Document: SPE-3-52-16

Stoichiometric gradients influence community composition of consumers.

HALL, S.R.*

University of Chicago, Chicago, IL 60637 ¹

Abstract:
Recent experiments suggest that elemental composition of resources may influence population dynamics of consumers. Key findings from this body of work show that elemental composition of food (i.e., food quality) can affect growth efficiency of consumers, and that consumers can be nutrient limited. Nevertheless, to date there is no long-term experimental data to determine if consumer species are more abundant in environments in which the elemental composition of their food more closely matches their own composition. To address this question, I experimentally created a light (using shade cloth and duckweeds):phosphorus gradient in semi-natural pond mesocosms to manipulate the ratio of carbon:phosphorus of seston. Shading reduced ecosystem-level productivity and increased the relative availability of inorganic nutrients (phosphate, nitrate, and ammonium), indicating increased relative light limitation of autotrophs. Although each mesocosm started initially with similar, species-diverse communities of zooplankton, species with high C:P body composition (calanoid copepods) were most abundant in treatments with high light:phosphorus ratios, and species with low C:P body composition (daphnid cladocerans) were more abundant (although variable) in treatments with low light:phosphorus ratios. These results suggest that variation in food quality, mediated through mechanisms involving elemental constitution of consumers and resources, can influence consumer composition.

Keywords: Elemental ratios, food quality, consumer resource interactions, productivity, light, zooplankton

This abstract is being presented at: 9:00 AM in session:
Oral Session #37: Phytoplankton.