Programa de Pós-Graduação em Ecologia e Evolução, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier, 524, Maracanã, Rio de Janeiro, RJ, CEP 20550-013, Brazil.
Department of Natural Resources and the Environment, Cornell University, Ithaca, NY, USA.
Sci Rep. 2022 Sep 1;12(1):14844. doi: 10.1038/s41598-022-19149-w.
Ecological Stoichiometry (ES) and the Metabolic Theory of Ecology (MTE) are the main theories used to explain consumers' nutrient recycling. ES posits that imbalances between an animal's body and its diet stoichiometry determine its nutrient excretion rates, whereas the MTE predicts that excretion reflects metabolic activity arising from body size and temperature. We measured nitrogen, phosphorus and N:P excretion, body N:P stoichiometry, body size, and temperature for 12 fish species from a Brazilian stream. We fitted competing models reflecting different combinations of ES (body N:P, armor classification, diet group) and MTE (body size, temperature) variables. Only body size predicted P excretion rates, while N excretion was predicted by body size and time of day. N:P excretion was not explained by any variable. There was no interspecific difference in size-scaling coefficients neither for N nor for P. Fitted size scaling coefficients were lower than the MTE prediction of 0.75 for N (0.58), and for P (0.56). We conclude that differences in nutrient excretion among species within a shared environment primarily reflect contrasts in metabolic rates arising from body size, rather than disparities between consumer and resource stoichiometry. Our findings support the MTE as the primary framework for predicting nutrient excretion rates.
生态化学计量学 (ES) 和生态代谢理论 (MTE) 是用来解释消费者营养回收的主要理论。ES 假设动物体内与其饮食化学计量之间的不平衡决定了其营养排泄率，而 MTE 预测排泄反映了来自体型和温度的代谢活动。我们测量了来自巴西溪流的 12 种鱼类的氮、磷和 N:P 排泄、体 N:P 化学计量、体型和温度。我们拟合了反映 ES（体 N:P、盔甲分类、饮食组）和 MTE（体型、温度）变量不同组合的竞争模型。只有体型预测了 P 排泄率，而 N 排泄则由体型和一天中的时间来预测。N:P 排泄不受任何变量解释。无论是 N 还是 P，种间大小缩放系数都没有差异。拟合的大小缩放系数均低于 MTE 对 N（0.58）和 P（0.56）的预测值 0.75。我们得出的结论是，在共享环境中，物种之间的营养排泄差异主要反映了来自体型的代谢率差异，而不是消费者和资源化学计量之间的差异。我们的研究结果支持 MTE 作为预测营养排泄率的主要框架。
