Schwalbach, M. S. University of Minnesota-Twin Cities,
Sterner, R. S. University of Minnesota-Twin Cities,

Due to variations in nutrient availability and light levels, distinct algal regimes develop in stratified lakes. High quality (phosphorus-rich) algal food sources are located in deeper layers in low quantites, and poor quality (phosphorus-deficient) algal food sources are located in surface waters in high quanities. As a result of this algal distribution, zooplankton are exposed to varying quantities and qualities of food when they vertically migrate. The temporal effect of fluctuating mineral nutrient supply on zooplankton growth rate was studied. To simulate migratory conditions, female Daphnia magna neonates were incubated in high quality food for varying lengths of time. At the end of this incubation period, the animals were transferred into low quality food for the remainder of the twenty-four hour period. After six days, the animals were dried overnight and weighed to determine growth rate and biomass. Results of this experiment revealed a growth rate maximum at approximately five hours of exposure to high quality food. The maximum occurs after a short incubation period due to Daphnia's ability to store excess phosphorus. Therefore, despite migrating through regions of fluctuating food regimes, Daphnia can sustain maximum growth rates while spending only a short amount of time in phosphorus-rich environments.
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
Code: SS49TU0070S