title: Metabolic theory and taxonomic identity predict nutrient recycling in a diverse food web.
abstract: Reconciling the degree to which ecological processes are generalizable among taxa and ecosystems, or contingent on the identity of interacting species, remains a critical challenge in ecology. Ecological stoichiometry (EST) and metabolic theory of ecology (MTE) are theoretical approaches used to evaluate how consumers mediate nutrient dynamics and energy flow through ecosystems. Recent theoretical work has explored the utility of these theories, but empirical tests in species-rich ecological communities remain scarce. Here we use an unprecedented dataset collected from fishes and dominant invertebrates (n = 900) in a diverse subtropical coastal marine community (50 families, 72 genera, 102 species; body mass range: 0.04-2,597 g) to test the utility of EST and MTE in predicting excretion rates of nitrogen (E(N)), phosphorus (E(P)), and their ratio (E(NP)). Body mass explained a large amount of the variation in EN and EP but not E(NP). Strong evidence in support of the MTE 3/4 allometric scaling coefficient was found for E(P), and for E(N) only after accounting for variation in excretion rates among taxa. In all cases, including taxonomy in models substantially improved model performance, highlighting the importance of species identity for this ecosystem function. Body nutrient content and trophic position explained little of the variation in E(N), E(P), or E(NP), indicating limited applicability of basic predictors of EST. These results highlight the overriding importance of MTE for predicting nutrient flow through organisms, but emphasize that these relationships still fall short of explaining the unique effects certain species can have on ecological processes.
authors: School of Aquatic and Fisheries Science, University of Washington, Seattle, WA 98105; zopelote@gmail.com.
authors: Jacob Edward
authors: JE
authors: Allgeier
authors: Odum School of Ecology, University of Georgia, Athens, GA 30602; and.
authors: Seth J
authors: SJ
authors: Wenger
authors: Odum School of Ecology, University of Georgia, Athens, GA 30602; and.
authors: Amy D
authors: http://orcid.org/0000-0003-4299-9353
authors: AD
authors: Rosemond
authors: School of Aquatic and Fisheries Science, University of Washington, Seattle, WA 98105;
authors: Daniel E
authors: DE
authors: Schindler
authors: Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695.
authors: Craig A
authors: CA
authors: Layman
mesh_terms: D000818:Animals; D001835:Body Weight; D003672:Defecation / Q000502:physiology*; D005399:Fishes / Q000378:metabolism / Q000502:physiology*; D020387:Food Chain; D007448:Invertebrates / Q000378:metabolism / Q000502:physiology*; D016014:Linear Models; D008386:Marine Biology / Q000379:methods; D053858:Metabolic Networks and Pathways / Q000502:physiology*; D008954:Models, Biological; D013045:Species Specificity
keywords: coastal ecosystems; consumer-mediated nutrient cycling; ecological stoichiometry; nitrogen; phosphorus