Selective Feeding Determines Patterns of Nutrient Release by Stream Invertebrates

James M. Hood, Camille McNeely, Jacques C Finlay, Robert W Sterner

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

One common stoichiometric approach to predicting patterns of nutrient release (excretion + egestion) by animals in aquatic ecosystems is to base predictions on elemental mass-balance constrained by homeostatic maintenance. An easily measured resource composite (i.e., seston, epilithon, or leaf litter) often is used to represent ingested stoichiometry, but whether such a composite is a good indicator of food actually ingested is a relatively unexplored assumption. We examined the application of a stoichiometric model to the diets of 4 generalist stream invertebrates. We fed 3 trichopteran and 1 amphipod taxa rations consisting of cultured algae, stream epilithon, and several species of conditioned leaf litter. The rations ranged widely in C:N from 10 to 69 (molar) and in C: P from 165 to 3500. After a 2-d feeding period, we measured NH4+ and PO43- excretion, and C, N, and P egestion rates. The relationships observed between the stoichiometries of release and ration were unexpected. Total N: P release rates conformed to stoichiometric predictions for only 1 taxon. Excretion and egestion rates and ratios were generally similar across diets and rarely varied with ration stoichiometry. These patterns were the result of smaller-than-expected responses to leaf-litter rations, which were the most imbalanced relative to body stoichiometry. Analysis of the C:N stoichiometry of foregut material for 2 taxa showed selective ingestion of an N-rich fraction of leaf litter, in 1 case reducing an apparent 8.4:1 C:N imbalance between diet and body composition to 1.5:1. Our results show that selective feeding can reduce potential stoichiometric imbalances, altering patterns of nutrient release relative to expectations based on bulk-diet stoichiometry. Assuming that stream invertebrates consume materials stoichiometrically similar to a resource composite can obscure understanding of stoichiometric imbalances and the role of invertebrates in nutrient cycles.

Original languageEnglish (US)
Pages (from-to)1093-1107
Number of pages15
JournalFreshwater Science
Volume33
Issue number4
DOIs
StatePublished - Jan 1 2014

Fingerprint

stoichiometry
invertebrate
invertebrates
leaf litter
plant litter
nutrient
composite materials
nutrients
excretion
epilithon
Epilithon
diet
algae
foregut
prediction
seston
resource
amphipod
generalist
aquatic ecosystem

Keywords

  • consumer-driven nutrient recycling
  • ecological stoichiometry
  • egestion
  • excretion
  • selective feeding
  • streams

Cite this

Selective Feeding Determines Patterns of Nutrient Release by Stream Invertebrates. / Hood, James M.; McNeely, Camille; Finlay, Jacques C; Sterner, Robert W.

In: Freshwater Science, Vol. 33, No. 4, 01.01.2014, p. 1093-1107.

Research output: Contribution to journalArticle

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