CS39A Zooplankton - Feeding, Reproduction, Growth and Molecular Diversity
Date: Tuesday, June 11, 2002
Time: 2:15:00 PM
Location: View Royal
 
SpaakP, Swiss Fed. Inst. Env. Sci. Technol. (EAWAG), Duebendorf, Switzerland, spaak@eawag.ch
Keller, B, , Swiss Fed. Inst. Env. Sci. Technol. (EAWAG), Duebendorf, Switzerland, barbara.keller@eawag.ch
Rudis, M, , Swiss Fed. Inst. Env. Sci. Technol. (EAWAG), Duebendorf, Switzerland, michael.rudis@excite.com
 
MICROEVOLUTION IN DAPHNIA THROUGH CHANGING PHOSPHORUS CONDITIONS REVEALED BY DORMANT EGGS
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Many polluted lakes in Europe are being restored and phosphorus concentrations have dropped dramatically in these lakes. We studied the selection response of Daphnia galeata to decreased phosphorus in Lake Greifensee, Switzerland from 1972 to 2000. Distinct genotypes of D. galeata were hatched from diapausing eggs extracted from six different time horizons in the dated sediments. We compared growth and survival of D. galeata reared on high-P and low-P algae to investigate whether Daphnia have evolved to grow better on Phosphorus -limited algae. Our results indicate that significant shifts have occurred in the genetic structure of this population, which parallel concomitant shifts in the trophic state of Lake Greifensee during the past 30 years. Furthermore, significant differences in survival were found among daphnids hatched from different sediment depths reared on low-P algae. We discuss our results in relation to differences between the D. galeata population in two 'habitats': the dormant population in the sediment and the ones observed in presently in the lake.