Brett, M. T. University of Washington, mtbrett@u.washington.edu
Mčller-Navarra, D. C. University of California (Davis), doerthe.navarra@dkrz.de
Park, S. University of California (Davis), skpark@ucdavis.edu

 
AN EMPIRICAL ANALYSIS OF MINERAL P LIMITATION'S IMPACT ON ALGAL FOOD QUALITY FOR FRESHWATER ZOOPLANKTON
 
The mineral phosphorus (P) limitation of zooplankton production hypothesis is one of the more popular hypotheses in limnology. We conducted a quantitative analysis of 246 observations of lake seston carbon to phosphorus (C/P) elemental ratios and 91 observations of daphnid zooplankton growth responses to nutrient limited algal diets. 34% of the published lake seston C/P ratios exceeded the critical threshold of 300. Recent experimental evidence suggests direct mineral P limitation of Daphnia growth is real when they consume severely P limited (C/P │ 1000) green algae. Daphnia growth when feeding on nutrient limited algae is consistently reduced at algal C/P ratios above 300, however, this reduction is only about 64% as strong as the theoretically expected. After correcting for phosphorus content large differences in food quality were found between the major algal taxa, with diatoms and cryptophytes high, chlorophytes intermediate, and cyanophytes low food quality. A Monte Carlo simulation based on these results showed algal taxonomic affiliation explained 6 times more variability in daphnid growth rates than did algal C/P across a realistic range of C/P ratios. These results support the mineral P limitation hypothesis, but they also suggest other factors may be the main determinants of algal food quality in most lakes. SS21 Oral
 
Day: Wednesday, Feb. 3
Time: 09:30 - 09:45am
Location: Hilton of Santa Fe
 
Code: SS21WE0930H