Skip to Main Content
Food resources of stream macroinvertebrates determined by natural-abundance stable C and N isotopes and a 15N tracer additionAuthor(s): Patrick J. Mulholland; Jennifer L. Tank; Diane M. Sanzone; Wilfrid M. Wollheim; Bruce J. Peterson; Jackson R. Webster; Judy L. Meyer
Source: Journal of the North American Benthol Society, 2000, 19(1): 145-157
Publication Series: Miscellaneous Publication
PDF: View PDF (951 KB)
DescriptionTrophic relationships were examined using natural-abundance 13C and 15N analyses and a 15N-tracer addition experiment in Walker Branch, a 1st-order forested stream in eastern Tennessee. In the 15N-tracer addition experiment, we added 15NH4, to stream water over a 6-wk period In early spring, and measured 15N:14N ratios in different taxa and biomass compartments over distance and time. Samples collected from a station upstream from the 15N addition provided data on natural-abundance 13C:12C and 15N:14N ratios. The natural-abundance 15N analysis proved to be of limited value in identifying food resources of macroinvertebrates because 15N values were not greatly different among food resources. In general, the natural-abundance stable isotope approach was most useful for determining whether epilithon or detritus were important food resources for organisms that may use both (e.g., the snail Elimia clavaeformis), and to provide corroborative evidence of food resources of taxa for which the 15N tracer results were not definitive. The 15N tracer results showed that the mayflies Stenonema spp. and Baetis spp. assimilated primarily epilithon, although Baetis appeared to assimilate a portion of the epilithon (e.g., algal cells) with more rapid N turnover than the bulk pool sampled. Although Elimia did not reach isotopic equilibrium during the tracer experiment, application of a N-turnover model to the field data suggested that it assimilated a combination of epilithon and detritus. The amphipod Gammarus minus appeared to depend mostly on fine benthic organic matter (FBOM), and the coleopteran Anchytarsus bicolor on epixylon. The caddisfly Diplectrona modesta appeared to assimilate primarily a fast N-turnover portion of the FBOM pool, and Simuliidae a fast N- turnover component of the suspended particulate organic matter pool rather than the bulk pool sampled. Together, the natural-abundance stable C and N isotope analyses and the experimental 15N tracer approach proved to be very useful tools for identifying food resources in this stream ecosystem.
- You may send email to email@example.com to request a hard copy of this publication.
- (Please specify exactly which publication you are requesting and your mailing address.)
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationMulholland, Patrick J.; Tank, Jennifer L.; Sanzone, Diane M.; Wollheim, Wilfrid M.; Peterson, Bruce J.; Webster, Jackson R.; Meyer, Judy L. 2000. Food resources of stream macroinvertebrates determined by natural-abundance stable C and N isotopes and a 15N tracer addition. Journal of the North American Benthol Society, 2000, 19(1): 145-157
KeywordsStream macroinvertebrates, food resources, N cycling, tracer addition, stable isotope, 15N, 13C
- You are not always what we think you eat: selective assimilation across multiple whole-stream isotopic tracer studies
- Fungal functioning in a pine forest: evidence from a 15N-labeled global change experiment
- Microbial incorporation of nitrogen in stream detritus
XML: View XML