Trophic guilds of generalist feeders in soil animal communities as indicated by stable isotope analysis (15N/14N)

AbstractWe investigated if the commonly used aggregation of organisms into trophic guilds, such as detritivores and predators, in fact represent distinct trophic levels. Soil arthropods of a forest-meadow transect were ascribed a priori to trophic guilds (herbivores, detritivores, predators and necrovores), which are often used as an equivalent to trophic levels. We analysed natural variations in 15N/14N ratios of the animals in order to investigate the trophic similarity of organisms within (a priori defined) trophic guilds. Using trophic guilds as an equivalent to trophic level, the assumed stepwise enrichment of 15N by 3.4‰ per trophic level did not apply to detritivores; they were only enriched in 15N by on average 1.5‰ compared to litter materials. Predators on average were enriched in 15N by 3.5‰ compared to detritivores. Within detritvores and predators δ15N signatures varied markedly, indicating that these trophic guilds are dominated by generalist feeders which form a gradient of organisms feeding on different resources. The results indicate that commonly used trophic guilds, in particular detritivores and predators, do not represent trophic levels but consist of subguilds, i.e. subsets of organisms differing in resource utilization. In particular, in soil and litter food webs where trophic level omnivory is common, the use of distinct trophic levels may be inappropriate. Guilds of species delineated by natural variations of stable isotope ratios are assumed to more adequately represent the structure of litter and soil food webs allowing a more detailed understanding of their functioning.

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Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs

Diversity ◽

10.3390/d11090163 ◽

2019 ◽

Vol 11 (9) ◽

pp. 163 ◽

Cited By ~ 1

Author(s):

Hong ◽

Wiley ◽

Powers ◽

Michener ◽

Kaufman ◽

...

Keyword(s):

Stable Isotope ◽

Food Web ◽

Food Webs ◽

Trophic Level ◽

Isotope Analysis ◽

Diet Shift ◽

Turnover Rates ◽

Δ13c And Δ15n ◽

Isotopic Signatures ◽

Over Time

The great shearwater (Ardenna gravis) is a common pelagic bird with a distribution that spans almost the entire Atlantic basin, which in conjunction with its relatively high abundance, makes great shearwaters an effective bio indicator. We compared δ13C and δ15N values from the feathers, red blood cells (RBCs), and plasma of great shearwaters collected in 2014 and 2015 from the waters off Massachusetts and Cape Cod. The δ13C and δ15N values of RBCs were quite constant between sampling periods and years, suggesting a generally stable food web over that time period. However, the δ13C of plasma indicates a small seasonal change in diet between July and September for both years, with plasma δ15N values suggesting a slight increase in trophic level late in summer. Comparison of the δ15N of RBCs and plasma indicates that great shearwaters experienced a diet shift during the first few weeks of summer 2014, but not in 2015. Comparisons with other studies suggest that these shearwaters feed at a lower trophic level than great shearwaters sampled in the Bay of Fundy and that there is a decrease in δ13C with increasing latitude, which could indicate a more pelagic diet in northern waters. Stable isotope analysis of the sixth primary feathers provided evidence that these feathers are molted in the Northern Hemisphere and that the diet of great shearwaters shortly after arrival was different in 2014 and 2015. This study demonstrates that within species comparisons of tissue isotopic signatures over time and comparisons of isotopic signatures of tissues with different turnover rates, can detect changes in diet and be used as a tool to monitor for changes in marine food webs over time and space. The relevant signals remain informative even in the absence of species-specific data on tissue-diet discrimination factors, tissue turnover rates, or knowledge of dietary components and their stable isotopic signatures, suggesting dietary changes indicative of a corresponding change in the food web.

