2020
Ishikawa, Naoto F.; Finlay, Jacques C.; Uno, Hiromi; Ogawa, Nanako O.; Ohkouchi, Naohiko; Tayasu, Ichiro; Power, Mary E.
Combined use of radiocarbon and stable carbon isotopes for the source mixing model in a stream food web Journal Article
In: Limnology and Oceanography, vol. 65, no. 11, pp. 2688-2696, 2020.
Abstract | Links | BibTeX | Tags: ERCZO, food web, freshwater ecosystem, stable isotopes, stream invertebrates
@article{Ishikawa2020,
title = {Combined use of radiocarbon and stable carbon isotopes for the source mixing model in a stream food web},
author = {Naoto F. Ishikawa and Jacques C. Finlay and Hiromi Uno and Nanako O. Ogawa and Naohiko Ohkouchi and Ichiro Tayasu and Mary E. Power},
doi = {10.1002/lno.11541},
year = {2020},
date = {2020-07-06},
journal = {Limnology and Oceanography},
volume = {65},
number = {11},
pages = {2688-2696},
abstract = {Radiocarbon natural abundance (Δ14C) has emerged as a useful dietary tracer in freshwater ecology for the past decade, yet its applicability for separating aquatic and terrestrial resources has not been examined quantitatively. Here, we report Δ14C values of stream invertebrates in different functional feeding groups collected from the upper South Fork Eel River watershed, northern California. We found that algae‐grazing insect larvae show low Δ14C values (−43.1 ± 21.8‰, mean ± standard deviation},
keywords = {ERCZO, food web, freshwater ecosystem, stable isotopes, stream invertebrates},
pubstate = {published},
tppubtype = {article}
}
Radiocarbon natural abundance (Δ14C) has emerged as a useful dietary tracer in freshwater ecology for the past decade, yet its applicability for separating aquatic and terrestrial resources has not been examined quantitatively. Here, we report Δ14C values of stream invertebrates in different functional feeding groups collected from the upper South Fork Eel River watershed, northern California. We found that algae‐grazing insect larvae show low Δ14C values (−43.1 ± 21.8‰, mean ± standard deviation
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.