SS4.07 Lipids/Fatty Acids in Ecological Research
Date: Tuesday, June 11, 2002
Time: 4:30:00 PM
Location: Saanich
 
ParkS, University of California-Davis, Davis, USA, skpark@ucdavis.edu
Chandra, S, , University of California-Davis, Davis, USA, schandra@ucdavis.edu
Mueller-Navarra, D, C, University of California-Davis, Davis, USA, dcnavarra@ucdavis.edu
Goldman, C, R, University of California-Davis, Davis, USA, crgoldman@ucdavis.edu
 
DIEL AND VERTICAL VARIABILITY OF SESTON FOOD QUALITY AND QUANTITY AT A SMALL SUBALPINE OLIGO-MESOTROPHIC LAKE: ITS IMPLICATIONS TO DIEL VERTICAL MIGRATION
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To examine the influences of seston food quality on zooplankton diel vertical migration, we measured several seston food quality and quantity variables such as particulate carbon, chlorophyll a, fatty acid content, and phosphorus content as well as macrozooplankton distribution over entire water column (6-10 depths) in addition to water temperature and dissolved oxygen during the summer season. Also, Daphnia sp. native to this lake were grown with epilimnetic and hypolimnetic water in both temperatures controlled environment (20 C) and in situ cage to separate the effect of water temperature and seston food conditions. Eicosapentaenoic acid (EPA) content was much lower and carbon to phosphorus ratio (C:P ratios) was much higher in the epilimnion (0-5m) compared to the deep chlorophyll maximum (16-20m). Also, in July and August 2000, seston EPA content was higher and C:P ratios were lower in the epilimnion at nighttime. Projection of Daphnia growth rates showed improved epilimnetic food quality at night, although hypolimnion exhibited much higher Daphnia growth potentials. Once water temperature was considered epilimnion always appeared to support higher potential growth rates. In the temperature controlled incubation, Daphnia showed higher growth with deep chlorophyll maximum water. In the in situ cage incubation, Daphnia showed higher growth in the epilimnion. Daphnia in the migrating treatment exhibited lower growth rate than ones stayed in the epilimnion but much higher than ones stayed in the hypolimnion. These results lead us to believe that Daphnia faces trade-off between a dangerous poor food/warm water and not so dangerous rich food/cold water in Castle Lake.