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Aquatic invasion: Asexual weed reproducing like crazy in Kenai Peninsula lakes

Joseph RobertiaRedoubt Reporter
The invasive aquatic plant Elodea may be gaining a foothold in Alaska lakes. Kristian Peters photo

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 set off alarms. It can cause so much damage so quickly that a small army of biologists are soliciting help to combat 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.

Tiny asexual plant reproduces like crazy

“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 water body.”

Added to its ability to spread from a tiny piece, the plant also thrives in cool water conditions -- and continues to grow under the ice come 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 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.

Multiple agencies respond 

“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, how it was found was quite serendipitous. 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 and determine how widespread the threat might be. Alaska Department of Fish and Game biologists surveyed the distribution of elodea in Stormy Lake by sampling with a “rake” made from a modified chimney brush that, when submerged, collects elodea if present.

From the 150 rake throws conducted around the circumference of the lake, elodea was determined to be present in roughly 20 percent of them, 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.

Through-the-ice sampling

To determine how widespread elodea was at this locale, staffers from multiple agencies took to Daniels Lake last week 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.

'Running out of time'

“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, depending on the size of the outbreak. Elodea in other areas has been treated with underwater vacuums and herbicides, but the latter can get expensive. Depending on the chemicals used, herbicides can cost as much as $750 per surface acre, and there are roughly 10,000 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. Its roughly 136 private landowners will all need to be informed of the situation and offered the chance to give input about 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.

To begin informing the public about ways to minimize the spread of elodea, and to gather information on the community’s desire for how best to battle the aquatic invasive, a public meeting will be held at 6 p.m. Tuesday, Feb. 19, at the Nikiski Community Recreation Center.

Joseph Robertia is a reporter for the Redoubt Reporter, which covers the Kenai Peninsula. Used with permission.