Tiny bubbles saving Lake Tahoe from invasive weeds
More bubble curtains planned in 2021 to restrict spread of destructive plants
Lake Tahoe is known as the “Jewel of the Sierra,” but one of the biggest threats to that infamous title are aquatic invasive plants, which have run rampant in some parts of the lake.
Not only do these unrelenting weeds threaten the lake’s unmistakable beauty, but they also pose a threat to the native ecology and water quality. Over the years, there have been several methods deployed by local agencies and nonprofits to combat this issue.
In 2018, Lake Tahoe became home to cutting-edge technology with a mission to control aquatic invasive plants.
A “bubble curtain” was placed on the west channel of the Tahoe Keys on the South Shore to restrict destructive, invasive plants from escaping into the lake. Based on visual success from the first curtain, The League to Save Lake Tahoe together with partners, including the Tahoe Keys Property Owners Association, plans to add another on the east channel by teaming with Tahoe Regional Planning Agency and Elk Point HOA, where another one is planned for the Elk Point Marina.
While new to Tahoe, bubble curtains have been used for decades internationally before reaching the Sierra.
Originally used for aquaculture and removing floating debris in the Northwest, applying the technology of the curtain to protect the lake from spreading aquatic invasive species is a pioneering tactic.
The “V” shaped curtain helps contain invasive plants to the Tahoe Keys and prevents them from spreading by boats and water currents.
The bubbles help dislodge floating plant fragments from boats as they leave the lagoon and pass through a fine wall of floating bubbles shooting from a hose that lays on the bottom powered by a compressor.
Fragments then get pushed to the sides to be removed by either a collecting device like a sea bin or even hand removed with a pool skimmer.
Chief Strategy Officer for The League, Jesse Patterson, said these curtains help reduce the spread as they tackle the 172 acre infestation at the Keys.
“If we want to address aquatic invasive species, we have to go to the source,” Patterson said.
TRPA’s Aquatic Resources Program Manager Dennis Zabaglo is also partnering with The League to place a “double bubble” curtain — which is an additional curtain of bubbles — on the east channel along with a curtain at Elk Point Marina on the Nevada side of the lake.
However, the curtain will be placed a bit differently at Elk Point.
Funded partially by the Lake Tahoe Restoration Act, the “V” will be inverted to keep fragments from reinfesting the marina.
Due to a prior infestation, the marina has already been treated in the past and the curtain would be used to keep fragments at bay and protect it from further infestation.
“We will see if the technology works in reverse,” Patterson said.
Both Patterson and Zabaglo have an excited and optimistic outlook on the projects.
“It might even be more effective and the amount [of fragments] is less than what is trying to escape the Keys,” Zabaglo said. “We are really excited. It is really rewarding to see we are utilizing innovation to solve difficult problems.”
He said they are always trying new methods and tools to find solutions.
According to Patterson, plant fragments are most prevalent from late July through September. Both curtains in the east channel and at Elk Point are planned to be installed in April or May.
The curtains are relatively low in cost in comparison to other methods. Each curtain is $20,000-30,000 and there is also annual maintenance and electricity.
Curtains have previously been used to collect larger fragments, but Patterson said some of the plant fragments can be as small as a thumbnail.
The curtain also does not pose any hazards for fish or birds as they can easily swim through.
With a bit of tweaking and modifications through the learning process, which included conferences in Canada, Patterson said that 2020 ended up being the most successful year with this new method.
For the bubble curtain at the west channel of the Keys, the TKPOA provided the funding, maintenance, monitoring and electricity needed to keep the curtain running and will do so for the east channel as well.
The east channel is larger and includes the marina, condominiums, concessions and boat slips while the west is primarily property owners.
Since August, the compressors have been running nonstop, ensuring invasive plants could not escape.
Patterson said the TKPOA is continuously monitoring the curtain and has removed tons of fragments since its installation from both the curlyleaf pondweed and Eurasian watermifoil, which are the two primarily aquatic invasive plants that cause the most concern.
A new report set to be released in about a month should have the amount of fragments collected in the bubble curtain. But it won’t say if any, or how many, fragments got through the curtain due to the inability to determine if they were inside the Keys or already on the outside of the curtain.
About 90% of the Tahoe Keys are filled with these invasive weeds. If let alone they could grow so thick a person could almost walk on top of them.
At the Keys, weed harvesting happens every year so boats can pass through, however, when these weeds are “harvested” it breaks them to smaller fragments that make spreading easier which are now being caught by the curtain.
Recently, the Tahoe Keys Complex — similar to how wildfires are characterized when multiple break out in one area — was mapped and showed infestation spanning 105 acres into the lake, which is by far the largest infestation in Lake Tahoe.
“This is massive,” Patterson said.
Last Fall, The League initiated a suction dredging cleanup that it had been advocating for since 2016. The League raised private money and, along with funds from the Lake Tahoe Restoration Act, The Tahoe Resource Conservation District contracted a firm called Marine Taxonomic Services to do the dive suction work on 3 acres in one the most dense areas of the Tahoe Keys Complex right outside the Keys channel.
While expensive — it costs roughly $50,000 per acre — the results were effective.
“It worked really well,” Patterson said.
The group is now gearing up on another year of tackling the Tahoe Keys Complex.
“I would argue that this [aquatic invasive plants] is the biggest threat to Lake Tahoe,” he said.
The League also plans to add another curtain to the already existing one on the west channel of the Tahoe Keys with hopes that the double bubble curtain will be twice as effective.
“We can drill down and monitor its effectiveness and actually see the percentage of how much it is collecting,” Patterson said.
To help fund and initiate the projects, public and private partnerships with The League have included the TRPA, TRCD, TKPOA, Elk Point HOA and Tahoe Fund.
Said Patterson, “It is good to see money going to on-the-ground projects that are making a difference.”
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