In 2012, the National Park Service found a few quagga mussels growing in Lake Powell, a vast reservoir on the Colorado River in Arizona and Utah. They had been there for years.
After two years of intense eradication, education and monitoring efforts, park managers were forced to give up because the mussels were already too established. Instead they had to focus on keeping the mussels from moving to other areas.
This defeat is a good example of the importance of early detection, showing how quickly an irreversible introduction of invasive species can happen.
Aquatic invasive species are not new to Montana waters, but some of the most damaging to aquatic ecosystems, such as quagga and zebra mussels, have not yet been found in the state. They continue to arrive, however, at boat check stations, carried by unsuspecting boaters coming from infested waterways.
Scientists hope that a new technology will help protect these waters by providing early detection and monitoring without having to spot invaders visually.
In fact, all that is needed is one biological cell.
Environmental DNA or eDNA is a way of collecting genetic material without having to find or capture a rare or hard-to-find species. Scientists are now using DNA tests that capture water samples and in the lab look for unique markers to each species.
DNA contains the genetic instructions to make a living thing. Each species of organism has a unique set of genes, and each cell from that organism carries a complete set of those genes. When a plant or animal sheds some of those cells — from a fish’s scale, a leaf or plant tendril, or from blood, sperm, urine or pollen — it enters the environment.
To find out how scientists are chasing down DNA, I spent a summer afternoon at Glacier National Park. Snow-capped Stanton Mountain waits in a raincloud at the opposite end of Lake McDonald as I stand and watch eDNA sampling.
Standing at the shore, Gordon Luikart watches the mountains to track if rain or lightning will interrupt his experiment. He is a conservation geneticist at the Flathead Lake Biological Station, a part of the University of Montana. A transplant from Iowa, he traces his first interests in biology and conservation to his love of fishing and being outdoors.
Today he is speaking to his summer class of conservation biology students while holding a fine-meshed net called a plankton net, usually used to collect small aquatic creatures.
“You can detect a single cell of anything that’s touched the water, defecated from above or swam through the water,” Luikart said.
A bright flash of lightning strikes at the other end of the lake and a brief echo of thunder rolls across the lake. “Whoa, lightning. Who wants to hold the net?” Luikart asks jokingly. No one takes it.
On the floating dock, Steve Amish, a genetic researcher at the University of Montana, drags a long, fine mesh net through the water along the dock to capture drifting detritus.
On the first try the net catches mostly cottonwood tree fluff, but on a second pass in deeper water the sample shows up cleaner. Amish raises the net up in the air to drain most of the water. Jenna Schabacker, a young, soft-spoken researcher, who works with eDNA in his lab, rinses the remaining debris with ethanol into small vials.
The samples they collect don’t look like much, with tiny bits of material sometimes visible in the bottom, but in each of the samples hide the signatures of potentially every species that has touched the lake.
Suddenly the students shout in excitement as they look into the vial. A small pair of eyes peer out. It’s a fish larva.
“We will probably detect that one with an eDNA test. But what species is it?” Luikart says, “You can’t tell without a DNA test.”
Amish and Schabacker take these samples back to the Montana Conservation Genetics Lab in Missoula, where they work.
THEY WILL LOOK FOR DNA from invasive species that aren’t supposed to be in the lake as well as others they already know are there, such as non-native lake and rainbow trout, as proof of principle. Their real enemies are the animals and plants they hope they’ll never find: zebra and quagga mussels. They will also look for the mussels with eDNA in the environment.
To do this, Luikart and his team have to improve the methods of sampling waterborne genetic material. Using eDNA on a large scale in the open environment remains largely unproven. In the Flathead, one of the gems of Montana, no one else has undertaken such a task.
To that end, the lab will start testing with a small unmanned submarine that will take water quality and eDNA samples and process them in real time inside the vehicle and beam the results back to shore. Luikart also received funding to start design on another sampler that will sit in place at heavily used sites to take samples over time to monitor for invasive species.
“Flathead Lake is by far the most likely location of invasion,” says Luikart, who wants to see the prevention and monitoring work done by the state and other agencies to be enhanced by these new quick detection tools.
Boat check stations dot the major entryways into Montana’s lakes and streams. There are gaps in coverage, though.
Environmental DNA might be the tool that can overcome these limitations.
SCIENTISTS HAVE USED eDNA successfully to detect rare species such as salamanders in Idaho and fish populations, such as the chinook salmon in Washington, at a fraction of the cost of traditional field sampling methods that require capturing multiple individuals.
However, one drawback is that you can’t pinpoint the exact location of the species since the eDNA it shed is constantly drifting in the water.
There is a potential for false positives with eDNA, as in detection of Asian carp in the Great Lakes in 2010 that caused a brief panic when the carp weren’t known to be there.
Luikart is frank about eDNA’s uphill climb as an environmental sleuth.
“We developed our own test from DNA sequences on zebra and quagga [mussels] and just started applying it,” Luikart said. “So far the test is sensitive enough to detect invasive species in controlled environments. Outside the laboratory, there are many barriers that make accurate tests much more difficult.’’
DNA can move in many ways and find its way into places where it isn’t expected to be.
People move plants and animals around all the time. Most don’t pose a great danger. But some invasive species have a real potential to change the places we think of as pristine.
One of those is the mussel.
“Zebra [and quagga] mussels will take food away from other organisms like young fish and they will also excrete nutrients and will likely cause fisheries to collapse,” says Luikart. After introduction, the high concentration of nutrients at the surface of water and at the shorelines can lead to algal blooms that feed on nutrients and cause die-offs of fish.
Each female mussel has the ability to produce up to a million offspring in a lifetime of several years. The tiny larvae are no larger than a fingernail. No place is safe as mussels slowly creep their way to new waterways in the bilge of a boat or by clinging to a hull.
Every year boats from the Southwest and Great Lakes with mussels attached to them come through Montana boat check stations.
Currently, the only way they will be stopped is if someone actually sees them. State employees and other agencies collect water samples and send them to the Montana Fish Wildlife and Parks Aquatic Invasive Species Lab in Helena. At the lab, workers visually examine the samples for evidence of invasive mussels, plants, and snails under a microscope.
DNA tests are used only to verify visual findings.
“We certainly see a possibility for implementing eDNA, but for now the money’s better spent elsewhere,” says Stacy Schmidt, the manager of the Aquatic Invasive Species Lab. “We do support the research being done.”
So far, the lab hasn’t found a mussel in a Montana lake or river, except for those found on trailered boats.
Luikart argues that it’s too easy to miss an invasive species using just visual inspections.
You need a large piece of an adult or a larva to see under a microscope. With eDNA, a single cell or even a molecule could be picked up in extracted DNA.
With his collaborators, Luikart would like to start regular eDNA monitoring on Flathead Lake. The Flathead Lake Biological Station estimates that monitoring would cost $40,000 a year with testing done multiple times every summer in strategic points around high-risk areas such as boat launches and marinas.
Luikart quotes his colleague, Adam Sepulveda with the U.S. Geological Survey in Bozeman, who has been working to set up a similar eDNA invasive species detection system around Yellowstone National Park:
“If you detect a cancer early,” in this case an invasive species, “like an invasion or tumor, you can excise it early from the body or ecosystem.”
eDNA can help to do just that.
Part 1 on invasive species already in Montana can be found here.
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This story was originally puplished in the Daily Inter Lake in Kalispell, Montana and Solutions Journal as a part of the Crown Reporting Fellowship at the University of Montana School of Journalism with the guidance of mentor Christopher Joyce at National Public Radio to generate environmental stories about the Crown of the Continent.