No Project associated with this Finding

Eurasian Watermilfoil

Lake Tahoe’s nearshore area contains few aquatic plants with the exception of a native water milfoil species and Elodea Canadensis. The Eurasian watermilfoil (Myriolphyllum spicatum) is the main invasive plant to establish in Lake Tahoe. The plant fragments, and propagules of the fragments can colonize and grow when attached to substrate. To date many locations of this nonnative plants are largely within marinas, closed embayments, or waters where there is little physical mixing (e.g. West end of Emerald Bay). Since the first surveys were conducted in the mid-1990s by the USDA ARS laboratory confirming the presence of water milfoil, there has been an expansion over time from the south end of the lake to the northeast and west shores of Lake Tahoe (Figure 16-1).

Curly Leaf Pondweed

In 2003, a more aggressive plant was noted in the Tahoe Keys. Curly leaf pondweed (Potomageton crispus) can colonize open water areas and is rapidly moving to new locations in the South Shore. The curly leaf pondweed has established within certain fingers of the Tahoe Keys, dominating the biomass while in other locations it is not dominant. Research is ongoing to determine the life history attributes of curly leaf pondweed within the ultraoligotrophic waters of Lake Tahoe (UC Davis, unpublished information).

Recommended Monitoring Plan

As a result of the aggressive spread of the water milfoil in the last 17 years, the potential for dominance of the open waters by curly leaf pondweed, and the potential for introduction of new plant taxa through the transport of boats into Lake Tahoe, we recommend conducting a snorkel survey of nearshore waters of the lake every 2-3 years. The focus of the survey should be along a 2-5 meter contour line and within marinas around the lake. The presence/absence of plant beds and identification of plants should occur at each location. Marinas should be included in this analysis since boaters are likely to either introduce and/ or move new plant taxa, allowing for their establishment. The 2011 survey should be used as a base survey to establish monitoring locations.

For additional information, view the Lake Tahoe Nearshore Evaluation and Monitoring Framework below.