USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Understanding the decline of deepwater sensitive species in Lake Tahoe: What is responsible, eutrophication or species invasions?

Principal Investigators:
Sudeep Chandra, University of Nevada-Reno
Eliska Rejmankova, University of California-Davis
John Reuter, University of California-Davis

Proposal [pdf]

Final Report [pdf]

Project Summary

A comparison of historical and contemporary benthic surveys has shown a large decline in bottom invertebrate and macrophyte occurrence in the deepwater environment of Lake Tahoe (Caires et al. 2013). The decline in macrophytes and invertebrates may be directly or indirectly related to reductions in water clarity over the past 4 decades and invasive species introductions. Two of Lake Tahoe’s unique bottom species (the deepwater stonefly Capnia lacustra and the blind amphipod Stygobromus spp.), found nowhere else in the world, are at high risk given their significant reduction since the 1960s.

We examine the spatial distribution of deepwater special status plants (Chara and moss) and invertebrates (C. lacustra and Stygobromus spp.). In doing so, we also gather information about the biology and ecology of these taxa. Specifically, we provide information about the life cycles of special status plants and invertebrates and feeding strategies of endemic invertebrates.

We also measure the photosynthetic rates of Chara, a native deepwater macroalgae, at varying light conditions and relate observed photosynthetic responses to subsurface irradiance data from Lake Tahoe in order to understand the depths at which light is limiting for Chara. We describe important relationships between the distribution of native plants and endemic invertebrates and physical characteristics of the lake. Monitoring of relatively longlived organisms such as aquatic plants and invertebrates provides an important biological indicator of the overall health of the system, one that has received little attention in Lake Tahoe.