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Young, Old, and Weathered Carbon—Part 2: Using Radiocarbon and Stable Isotopes to Identify Terrestrial Carbon Support of the Food Web in an Alkaline, Humic Lake

Radiocarbon ◽

10.2458/azu_rc.57.18355 ◽

2015 ◽

Vol 57 (3) ◽

pp. 425-438 ◽

Cited By ~ 15

Author(s):

Evelyn M Keaveney ◽

Paula J Reimer ◽

Robert H Foy

Keyword(s):

Stable Isotope ◽

Food Web ◽

Food Webs ◽

Isotope Analysis ◽

Carbon Sources ◽

Carbon Support ◽

Trophic Levels ◽

Terrestrial Carbon ◽

Organic C ◽

Fish Samples

Carbon (C) and nitrogen (N) stable isotope analysis (SIA) has been used to identify the terrestrial subsidy of freshwater food webs. However, SIA fails to differentiate between the contributions of old and recently fixed terrestrial C and consequently cannot fully determine the source, age, and biochemical quality of terrestrial carbon. Natural abundance radiocarbon (Δ14C) was used to examine the age and origin of carbon in Lower Lough Erne, Northern Ireland. 14C and stable isotope values were obtained from invertebrate, algae, and fish samples, and the results indicate that terrestrial organic C is evident at all trophic levels. High winter δ15N values in calanoid zooplankton (δ15N = 24‰) relative to phytoplankton and particulate organic matter (δ15N = 6‰ and 12‰, respectively) may reflect several microbial trophic levels between terrestrial C and calanoid invertebrates. Winter and summer calanoid Δ14C values show a seasonal switch between autochthonous and terrestrial carbon sources. Fish Δ14C values indicate terrestrial support at the highest trophic levels in littoral and pelagic food webs. 14C therefore is useful in attributing the source of carbon in freshwater in addition to tracing the pathway of terrestrial carbon through the food web.

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Food-web modification in the eastern Gulf of Finland after invasion of Marenzelleria arctia (Spionidae, Polychaeta)

NeoBiota ◽

10.3897/neobiota.66.63847 ◽

2021 ◽

Vol 66 ◽

pp. 75-94

Author(s):

Sergey Golubkov ◽

Alexei Tiunov ◽

Mikhail Golubkov

Keyword(s):

Food Web ◽

Food Webs ◽

Food Chain ◽

Native Species ◽

Isotope Analysis ◽

Marine Species ◽

Trophic Levels ◽

Benthivorous Fish ◽

Neva Estuary ◽

The Baltic

The paucity of data on non-indigenous marine species is a particular challenge for understanding the ecology of invasions and prioritising conservation and research efforts in marine ecosystems. Marenzelleria spp. are amongst the most successful non-native benthic species in the Baltic Sea during recent decades. We used stable isotope analysis (SIA) to test the hypothesis that the dominance of polychaete worm Marenzelleria arctia in the zoobenthos of the Neva Estuary after its invasion in the late 2000s is related to the position of this species in the benthic food webs. The trend towards a gradual decrease in the biomass of Marenzelleria worms was observed during 2014–2020, probably due to significant negative relationships between the biomass of oligochaetes and polychaetes, both of which, according to SIA, primarily use allochthonous organic carbon for their production. The biomass of benthic crustaceans practically did not change and remained very low. The SIA showed that, in contrast to the native crustacean Monoporeia affinis, polychates are practically not consumed either by the main invertebrate predator Saduria entomon, which preys on M. affinis, oligochaetes and larvae of chironomids or by benthivorous fish that prefer native benthic crustaceans. A hypothetical model for the position and functional role of M. arctia in the bottom food web is presented and discussed. According the model, the invasion of M. arctia has created an offshoot food chain in the Estuary food webs. The former dominant food webs, associated with native crustaceans, are now poorly developed. The lack of top-down control obviously contributes to the significant development of the Marenzelleria food chain, which, unlike native food chains, does not provide energy transfer from autochthonous and allochthonous organic matter to the upper trophic levels. The study showed that an alien species, without displacing native species, can significantly change the structure of food webs, creating blind offshoots of the food chain.

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Current methods and future directions in avian diet analysis

The Auk ◽

10.1093/ornithology/ukab077 ◽

2021 ◽

Cited By ~ 1

Author(s):

Brandon D Hoenig ◽

Allison M Snider ◽

Anna M Forsman ◽

Keith A Hobson ◽

Steven C Latta ◽

...

