Document: SAN-3-74-19

Seston food quality and zooplankton dynamics in Lake Berryessa, a large reservoir in California.

PARK, S.* ¹, M.T.BRETT ², D.C.MUELLER-NAVARRA ¹, S.CHANDRA ¹, A.MUELLER-SOLGER ¹ and C.R.GOLDMAN ¹

University of California, Davis, CA 95616, USA ¹
University of Washington, Seattle WA 98195 USA ²

Abstract:
We have examined the impacts of food quality on zooplankton dynamics and biomass transfer. Food quality was measured as the essential fatty acid and phosphorus concentration in seston. Changes of the pelagic planktonic food web components in Lake Berryessa were monitored accordingly. During the study period, the particulate carbon concentration was near or above the reported incipient carbon concentration while considerable variability in seston food quality occurred due to dramatic changes in the sestonic composition. The total macrozooplankton to phytoplankton biomass ratios and Daphnia pulex biomass were both high during the springtime, while microbial food web components and the non-Daphnia macrozooplankton fraction were low at that time. The seston essential fatty acid content was strongly correlated with macrozooplankton dynamics and the zooplankton to phytoplankton biomass ratios. Laboratory growth experiments also confirmed that seston food quality largely determined carbon assimilation and growth of Daphnia pulex. Considering both field data and growth experiments, we conclude that seston food quality monitored as essential fatty acid and phosphorus content was a good predictor for zooplankton dynamics and biomass transfer in springtime while factors other than food quality may have affected Daphnia pulex and zooplankton dynamics during the other seasons in Lake Berryessa.

Keywords: Essential fatty acids, Phosphorus, Food quality index, Zooplankton dynamics, Biomass transfer

This abstract is being presented at: 11:00 AM in session:
Oral Session #54: Lake Ecology.