Stoichiometric implications of a biphasic life cycle

• Published in: Oecologia Vol. 180; no. 3; pp. 853 - 863
• Main Authors: Tiegs, Scott D, Berven, Keith A, Carmack, Douglas J, Capps, Krista A
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2016; Springer Science + Business Media; Springer; Springer Nature B.V
• Subjects: adults; Animals; Anura; Biomass; Biomedical and Life Sciences; carbon; Carbon - metabolism; Carbon Cycle; Ecology; Ecosystem; ECOSYSTEM ECOLOGY – ORIGINAL RESEARCH; Ecosystems; eggs; energy; excreta; Excretion; Frogs; Hydrology/Water Resources; Larva; Larvae; Larval development; Life Cycle Stages; Life cycles; Life Sciences; Mineralization; nitrogen; Nitrogen - metabolism; Nitrogen Cycle; Nutrients; ontogeny; phosphorus; Phosphorus - metabolism; Physiological aspects; Physiology; Plant Sciences; Rana sylvatica; Ranidae - growth & development; Ranidae - metabolism; stoichiometry; tissues; vertebrates; Nutrient mineralization; Development; Phosphorus; Nutrient excretion; Ontogeny; Ecological stoichiometry; Nitrogen; Amphibian; Rana sylvatica
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-015-3504-2

Animals mediate flows of elements and energy in ecosystems through processes such as nutrient sequestration in body tissues, and mineralization through excretion. For taxa with biphasic life cycles, the dramatic shifts in anatomy and physiology that occur during ontogeny are expected to be accompanied by changes in body and excreta stoichiometry, but remain little-explored, especially in vertebrates. Here we tested stoichiometric hypotheses related to the bodies and excreta of the wood frog (Lithobates sylvaticus) across life stages and during larval development. Per-capita rates of nitrogen (N) and phosphorus (P) excretion varied widely during larval ontogeny, followed unimodal patterns, and peaked midway through development (Taylor–Kollros stages XV and XII, respectively). Larval mass did not increase steadily during development but peaked at stage XVII and declined until the termination of the experiment at stage XXII. Mass-specific N and P excretion rates of the larvae decreased exponentially during development. When coupled with population-biomass estimates, population-level excretion rates were greatest at stages VIII–X. Percent carbon (C), N, and C:N of body tissue showed weak trends across major life stages; body P and C:P, however, increased sixfold during development from egg to adult. Our results demonstrate that intraspecific ontogenic changes in nutrient contents of excretion and body tissues can be significant, and that N and P are not always excreted proportionally throughout life cycles. These results highlight the dynamic roles that species play in ecosystems, and how the morphological and physiological changes that accompany ontogeny can influence ecosystem-level processes.