No Project associated with this Finding

The accumulation of periphyton (attached algae) on natural rock surfaces and other substrates
is a striking indicator of Lake Tahoe’s water quality. Periphyton monitoring in Lake Tahoe has
occurred since 1982, with near-continuous monitoring occurring since 2000. Statistical
analyses found no significant lake-wide trends in periphyton biomass from 1982-2015, which
contrasts with some anecdotal evidence of residents. The reviewers generally agreed that the
locations and methods used for sampling status and trends were sufficient. However, there was
some concern about the bias that could arise from sampling a single depth (0.5 m) in long-term
trend analyses. The reviewers agreed that suggested changes to the monitoring program would
improve its capabilities to track status and trends. Specific ways to improve the proposed
sampling methods and spatial sampling scheme were suggested by the reviewers. Finally, the
reviewers concluded that the monitoring program was consistent with best practices for similar
lakes. They noted, however, that overriding aesthetic concerns may necessitate alternative
monitoring metrics based on visual assessments that complement the proposed monitoring
plan.