Mapping trophic continua of benthic foodwebs:body size-δ15N relationships

France, Robert; Chandler, Margaret Ann; Peters, Robert H.

doi:10.3354/meps174301

Cited by 87 publications

(70 citation statements)

References 28 publications

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“…However, in all four wetlands, the gut contents of zygopterans showed that they consumed prey only at trophic level 3 (i.e., they ate only chironomid larvae and zooplankton at level 2). We readily accept the notion of noninteger trophic levels (Ulanowicz 1995; France et al 1998;Post et al 2000 Zanden et al 1999;Post et al 2000). Alternative explanations in our study and others should be considered.…”

Section: Interpreting ␦supporting

confidence: 69%

Interpreting stable isotopes from macroinvertebrate foodwebs in saline wetlands

Hart

Lovvorn

2002

Limnology & Oceanography

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We compared stable‐isotope (δ13C and δ15N) and gut‐content analyses of macroinvertebrate foodwebs in saline wetlands of the Laramie Basin, Wyoming, USA. Standard assumptions of stable‐isotope fractionation between trophic levels (<1‰ for δ13C, mean of 3.4‰ for δ15N) suggested that zygopteran (damselfly) larvae consumed mainly amphipods. However, the guts of zygopterans contained no amphipods but rather a mix of chironomid larvae and zooplankton. In all wetlands the gut contents of zygopterans indicated that they were secondary consumers (trophic level 3), but enrichment of δ15N between zygopterans and their prey (Δδ15N) varied from 1 to 3.4‰ between wetlands. In other studies, such variation in Δδ15N has been interpreted to mean that food‐chain length differed between aquatic systems. We review alternative interpretations of variable 15N enrichment, namely, varying C:N ratios in food, differential enrichment between consumer species, and habitat‐specific variation of δ15N at the base of foodwebs. We also suggest that variation in the timing and rates of nitrogen cycling can affect measured Δδ15N both within and between foodwebs. For aquatic macroinvertebrates, we urge that stable isotopes be supplemented with independent observations to avoid incorrect conclusions about trophic pathways, trophic levels, and food‐chain lengths in different ecosystems.

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Section: Interpreting ␦supporting

confidence: 69%

Interpreting stable isotopes from macroinvertebrate foodwebs in saline wetlands

Hart

Lovvorn

2002

Limnology & Oceanography

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“…Overall food web-The isotopic ranges observed in the St. Lawrence ETZ are similar to those in other estuarine ecosystems, with broad omnivory and an absence of distinct trophic levels (France et al 1998). The pronounced d 13 C offset between consumers and seston and the relatively small d 15 N difference relative to primary consumers of lowest trophic rank were previously reported by Martineau et al (2004).…”

Section: Discussionmentioning

confidence: 57%

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

et al. 2006

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We evaluated by stable isotope analysis the trophic structure of an estuarine transition zone (ETZ) food web and the role of an invasive species, the veliger stage of the zebra mussel Dreissena polymorpha. In the St. Lawrence ETZ, where zebra mussel veligers are now the dominant zooplankton in summer, d 13 C ranged from 231.2% (seston) to 216.1% (adult fish) and d 15 N ranged from 2.6% to 17.4%. Isotopic analysis of samples indicated that the overall food web was largely supported by autochthonous phytoplankton rather than by allochthonous terrestrial carbon. Large differences among the isotopic signals of veligers, cladocerans, and copepods suggested the use of different proportions of food items, and the isotopic values of fish larvae indicated no significant assimilation of veligers. The d 13 C signature of the veligers was in a range consistent with feeding on free-living bacteria and dissolved organic carbon (DOC) or both, and freshwater algae incubated in situ. To investigate the possibility of DOC uptake by the veligers, we incubated veligers on 14 C-labelled algal lysates. There was rapid uptake of DOC and incorporation into biomass, equivalent to 6% of the soft tissue dry weight per hour. Zebra mussel veligers are likely using autochthonous DOC as an alternate food source, and they occupy an exotic trophic position in which there is little direct interaction with other major components of the ETZ food web.

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“…This implies that heavier size-classes are higher in the trophic continuum, a pattern demonstrated empirically for plankton (Fry & Quinones 1994), benthic invertebrate (France et al 1998) and fish (Jennings et al 2002) communities. The trophic continua across body sizeclasses also show that fixed (integer) trophic levels do not appropriately describe the structure of aquatic food webs, and trophic level can thus refer to any point on the continuum.…”

Section: Introductionmentioning

confidence: 66%

“…Indeed, Fry & Quinones (1994), France et al (1998) and Jennings et al (2002) have already used nitrogen stable isotope analysis to show that the trophic levels of plankton, invertebrates and fishes in biomass size-spectra increase continuously with increasing body size. Nitrogen stable isotope analysis is preferable to diet analysis for estimating trophic levels in many marine food webs because most species switch their diet frequently, prey on species that are digested at different rates, have gut contents that cannot be identified, or regurgitate gut contents on capture (Staniland et al 2001.…”

Section: Introductionmentioning

confidence: 99%

Use of size-based production and stable isotope analyses to predict trophic transfer efficiencies and predator-prey body mass ratios in food webs

Jennings¹,

Warr²,

Mackinson³

2002

Mar. Ecol. Prog. Ser.

200

180

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Methods of assessing the structure and function of food webs are needed to provide a basis for assessing large-scale direct (e.g. fisheries) and indirect (e.g. climate change) effects of human activities on marine ecosystems. We present a simple synthesis of the complex structure and function of a real marine food web, based on analyses of body size distributions, production-body size relationships and trophic level-body size relationships. We show how size-based estimates of production, species richness and trophic level (from nitrogen stable isotope analysis) can be used to quantify trophic transfer efficiency, mean predator-prey body-mass ratios and the mean ratio of the number of predator to prey species in marine food webs. We applied these methods to the central North Sea, and estimated transfer efficiencies of 3.7 to 12.4%, a mean predator-prey body-mass ratio of 109:1 and a mean ratio of the number of predator to prey species of 0.34. We conducted sensitivity analyses to show how differences in the fractionation of δ 15 N and changes in the slope of the relationship between production and δ 15 N affected our predictions. Our estimates of transfer efficiency and mean predator-prey body-mass ratios are similar to those obtained by costly and labour-intensive diet-and ecosystem-modelling studies. Coupled analyses of size and trophic structure may provide a method for validating ecosystem models and assessing human impacts on marine ecosystems. KEY WORDS: Body size · Food web · Transfer efficiency · Stable isotope analysis · Production · DiversityResale or republication not permitted without written consent of the publisher

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Mapping trophic continua of benthic foodwebs:body size-δ15N relationships

Cited by 87 publications

References 28 publications

Interpreting stable isotopes from macroinvertebrate foodwebs in saline wetlands

Interpreting stable isotopes from macroinvertebrate foodwebs in saline wetlands

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

Use of size-based production and stable isotope analyses to predict trophic transfer efficiencies and predator-prey body mass ratios in food webs

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