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Recently discovered invasive threatens to choke Peninsula lakes

  • Author: Joseph Robertia
  • Updated: May 12, 2016
  • Published February 17, 2013

SOLDOTNA -- Hearing about invasive terrestrial plants is unfortunately getting to be routine on the central Kenai Peninsula as residents are asked year after year to do their part to prevent invasives such as dandelions, bird vetch and purple loosestrife from spreading across the land.

Now a newly discovered invader -- the first submerged aquatic -- has upped the alarm in necessity of response as it's one that can cause so much damage so quickly that biologists are asking for everyone's help to immediately start combating its spread.

"This is a really bad one. This is the one we were worried about because it could hurt the fisheries of the entire peninsula. It's a really big deal," said John Morton, supervisory wildlife biologist with the Kenai National Wildlife Refuge.

The aquatic invader is known as "elodea" and has recently been discovered in Stormy and Daniels lakes in Nikiski as well as some slow-moving waters in other parts of the state including Anchorage, Fairbanks and Cordova.

"We're concerned because not only was this stuff unheard of up here five years ago but also because this stuff is spread so easily," Morton said. "It reproduces asexually, so only a tiny little piece of it on a boot, fishing gear, a boat prop, a float plane -- and it can take off again in a new waterbody."

Added to its ability to spread from a tiny piece, the plant also thrives in cool water conditions and even continues to grow under the ice in winter. In the Lower 48 and in Europe, elodea outbreaks have gotten so thick that the growth has to be mechanically mowed with specialized equipment or removed by backhoe as part of the eradication process.

"It grows so abundantly that it literally shuts down the ability to run a boat motor through it. It'll foul floatplane rudders and boat props. It'll foul launch sites and shore habitats, and it degrades salmon spawning habitat," said Libby Bella, a refuge ecologist.

"So it's not just ecological damage but economic damage that can happen from it radically changing habitat," Bella added.


It's unclear how elodea came to be present in Central Peninsula lakes. Bella said that, for several years, the plant was a staple part of science kits sold to biology classes around the state. It was also sold regularly at pet stores as a common aquarium plant.

"It's tough to say for certain," Morton said. "But this could have begun from something as simple as a kid dumping his goldfish in a lake."

Morton said that while it is unfortunate elodea was found on the Kenai Peninsula at all, how it was found was quite serendipitous since biologists stumbled on it while focusing on an entirely different invasive species.

"It was incidentally found in September of 2012 while Stormy Lake was being treated with rotenone to eradicate northern pike," Morton said. "Prior to that, invasive freshwater plants weren't known to occur on the Kenai Peninsula."

Realizing there was a new threat in the lake, biologists from multiple agencies sprung into action to try to determine how widespread the threat might be including the Kenai National Wildlife Refuge, Alaska Department of Fish and Game, Department of Natural Resources, U.S. Fish and Wildlife Service, University of Alaska Fairbanks Cooperative Extension Service, Cook Inlet Aquaculture Association, Homer Soil and Water Conservation District, Kenai Watershed Forum and the Kenai Peninsula Cooperative Weed Management Area.

Fish and Game surveyed the distribution of elodea in Stormy Lake by sampling with a "rake" made from a modified chimney brush that when submerged collects elodea.

From the 150 rake throws conducted from around the entire circumference of the lake, elodea was determined to be present in roughly 20 percent of the throws and mostly at depths of 7 to 9 feet, Morton said.

In October, Fish and Game, joined by employees of the U.S. Fish and Wildlife Service Kenai Fisheries Office, conducted a less formal survey of nine other lakes: Salamatof, Longmere, Island, Sport, Scout, West Mackey, East Mackey, Wik and Daniels.

"A single strand of elodea was detected in Daniels Lake at that time," Morton said.

To determine how widespread elodea was at this locale, the staff from multiple agencies this month took to Daniels Lake to collect samples, the first through-the-ice sampling for invasive aquatics conducted in Alaska.

They auguered through the ice at 25 sites -- three holes per site -- distributed systematically around the 10-mile perimeter.

"Elodea was detected at two sites adjacent to each other on the southern shore," Morton said.

More startling than its presence was how well it was doing under the thick ice.

"When we augered the hole and water splashed out, the elodea splashed out with it, vibrant and green. There was essentially no dieback in winter," he said.

Despite that, elodea has only been detected in two local lakes, one of which is in the refuge.

Morton said that knowing how quickly and easily it could spread and choke out other bodies of water around the Kenai Peninsula is what has biologists from multiple agencies scrambling to take action against the aquatic intruder.

"What's driving us is we're running out of time to do something proactive. We need to do something this summer because the stakes are so high. Each summer that goes by that we don't treat it, we risk it being spread, which will just make it more difficult and expensive to treat when we do finally commit to eradication," Morton said.

There are multiple approaches that could be taken to eradication depending on the size of the outbreak. Elodea in other areas has been treated with underwater vacuums and herbicides but the latter of these can get expensive.

Depending on the chemicals used, herbicides can cost as much as $750 per surface acre, and there are roughly 1,000 surface acres between Stormy and Daniels lakes, Morton said.

Adding to the situation, while Stormy Lake is located on the refuge, Daniels Lake is not, and has roughly 136 private landowners who will all need to be informed of the situation and be allowed to give input into any planned elodea-eradication process.

"We want stakeholder participation. We want people to know how bad this could be so that eradication can be done," Morton said.


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