Document: MAR-3-56-16
Temporal variability in physical-chemical coupling to algal quality and zooplankton production dynamics.
SCHEUERELL, M.D.*
University of Washington, Seattle, WA, 98195 1
Abstract:
Understanding how the physical and chemical features of ecosystems affect producer-consumer interactions remains an important goal of ecology. Recent models of lakes suggest that interactions between light and nutrient availability in the mixed layer determine the C:P ratio of phytoplankton, and hence, food quality for herbivorous zooplankton. Similarly, increases in algal food quality have also been shown to positively affect zooplankton growth and reproductive rates. However, these studies have mostly concentrated on explaining variation among lakes over relatively short time periods and have not evaluated the long-term dynamics in the physical-chemical forcing of algal quality and zooplankton production in individual systems. Using dynamic linear models to analyze a high-resolution, 22-year time series from Lake Washington, I investigated the effect of the light:nutrient ratio on algal food quality (measured as the algal chlorophyll:biovolume ratio) and the subsequent effect of this food quality on zooplankton production. The ratio of light to total phosphorus generally had a positive effect on the ratio of phytoplankton chlorophyll a to biovolume, but the effect was negative in some years. I also detected a positive relationship between algal food quality and Daphnia birth rates. In both cases, I also found strong seasonal differences with the largest effects occurring in mid-summer and the lowest in winter. These results demonstrate strong intra- and inter-seasonal variation in the forcing of light and nutrient regimes on algal food quality and its subsequent effect on zooplankton production dynamics.
Keywords: producer-consumer interactions, physical-chemical coupling, time series, algal food quality, Daphnia
This abstract is being presented at: 2:30 PM in session:
Oral Session #47: Zooplankton Ecology.