New science-based roadmap to protect Lake Tahoe from aquatic invaders

Lake Tahoe’s public agencies have teamed with scientists, marinas and lakefront homeowners on a new strategy to protect the highly impacted nearshore ecosystems and to combat invasive species that threaten the lake’s famed clarity and $5 billion economy.

The focus of the new funding and strategy is Tahoe’s nearshore, an area up to about 50 feet deep, where Tahoe’s three million annual visitors now interface with more than 30 non-native species, including Asian clams, Eurasian water milfoil and several warm-water fish. These species disturb Tahoe’s native ecosystem and food chain, impair the lake’s clarity and clog its marinas, piers, and boat propellers.

The strategy, outlined in a new implementation plan to control aquatic invasive species at Lake Tahoe, is a joint effort between University of Nevada, Reno scientists and the Tahoe Resource Conservation District. The plan concludes that it’s not too late to control or eradicate several of Tahoe’s most noxious species, and provides a roadmap for funding the highest priority projects.

“With a serious and sustained effort, we can protect Lake Tahoe’s native species and the health of Tahoe shorezones from unwanted invasive species,” Sudeep Chandra, biologist and limnologist from the University of Nevada, Reno and co-author of the plan, said.

“Our rigorous aquatic invasive species prevention program at Lake Tahoe has prevented the introduction of any new aquatic invaders since its launch in 2009 and has become a model for the rest of the nation,” said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency. “This implementation plan is a critically important, science-based plan for us to aggressively fight harmful aquatic invaders already in Lake Tahoe – to stop them from causing any more damage to our unique environment or to our recreation-based economy that depends on its health.”

Of the nearly 30 non-native aquatic species established in the Lake Tahoe watershed since the 1800s this report targets three for feasible action: Eurasian water milfoil, curly leaf pondweed and warm-water fish. Identified for potential control or eradication actions are the signal crayfish and the American bullfrog. Asian clams and mysid shrimp, established at several locations at the south shore of the lake, are identified as having no feasible control options at this time, but pursuit of possible future actions should continue.

Chandra, director of the Aquatics Ecosystems Analysis Laboratory, and his team, led by co-author and University of Nevada, Reno biologist Marion Wittmann, ranked the lake’s 28 known nearshore invasive sites to help the agencies and their private partners make the most cost-effective investment decisions. The science team then submitted their findings to a national panel of experts for a rigorous scientific review and to key stakeholder groups to receive critical feedback.

“Ensuring scientific quality as well as buy-in from the users of this plan are crucial elements for a successful invasive species removal program,” Wittmann said.

The approach calls for aggressive removal projects at the basin’s most popular marinas, including Tahoe Keys and Ski Run and Lakeside Marinas, where warm water and boating facilities provide a home for invasives to thrive and spread. Other targeted areas include the lake’s outlet in Tahoe City and popular beaches at Meeks Bay, Crystal Bay and South Lake Tahoe.

“This strategy is essential not only to guide investment decisions and on the ground control actions but to bring together Tahoe’s key public and private organizations to jointly address and fund these efforts,” said Kim Boyd, district manager of the Tahoe Resource Conservation District. “The nearshore is where the public connects with the lake, so it deserves top priority for funding and attention.”

The plan was funded through the California Tahoe Conservancy, a state agency, in large part using fees paid by Tahoe lakefront homeowners and marinas in California.

“This strategy demonstrates how a public/private partnership will be essential to control the growing threat to the lake’s clarity and the quality of our lakefront beaches, homes and marinas,” Jan Brisco, executive director of the Tahoe Lakefront Owners Association, said.

The lakefront homeowners were key supporters of a recent California state law, SB630, which redirects nearly $1 million in state fees for buoys and piers from the state’s general fund to Tahoe-specific projects. This year money from the fund will support nearshore water-quality monitoring and aquatic invasive species study and treatment, and will help establish a bi-state science council.

The invasives plan is part of a larger collaborative effort led by the Tahoe Regional Planning Agency to control and monitor invasive species around the lake and the Tahoe Resource Conservation District to inspect all boats entering Lake Tahoe to limit new introductions of invasives.

The implementation plan supports the goals of the Lake Tahoe Aquatic Invasive Species Management Plan developed by the Aquatic Nuisance Species Task Force, which is one of several approaches to combat the onslaught of invasive species, such as a program being coordinated by the League to Save Lake Tahoe using volunteers to identify and survey the spread of aquatic invasives around the lake.

“This implementation plan is a direct extension of the AIS Management Plan, giving boots-on-the-ground guidance to agencies,” Chandra, said.

“This exciting roadmap is a key piece of the Basin’s comprehensive strategy,” Marchetta said. “Coupled with other programs such as the integrated weed management program under development for the Tahoe Keys, the successful work to remove Eurasian watermilfoil from Emerald Bay and the recommendations and new strategies outlined for monitoring, resource evaluation and research to fill data gaps, this plan will help guide Tahoe policies for many years.”

— Mike Wolterbeek is a Communications Officer for the University of Nevada, Reno. He can be reached at mwolterbeek@unr.edu