Keyword(s):

Stable Isotope ◽

Food Webs ◽

Stable Isotope Analysis ◽

Dietary Habits ◽

Isotope Analysis ◽

Diet Analysis ◽

Unified Framework ◽

Future Directions ◽

Laboratory Techniques ◽

Prey Identification

Abstract Identifying the composition of avian diets is a critical step in characterizing the roles of birds within ecosystems. However, because birds are a diverse taxonomic group with equally diverse dietary habits, gaining an accurate and thorough understanding of avian diet can be difficult. In addition to overcoming the inherent difficulties of studying birds, the field is advancing rapidly, and researchers are challenged with a myriad of methods to study avian diet, a task that has only become more difficult with the introduction of laboratory techniques to dietary studies. Because methodology drives inference, it is important that researchers are aware of the capabilities and limitations of each method to ensure the results of their study are interpreted correctly. However, few reviews exist which detail each of the traditional and laboratory techniques used in dietary studies, with even fewer framing these methods through a bird-specific lens. Here, we discuss the strengths and limitations of morphological prey identification, DNA-based techniques, stable isotope analysis, and the tracing of dietary biomolecules throughout food webs. We identify areas of improvement for each method, provide instances in which the combination of techniques can yield the most comprehensive findings, introduce potential avenues for combining results from each technique within a unified framework, and present recommendations for the future focus of avian dietary research.

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Morphology and stable isotope analysis demonstrate different structuring of bat communities in rainforest and savannah habitats

Royal Society Open Science ◽

10.1098/rsos.180849 ◽

2018 ◽

Vol 5 (12) ◽

pp. 180849 ◽

Cited By ~ 1

Author(s):

Ara Monadjem ◽

Adam Kane ◽

Peter Taylor ◽

Leigh R. Richards ◽

Grant Hall ◽

...

Keyword(s):

Stable Isotope ◽

Stable Isotope Analysis ◽

Niche Breadth ◽

Isotope Analysis ◽

Morphological Characters ◽

Trophic Levels ◽

Species Packing ◽

Dietary Niche ◽

The One ◽

Ellipse Area

Bats play important ecological roles in tropical systems, yet how these communities are structured is still poorly understood. Our study explores the structure of African bat communities using morphological characters to define the morphospace occupied by these bats and stable isotope analysis to define their dietary niche breadth. We compared two communities, one in rainforest (Liberia) and one in savannah (South Africa), and asked whether the greater richness in the rainforest was due to more species ‘packing’ into the same morphospace and trophic space than bats from the savannah, or some other arrangement. In the rainforest, bats occupied a larger area in morphospace and species packing was higher than in the savannah; although this difference disappeared when comparing insectivorous bats only. There were also differences in morphospace occupied by different foraging groups (aerial, edge, clutter and fruitbat). Stable isotope analysis revealed that the range of δ 13 C values was almost double in rainforest than in savannah indicating a greater range of utilization of basal C 3 and C 4 resources in the former site, covering primary productivity from both these sources. The ranges in δ 15 N, however, were similar between the two habitats suggesting a similar number of trophic levels. Niche breadth, as defined by either standard ellipse area or convex hull, was greater for the bat community in rainforest than in savannah, with all four foraging groups having larger niche breadths in the former than the latter. The higher inter-species morphospace and niche breadth in forest bats suggest that species packing is not necessarily competitive. By employing morphometrics and stable isotope analysis, we have shown that the rainforest bat community packs more species in morphospace and uses a larger niche breadth than the one in savannah.

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Tackling the jelly web: Trophic ecology of gelatinous zooplankton in oceanic food webs of the eastern tropical Atlantic assessed by stable isotope analysis

Limnology and Oceanography ◽

10.1002/lno.11605 ◽

2020 ◽

Author(s):

Xupeng Chi ◽

Jan Dierking ◽

Henk‐Jan Hoving ◽

Florian Lüskow ◽

Anneke Denda ◽

...

Keyword(s):

Stable Isotope ◽

Food Webs ◽

Stable Isotope Analysis ◽

Trophic Ecology ◽

Isotope Analysis ◽

Gelatinous Zooplankton ◽

Tropical Atlantic ◽

Oceanic Food Webs

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Application of stable isotope analysis to differentiate shrimp extracted by industrial fishing or produced through aquaculture practices

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2014-0005 ◽

2014 ◽

Vol 71 (10) ◽

pp. 1520-1528 ◽

Cited By ~ 17

Author(s):

Julián Gamboa-Delgado ◽

César Molina-Poveda ◽

Daniel Enrique Godínez-Siordia ◽

David Villarreal-Cavazos ◽

Denis Ricque-Marie ◽

...

