The Lahontan Water Board has funded UC Davis to perform attached algae (periphyton) monitoring for close to 30 years. The program includes routine sampling at nine sites distributed around the lake and an annual lake perimeter (synoptic) survey to evaluate conditions during the spring period of maximum growth (See 2016 Periphyton trend Analysis). Contrary to public and manager perception, a 2016 data analysis identified neither significant lake-wide or site-scale trends in periphyton growth. In fact, the analysis identified only a slight increase at the Pineland and Incline West sites over this time.

To address the issue that monitoring protocols are not robust enough to detect changes and trends in periphyton biomass, UCD proposed revisions to the monitoring program protocols. In January of 2020, the Nearshore Agency Working Group tasked the Tahoe Science Advisory Council (Science Council) to conduct a peer review of the proposed monitoring protocols. The reviewers concluded the proposed protocols are consistent with best practices for other lakes. Revised protocols are currently being piloted at several locations to facilitate results comparison of old and new protocols.  

In subsequent discussions, Science Council members theorized the perception of increased algal growth may be a result of changes in metaphyton (filamentous algae) growth. Unattached to the lakebed, these filamentous algae tend to get washed onshore, fouling the recreation experience of beachgoers. In the summer of 2020, UCD completed a feasibility study of several remote sensing platforms to characterize metaphyton populations. The study concluded that monitoring metaphyton was feasible at a nominal additional cost to the periphyton monitoring program.   

As such, the Nearshore Agency Working Group in coordination with science partners are working to develop an Integrated Algal Monitoring program that measures status and detects trends in periphyton and metaphyton populations at locations that are tied to Lake Tahoe’s recreational beneficial uses.