2018 Pilot Study: Monitoring Summer Metaphyton Growth along the South and Southeast Shore of Lake Tahoe

No Project associated with this Finding

Finding Details

In the summers of 2015-2017, a pilot study was done by the UC Davis Tahoe Environmental Research Center (TERC) to develop and test methods that could be used to monitor metaphyton algae in the nearshore of Lake Tahoe. Metaphyton is algae which is neither strictly attached to a substrate (like periphyton) nor truly planktonic (like phytoplankton). In Lake Tahoe, the metaphyton is typically composed of aggregations of green filamentous algae ranging from small clumps of algae rolling between sand ripples on the shallow lake bottom, to larger clouds of algae hovering above, or resting on the bottom. Undesirable levels of algae can develop resulting in clouding of the nearshore waters and its deposition along the shore. Once on the shore, it forms accumulations that eventually decompose, but in the process, it can be both extremely unsightly and malodorous. Anecdotal evidence suggests that levels of metaphyton may have increased in recent years; however, little data has been collected. There currently is no consistent methodology or data collection effort on the occurrence and amounts of metaphyton in the nearshore of Lake Tahoe.

The emphasis in this study was on testing of field and lab methods that would be appropriate for monitoring metaphyton at select sites around the lake. The Lake Tahoe Nearshore Evaluation and Monitoring Framework report (Heyvaert et al., 2013) identified a need to know more about metaphyton and recommended that a few metaphyton monitoring sites should be included as part of periphyton monitoring, especially along the south shore region during summer. For sites such as popular beaches where shoreline users may consider metaphyton undesirable, such monitoring would provide baseline data to begin to assess trends. Such methods would also provide a means to study the potential causes of heavy metaphyton growth (i.e. nutrient loading, lake temperature, Asian clam presence and lake level fluctuation). For regional or lake-wide assessments of metaphyton, and for assessing the contributions of large patches of metaphyton along shore, additional methods such as aerial imaging will likely be needed. An assessment of regional metaphyton monitoring methods is planned in a follow-up study for NDSL to be done in the summers of 2018-2019. Methods found to be effective for metaphyton monitoring in the current study could be used in concert with other methods for regional and lake-wide metaphyton monitoring.