Keyword(s):

Stable Isotope ◽

Isotope Analysis ◽

Pacific White Shrimp ◽

Trophic Levels ◽

White Shrimp ◽

Nitrogen Stable Isotope ◽

Carbon And Nitrogen ◽

Open Sea ◽

Clear Differentiation ◽

Shrimp Farms

Carbon and nitrogen stable isotope values were determined in Pacific white shrimp (Litopenaeus vannamei) with the objective of discriminating animals produced through aquaculture practices from those extracted from the wild. Farmed animals were collected at semi-intensive shrimp farms in Mexico and Ecuador. Fisheries-derived shrimps were caught in different fishing areas representing two estuarine systems and four open sea locations in Mexico and Ecuador. Carbon and nitrogen stable isotope values (δ13CVPDB and δ15NAIR) allowed clear differentiation of wild from farmed animals. δ13CVPDB and δ15NAIR values in shrimps collected in the open sea were isotopically enriched (−16.99‰ and 11.57‰), indicating that these organisms belong to higher trophic levels than farmed animals. δ13CVPDB and δ15NAIR values of farmed animals (−19.72‰ and 7.85‰, respectively) partially overlapped with values measured in animals collected in estuaries (−18.46‰ and 5.38‰, respectively). Canonical discriminant analysis showed that when used separately and in conjunction, δ13CVPDB and δ15NAIR values were powerful discriminatory variables and demonstrate the viability of isotopic evaluations to distinguish wild-caught shrimps from aquaculture shrimps. Methodological improvements will define a verification tool to support shrimp traceability protocols.

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Stable isotope analysis of food webs in wetland areas of Lake Balaton, Hungary abb;5

Fundamental and Applied Limnology / Archiv für Hydrobiologie ◽

10.1127/archiv-hydrobiol/146/1999/117 ◽

1999 ◽

Vol 146 (1) ◽

pp. 117-128 ◽

Cited By ~ 2

Author(s):

István Tátrai ◽

Kálmán Mátyás ◽

János Korponai ◽

Gábor Paulovits ◽

Piroska Pomogyi ◽

...

Keyword(s):

Stable Isotope ◽

Food Webs ◽

Stable Isotope Analysis ◽

Isotope Analysis ◽

Lake Balaton

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Stable Isotope Food Web Analysis of a Large Subtropical Lake: Alternative Explanations for15N Enrichment of Pelagic vs. Littoral Fisheries

The Scientific World JOURNAL ◽

10.1100/tsw.2003.55 ◽

2003 ◽

Vol 3 ◽

pp. 613-622 ◽

Cited By ~ 5

Author(s):

Karl E. Havens ◽

Binhe Gu ◽

Brian Fry ◽

Carol Kendall

Keyword(s):

Stable Isotope ◽

Food Web ◽

Food Webs ◽

Trophic Level ◽

Stable Isotope Ratio ◽

Pelagic Zone ◽

Primary Producers ◽

Subtropical Lake ◽

Primary Consumers ◽

Habitat Enrichment

The food webs of littoral, pelagic, and littoral-pelagic ecotone (interface) regions of a large subtropical lake were investigated using stable isotope ratio methods, expanding the focus of a previous fish-only study to include other food web components such as primary producers and invertebrates. In these food webs, δ13C increased ~4o/oo and δ15N increased ~10o/oo from primary producers to fish. The δ15N of fish was ~9o/oo in the littoral zone, ~10 o/oo in the ecotone, and ~12o/oo in the pelagic zone. The cross-habitat enrichment in fish15N corresponded with both an increase in the size of fish and an increase in the δ15N of primary consumers (mollusks). Despite larger body size in the pelagic zone, fish in all three habitats appear to occur at the same average trophic level (TL = 4), assuming an enrichment factor of 3.4o/oo per trophic level, and normalizing to the δ15N of primary consumers.

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