No Project associated with this Finding

The impetus for this work stemmed from many conversations from 2018-2022 by the Tahoe Science Advisory Council and from scientific papers (Chandra et al. 2024) and reports (Cortes et al. 2022) that recommended filling a knowledge gap related to zooplankton dynamics in Lake Tahoe. In lakes, zooplankton can play an important role in transferring carbon (energy) from the lower food web (bacterial and algae) to higher-level consumers like fishes and amphibians, influencing the structure and function of the microbial and phytoplankton part of the food web through the excretion of dissolved organic carbon and nutrients, and grazing particulate matter through feeding. While published studies from Lake Tahoe have not supported the last point, it may be important in moderately productive parts of the lake, like Emerald Bay (Bess et al. 2021; Chandra et al. 2024), the lake’s nearshore, or marinas.

An essential component of the Lake Tahoe clarity model, zooplankton-derived estimations inserted into the model are from 1-2 locations within the lake collected through unfunded efforts by UC Davis. In addition, there is no contemporary information about the lake’s microzooplankton dynamics (i.e., rotifers and ciliates), and there is no understanding of zooplankton dynamics in vertical and horizontal space (nearshore to offshore). Previous snapshot studies captured some aspects of the variation of zooplankton in space and time. These studies were conducted when the lake was in a different state regarding clarity and algal production. The historical studies show a significant variation of invasive mysid shrimp (Mysis diluviana) and native zooplankton, suggesting ‘patchiness’ in vertical space, perhaps through daily migrations of zooplankton or due to methodological issues at the time of the study or variation within horizontal space (Goldman, 1974; Rybock, 1978, Morgan, 1981; Burgi, et al. 1993). Based on literature from other large lakes, we expect variation in zooplankton dynamics across space and time as zooplankton may migrate in the day and night. Hence, quantifying the contemporary composition and densities within Lake Tahoe could serve as important updates to model inputs (e.g., mass balance, statistical) that try to explain why Lake Tahoe’s clarity is changing over time. This project implemented a comprehensive sampling across seasons in time and space to evaluate the dynamics of zooplankton over seasons and quantified the environmental variation in clarity and water quality across the lake. In addition, we investigated the community composition of microzooplankton, vertical migration patterns, and ecological effects of zooplankton on particles across nearshore and pelagic environments.