From Lakes to Labs: Tracking Zebra Mussels with eDNA
When zebra mussels were first discovered in Lake Témiscouata, Québec, in the fall of 2022, the New Brunswick Invasive Species Council quickly mobilized to collaborate with partner organizations throughout the Wolastoq (Saint John River) watershed. With support from the Aquatic Invasive Species Prevention Fund, we launched eDNA monitoring and collector plate deployment efforts across the watershed. Since then, we've received many questions about our monitoring plans and methods, prompting us to provide a comprehensive overview of our approach and current findings.
What is eDNA?
Living organisms constantly release DNA into their surroundings through shedding hair, skin, gametes, or excrement. As a species moves through an environment, it leaves behind this genetic material, which can be used to identify it. This genetic material, known as environmental DNA or eDNA, refers to the DNA left behind by organisms in their environment.
All species have DNA, which is made up of the same components, just in different orders, called sequences. Scientists identify unique sequences of DNA for each species called a “barcode”. Researchers can then take samples from an environment and compare the eDNA they gathered against known DNA barcodes to identify the species in their sample.
This monitoring method especially useful for species that can be hard to identify with other means, such as species that are very small, have few individuals, or that move through the environment quickly. The procedure for collecting the sample is non-invasive, meaning you don't have to interact with the species, making it less disruptive. eDNA sampling can be used with soil, air, or water samples; it works particularly well in water, where the genetic material is suspended in the water column.
How do we collect eDNA samples?
To collect an eDNA sample, our team uses a specialized filtering machine to filter a 1.5 liter sample of water from a lake or river. The water passes through a filter, which collects biological material found the in the water (the shed hair, skin, gametes, or excrement mentioned above). The filter is then sent to a lab, where the eDNA is extracted and compared to known species DNA barcodes to identify the species in the sample.
How do we choose our sampling sites?
For the 2024 monitoring period, we are focusing on the Wolastoq watershed and surrounding areas. This is because we know that there is a constant source of introduction from the top of the river (Lac Témiscouata, Québec), so it is likely to spread downstream. We're monitoring high-risk waterbodies, such as those with heavy boat traffic, and focusing on areas with suitable habitat conditions, like appropriate calcium levels and salinity, where zebra mussels are more likely to thrive.
What are the current eDNA results for zebra mussel detection and what do they mean?
A negative result is typically conclusive to say they are not present in the area. A positive result is an indication that they are nearby, but we do not use that as conclusive evidence that they are present in a waterbody. This is because eDNA can last in the water column for several days and there is a possibility that it could have been carried to the sampling location by wildlife or human activities. For example, the eDNA could have been moved from where it originated by the movement of water downstream or it could have been carried by a duck that ate zebra mussels elsewhere and excreted them in the sampling location. Positive detections let us know where we should follow up with more conclusive dectection methods like visual surveys, veliger sampling, or collector plates.
Currently, there have been positive zebra mussel eDNA detections from Edmundston to the Mactaquac Dam. At present, the only confirmed observation of adult mussels in New Brunswick has been on the Edmundston hydroelectric dam. This means that we know that they are in the Madawaska River, and is an indication but no confirmation that they have spread down the Wolastoq/Saint John River.
This year, we are working closely with government agencies, municipalities, non-profit organizations, and local aquatic businesses to conduct eDNA testing, veliger sampling, and installing collector plates all throughout the Wolastoq watershed, as well as some nearby and high-risk waterbodies to follow up on the current eDNA results.
What can I do?
When you’re on or near a river or lake, check any hard surfaces that sit in the water (like boats, docks, and rocks) for the presence of attached adult zebra mussels. If you think that you have found a zebra mussel, it is important to report the sighting to the Fisheries and Oceans Canada (DFO) or the New Brunswick Invasive Species Council using the information below. Reporting early sightings will help us to combat their spread to other waterbodies.
Fisheries and Oceans Canada
Phone: 1-866-759-6600
Email: DFO.GulfAquaticInvaders-EnvahisseursaquatiquesduGolfe.MPO@dfo-mpo.gc.ca
New Brunswick Invasive Species Council
Phone: (506) 452-6907
Email: report@nbinvasives.ca
It is also important to Clean, Drain, and Dry all aquatic recreational equipment before and after entering a new waterbody. Examples of equipment include boats and internal compartments, canoes, kayaks, paddleboards, floaties, lifejackets, and fishing equipment.