PARENT SESSION
Contributed Oral Session 39: Physiology: Respiration, Sap Flow, and Growth
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 513 E, Level 5, Palais des congrès de Montréal
Threshold carbon: Phosphorus ratios of aquatic consumers: Effects of growth rate, metabolism, and body elemental composition.
Frost, Paul*,1, Benstead, Jonathan2, Cross, Wyatt3, Hillebrand, Helmut4, Larson, James1, MacKenzie, Cameron , Xenopoulos, Marguerite5, Yoshida, Takehito 6, 1 University of Notre Dame, Notre Dame, IN, USA2 Marine Biological Laboratory, Woods Hole, MA, USA3 University of Georgia, Athens, GA, USA4 University of Cologne, Köln, Germany5 Trent University, Peterborough, Canada6 Cornell University, Ithaca, NY
ABSTRACT- Threshold elemental ratios for growth have been previously calculated for a limited number of freshwater taxa (i.e., Daphnia and Ephemerella). We calculated the carbon:phosphorus (C:P) threshold ratio of growth for a wide array of freshwater and marine organisms using a mass balance model and information on animal elemental composition and energetics. While the model dictates that threshold C:P ratios will be positively related to body C:P ratios and negatively related to mass specific ingestion, the relative strength of these effects is unknown. Data from a variety of aquatic taxa, including fish, crustaceans, mollusks and insects across a wide range of body mass, were collected from the literature to parameterize the model. Initial results from thirty taxa showed a wide range in the threshold C:P ratio (100-3000) that was positively related to consumer body C:P ratio. Differences in carbon metabolism found among taxa also affected threshold C:P ratios at a given body C:P ratio. Fast growing organisms had low threshold C:P ratios whereas slow growing consumers showed a range of threshold values. Our results show that sensitivity to P-poor food should vary widely among taxa due to considerable interspecific variation in growth rate, body C:P content, and carbon metabolism.
Key words: ecological stoichiometry, bioenergetics, metabolism, growth rate