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Refuge Notebook: A window of opportunity to eradicate Elodea

Posted: November 7, 2013 - 4:24pm
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Photo courtesy Kenai National Wildlife Refuge Native aquatic plants accidentally caught on the float rudder of a Piper Super Cub show how Elodea could be carried from one watershed to another.
Photo courtesy Kenai National Wildlife Refuge Native aquatic plants accidentally caught on the float rudder of a Piper Super Cub show how Elodea could be carried from one watershed to another.

Mark Twain was supposedly fond of saying “I was seldom able to see an opportunity until it had ceased to be one.” I don’t claim to be prescient most of the time, but when it comes to ridding the Kenai Peninsula of Elodea, the first submerged freshwater invasive plant to make it to Alaska, I’m pretty confident that we have only a very small window of opportunity.

About this time last year, Elodea had been discovered for the first time on the Kenai Peninsula in Stormy Lake (400 acres), with a single fragment found on the shores of Daniels Lake (620 acres). In February, we returned to Daniels Lake to confirm that Elodea was growing there with an ice auger and a modified chimney sweep as our sampling device. We returned by boat in late May just after ice-out to better assess its distribution in the lake.

At that point, we were hoping to begin using herbicide in these lakes with the goal of eradicating Elodea from the Kenai Peninsula. However, based on the bathymetry of the lakes and the distribution of Elodea, the estimated cost of eradication was higher than anticipated — $400,000 for Fluridone, the best chemical on the market for killing Elodea. That’s a big sticker price but well worth the effort and cost if we successfully eradicated Elodea from the peninsula. Keep in mind that elsewhere in North America, Elodea has grown so thick that boat traffic is hindered and dissolved oxygen is reduced to the point that fisheries populations are impaired. But what was making us uncomfortable was that lurking question of whether or not Elodea occurred in more lakes than just those two on the peninsula.

So, with grants from the U.S. Fish and Wildlife Service and the Kenai Peninsula Fish Habitat Partnership, Cheryl Anderson from the Kenai Fish & Wildlife Field Office and Elizabeth Bella from the Kenai National Wildlife Refuge launched surveys of lakes this summer to help us answer this question. With agency staff and volunteers from the Friends of Alaska Refuges, 64 lakes were surveyed on the western Kenai Peninsula, from Tern Lake in the east to Johnson Lake in the south to Vogel Lake in the north. We targeted lakes exposed to likely routes of “infection”: public boat launches, multiple private homes, road accessible, or floatplane charters. We surveyed intensively in the area north of Nikiski including a day-long paddle down Bishop Creek.

Along the way, we collected water quality data from most of the lakes as well as data on the distribution of our native aquatic plant community. Thirty-four species were identified, of which 14 were pondweeds of the genus Potamogeton, including P. robbinsii, a species considered rare in Alaska. The good news is that despite this extensive effort over multiple watersheds, Elodea was found in only one additional lake in the Bishop Creek watershed, the 200-acre Beck Lake. A salient point is that we also failed to detect any other nonnative submerged aquatic plants. All evidence suggests that Elodea is constrained to the Bishop Creek and Swanson River watersheds. From the perspective of the salt-intolerant Elodea, however, Stormy Lake is functionally its own watershed as the outlet passes through the tidal portion of the Swanson River.

I was pleasantly surprised to find that Bishop Creek is a wonderfully diverse system with a much richer and more abundant aquatic plant community than I had previously believed. The bad news is that if Elodea ever gets established in Bishop Creek, I doubt we’ll be able to get rid of it. And the problem with allowing a source of Elodea to remain on the Kenai Peninsula is that Elodea can be spread so easily. A single fragment can infect a water body as it reproduces asexually.

In the case of our current three-lake infestation, the plausible scenario is that an aquarium was dumped with Elodea, probably in Beck Lake, and it has since spread. Analyzing DNA, Dr. Don Les at the University of Connecticut has identified Elodea samples from Daniels and Stormy Lakes as a hybrid, which is often the case with commercially-grown populations. If the Elodea from Beck Lake proves to be a hybrid as well, it will lend support to the notion that Elodea in all three lakes originated from a single source.

With a clear picture of where Elodea occurs, partners in the Kenai Peninsula Cooperative Weed Management Area are working on a detailed plan for eradicating Elodea from the three lakes over the next two or three years. Contingent on funding, which is admittedly prohibitive, we are committed to applying the first Fluridone treatments this spring shortly after ice-out.

We will work with private landowners on Beck and Daniels Lake to help contain Elodea to its current distribution. We also ask local pet shops and science teachers to be very aware of what they sell and purchase. This is certainly the best and probably the only opportunity we’ll have to rid the peninsula of Elodea given the high treatment costs and harsh reality of trying to contain Elodea once it spreads to remote lakes.

John Morton is the supervisory biologist at Kenai National Wildlife Refuge. You can find more information about the refuge at http://kenai.fws.gov or http://www.facebook.com/kenainationalwildliferefuge.

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