2014
Hood, James M.; McNeely, Camille; Finlay, Jacques C.; Sterner, Robert W.
Selective feeding determines patterns of nutrient release by stream invertebrates Journal Article
In: Freshwater Science, vol. 33, no. 4, pp. 1093-1107, 2014, ISSN: 2161-9549.
Abstract | Links | BibTeX | Tags: nutrients, selective feeding, stream invertebrates
@article{Hood2014,
title = {Selective feeding determines patterns of nutrient release by stream invertebrates},
author = {James M. Hood and Camille McNeely and Jacques C. Finlay and Robert W. Sterner},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Hood_2014_FreshSci.pdf},
doi = {10.1086/678693},
issn = {2161-9549},
year = {2014},
date = {2014-09-19},
journal = {Freshwater Science},
volume = {33},
number = {4},
pages = {1093-1107},
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.},
keywords = {nutrients, selective feeding, stream invertebrates},
pubstate = {published},
tppubtype = {article}
}
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.