extracellular stalks or to changing We primarily visited streams with environmental conditions (Taylor rocky bottoms near highway and Bothwell 2014). In particular, crossings. Several samples came low levels of phosphorus in the from opportunistic collections at environment has been hypothesized non-road accessible sites and from

Didymo Survey 2014 1 submissions by members of the Results and Discussion public. At each sample site, when time We found didymo at 30 locations, permitted, we recorded several indicating that the species is well habitat variables including established in Yukon (Figure 1). accessibility, stream width, current Didymo occurred in all of Yukon’s speed, stream depth, pH, specific major watersheds that we sampled: conductivity, water temperature, Yukon River, Alsek, Peel, and Liard shade cover, and presence of drainages. Most observations of didymo mats. We preserved a didymo blooms were from southern sample of the didymo or any other Yukon—in the Yukon River and algae found at the site in 70% Alsek drainages. The earliest ethanol for identification and genetic documented cases of didymo in sampling. We then disinfected Yukon were from 1992 when didymo footwear and equipment in diluted mats were found in the Yukon River bleach. near Whitehorse and in the Didymo presence was confirmed Thirtymile section downstream from by compound microscopy using Lake Laberge (Barraclough 1992). modified protocols from Kilroy We confirmed that didymo occurs (2007). Didymo observations were at 38% of the stream locations entered into a database that sampled in Yukon (bloom = 22, recorded opportunistic sampling, present = 8, unconfirmed = 1, total public submissions, and records surveyed sites = 88). Didymo from reports. The status of didymo appeared to be located primarily in was determined and classified as: medium flow streams with rocky not detected, present, bloom, or substrates in both easily accessible unconfirmed. Blooms were sites and inaccessible areas (Figure 2). with mats of didymo covering rocks. Extracellular stalks were primarily Sites without didymo mats that had associated with samples with didymo identified in algal samples noticeable didymo blooms (Figure 3). were defined as present. We also We collected 9 genetic samples recorded public submissions that for further analysis on the origin of were not confirmed by microscopic the species. analysis. The database, which includes observations from 1992 to 2014, is not presented here, but can be accessed by contacting Environment Yukon.

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Figure 1. Locations of Didymosphenia geminata in Yukon from 1992-2014 records (n = 88 sites). Blooms are sites with mats of didymo coverings rocks. Sites without mats of didymo that had didymo identified in algal samples, are identified as “present”.

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Figure 2. Didymo mat covering rock at Porter Creek.

Figure 3. Didymosphenia geminata cell and attached extracellular stalk from Aishihik River. Magnification 400x.

Didymo Survey 2014 4 us understand the environmental factors that may be causing the Conclusions and species to form mats. Recommendations Regular monitoring of didymo in We found that didymo was more Yukon should consider engaging widespread than anticipated and non-governmental organizations and was detected in all Yukon the public. This would have many watersheds that we sampled (Alsek, benefits, including providing Liard, Peel, and Yukon River). This information on the stability (or survey provides a baseline for spread) of didymo distribution in presence and absence of didymo in Yukon. some Yukon rivers. It does not show Carrying out studies to whether didymo is spreading or understand the impact of didymo on answer the question about how long aquatic environments will allow us it has been in Yukon and whether it to quantify risk posed by didymo in affects the aquatic environment. Yukon. Further research will improve our Finally, a continued focus on understanding of didymo presence public education about invasive in Yukon. Based on our current species, particularly on those good knowledge, we have the following practices that will help to prevent recommendations. the introduction and spread of We recommend that an analysis aquatic organisms. Even if didymo of the genetic fingerprint of specific is found to be native to parts of didymo samples be carried out to Yukon, we know from this survey compare Yukon samples with that it is not currently found samples from other parts of North everywhere in the territory. Keeping America. This will help us didymo and all other aquatic species understand where didymo in Yukon to those areas where they already came from and whether it is native exist will help maintain the quality, to Yukon. Understanding whether diversity, and integrity of Yukon’s didymo in Yukon is similar to aquatic environments. didymo in other areas may also help

Didymo Survey 2014 5 References BARRACLOUGH, C.L. 1992. Periphyton of the Yukon River presence of Didymosphenia geminata (Lyngb.) M. Schm. University of Victoria report. Victoria, B.C. ENVIRONMENT YUKON. In Prep. Development of a framework for management of aquatic invasive species of concern for Yukon: Literature review, risk assessment and recommendations. Yukon Fish and Wildlife Branch Report MR- 14-01, Whitehorse, Yukon, Canada. KILROY, C. 2007. Protocol for microscopic analysis of samples for the detection of Didymosphenia geminata. National Institute of Water and Atmospheric Research Ltd., Christchurch, New Zealand. TAYLOR, B. W. and M. BOTHWELL. 2014. The origin of invasive microorganisms matters for science, policy, and management: the case of Didymosphenia gemimata. BioScience 64:531- 538.

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