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Sensitivity of herbivorous zooplankton to phosphorus‐deficient diets: Testing stoichiometric theory and the growth rate hypothesis
Author(s) -
Ferrão-Filho Aloysio da S.,
Tessier Alan J.,
DeMott William R.
Publication year - 2007
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2007.52.1.0407
Subject(s) - daphnia , zooplankton , biology , ecological stoichiometry , algae , cladocera , branchiopoda , assimilation (phonology) , daphnia magna , zoology , herbivore , nutrient , ecology , chemistry , linguistics , philosophy , organic chemistry , toxicity
Stoichiometry and growth rate variation are related aspects of the ecology and evolution of consumer‐resource interactions. In zooplankton, these concepts have been explored primarily in a few species of Daphnia . We used growth bioassays and changes in animal P content to quantify the sensitivity of four herbivorous cladoceran species to algal resources representing a gradient in C: P ratios ranging from 140 to 1,000, offered at both low and high food levels. Supplements of phosphate, Synechococcus , or P‐sufficient algae were used to test for P, energy, and fatty acid limitation. Phosphorus assimilation was estimated by isotope techniques (32P) to test the hypothesis of digestion resistance in P‐limited algae. The cladoceran species differed in sensitivity to P deficiency at both low and high food levels, although sensitivity was less at low food. The P content of the two Daphnia species changed substantially along the C: P ratio gradient, contradicting the notion of strict homeostasis, whereas the two other cladoceran species showed tight P homeostasis. Consistent with stoichiometric theory, the two species with the highest P content were also more sensitive to P deficiency. Growth rate was related to P content across the four species at the high food level and at low C: P ratios, supporting the growth rate hypothesis. The addition of supplements to P deficient algae improved animal's growth rates, showing both P and energy limitation, but no evidence for fatty acid limitation. Lower assimilation efficiency for P‐deficient algae suggests that digestion resistance can be a factor in the food quality of P‐deficient resources.