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Putting aquatic invasive weeds in check

The Tahoe Keys are ground zero for the infestation of invasive weeds at Tahoe.

The situation in the Keys
Aquatic weeds, unintentionally introduced by humans, have taken over more than 90% of the 172 acres of lagoons in the Tahoe Keys, a development on Tahoe's south shore. During the summer, the Keys' waters are a weed-choked, murky green.
A threat to the entire Lake
Left unchecked, aquatic invasive weeds threaten to destroy Lake Tahoe’s native ecology, water quality and world-famous clarity. These problem plants are growing out of control in the Keys and spreading into the Lake itself.
The League's involvement
Since 2013, the League has been deeply involved in addressing the infestation of aquatic invasive weeds in the Tahoe Keys – ground zero for the problem at Tahoe. With a consistent, credible voice and the best available science, the League has collaborated, innovated and funded cutting-edge treatments to tackle invasive species. Our leadership has been pivotal in designing and implementing the Tahoe Keys Control Methods Test, a program to find a safe, long-term solution to the problem in the Keys and protect water quality lakewide.

Watch SCUBA divers at work.

See how a bubble curtain controls invasive weeds.

REMOVAL: Tackling the Tahoe Keys Complex

Crews are working to remove aquatic invasive weeds from a 100+ acre infestation known as the Tahoe Keys Complex which is growing immediately outside of the Keys in Lake Tahoe proper. The League flagged the growing infestation as a concern and kickstarted the removal process by providing funding. Watch the video above to catch a glimpse of the SCUBA diver-assisted suction dredging.

Explore interactive panoramas of the Tahoe Keys Complex before and after initial treatment. (Images courtesy of Sierra Overhead Analytics.)

The aquatic invasive weed removal work is being performed by Marine Taxonomic Services, with funding and coordination from the League to Save Lake Tahoe, Tahoe Regional Planning Agency, California Tahoe Conservancy, Tahoe Resource Conservation District and Tahoe Keys Property Owners Association.

CONTAINMENT: Following nature’s lead

In 2018, innovative technology was installed in one of the Keys’ boating channels to prevent invasive weeds from being transported into the Lake by passing boats and water currents. The bubble curtain emits a wall of tiny bubbles – mimicking the fishing techniques of humpback whales – to dislodge floating weed fragments and corral them for removal.

After the success of the 2018 pilot project, bubble curtains were installed in the Keys west channel, as well as Elk Point marina. Marine Taxonomic Services installed the bubble curtains with funding and coordination from the League, Tahoe Regional Planning Agency, Tahoe Resource Conservation District and Tahoe Keys Property Owners Association.

The League is now working on targeted studies to assess the efficacy of the bubble curtains and improve the technology.

Learn more about the Tahoe Keys Control Methods Test (CMT)

Seeking a long-term solution to aquatic invasive weeds

Aerial view of the Tahoe Keys
A LONG-TERM SOLUTION: A Test to Address the Tahoe Keys’ Weeds Problem

In January 2022, the Tahoe Regional Planning Agency and Lahontan Water Quality Control Board unanimously approved the Tahoe Keys Control Methods Test (CMT) – a multi-faceted test aimed at addressing the aquatic weed problem in the Tahoe Keys’ lagoons. Learn more about the problem in the Keys through this interactive story map.

As a result of nearly a decade of the League’s leadership, funding and coalition-building efforts, year two of the three-year CMT process wrapped up in fall 2023. You can read a recap of the actions taken in year one and year two in the reports linked below.

Legal update

A lawsuit was filed against the CMT after it was approved in 2022. The main objection focused on the repeated use of herbicides, which was never on the table. EPA-approved herbicides were applied only once in targeted areas blocked off behind protective barriers.

In May 2024, a court ruled in favor of the plaintiffs—in a limited way. The agencies overseeing the CMT have said that the third and final year of testing can go ahead as planned, which includes only non-chemical methods like diver-assisted hand pulling and UV light. That’s good news. Completing the test is critical for protecting the Lake from the spread of invasive weeds. Where the weeds go, the water can go from clear to murky green.

While there may be additional legal steps, the CMT is going forward. The League is watching closely to ensure the CMT goes to plan, and nothing but the weeds are harmed.  

CMT update webinar, June 2024

CMT update webinar, June 2024

The League to Save Lake Tahoe is a key driver and strong supporter of the Control Methods Test because: science clearly shows that the test is safe, aquatic weeds pose a dire threat, the status quo will not solve the problem, and the fate of Lake Tahoe is at stake. Read more about our reasons for support.

Visit tahoekeysweeds.org for more information and keysweedsmanagement.org for the latest updates about the test.

HOW YOU CAN HELP: Become a citizen scientist

You can protect Lake Tahoe from future infestations of aquatic invasive weeds.

Join the Eyes on the Lake volunteer program and use the free Citizen Science Tahoe App to report aquatic invasive species sightings.

While you enjoy Tahoe’s shoreline, use the app to take pictures and tell us what you see. In less than five minutes, you can contribute important information to help Keep Tahoe Blue.

Our weed-fighting work depends on you. Make a donation to support aquatic invasive species control and removal.