Intraspecific variation in the nutrient stoichiometry of animals and their waste products ca be substantial, but the factors mediating this variation are unclear. We experimentally manipulated light nutrient supply, and nutrient ratio (N:P) in a field experiment to generate variation in algal quantity an elemental composition, and assessed the stoichiometric responses of juvenile carnivorous fish (bluegill Lepomis macrochirus). Algal quantity (primary production) and stoichiometry (ratios of carbon [C], nitroge [N], and phosphorus [P]) varied greatly in response to manipulations, as did bluegill body and excretio stoichiometry. Algal primary production (PPr) was greatest at high light and high P supply (HL HP) Algal stoichiometry responded in accordance with the light:nutrient hypothesis; that is, C:P ratios wer highest at HL LP and lowest at LL HP. Variation in fish body stoichiometry was strongly related to basa resource supply (PPr), while excretion stoichiometry was driven by both PPr and algal stoichiometry Bluegill growth and body C and N concentrations were highest at HL HN and lowest at LL LN, wherea body P showed the opposite pattern. Thus, bluegill body C:P, C:N, and N:P were highest under HL H and lowest under LL LN. Per capita excretion rates of bluegill were strongly related to body mass an hence were highest at HL HN, where fish grew largest. However, P excretion rates normalized for bod mass increased with phytoplankton P and zooplankton production. In accordance with ecological stoichiometr theory, N:P excretion ratio increased with basal resource (algal) N:P and decreased with estimate bluegill P ingestion. Variation in both body and excretion stoichiometry in this single cohort of fish wa comparable to or exceeded variation observed in other studies of bluegill stoichiometry across multipl ecosystems. Our results illustrate the pronounced intraspecific variation in carnivore nutrient stoichiometr as a function of basal resource quantity and quality.
Bibliographical notePublisher Copyright:
© 2016 Downs et al.
- Ecological stoichiometry
- Light:nutrient hypothesis
- Nutrient ratios