Prey element stoichiometry controls ecological fitness of the flagellate Ochromonas danica

摘要

ABSTRACT: In aquatic systems, the protist-bacteria consumer-resource interaction is one of the few interactions that link and regulate the flow of dissolved nutrients to higher trophic levels. While this interaction is well characterized from the perspective of top-down control of bacteria, less understood is how the interaction may regulate consumer success. Here, we consider the protist-bacteria consumer-resource interaction and explore relationships among food quality (measured as ratios of C:N, C:P, or N:P), prey type (measured by prey-size and taxonomic affiliation), and consumer success (measured by growth rate). We use a model consumer, the flagellate Ochromonas danica, and a variety of bacterial species as resources. Rates at which prey were ingested corresponded to prey quality for metrics of food quality based on C (C:N and C:P). Prey quality also strongly influenced consumer fitness. A large imbalance between the element ratio of the consumer and that of its prey had a negative impact on consumer fitness, particularly when excess C or excess N was consumed. Prey type, as a phylogenetic group of bacteria, also influenced consumer success. Betaproteobacteria were readily consumed but failed to support consumer growth, mainly as a result of a nutrient imbalance between consumer and resource.