scholarly journals Isotopic niche reflects stress-induced variability in physiological status

2018 ◽  
Vol 5 (2) ◽  
pp. 171398 ◽  
Author(s):  
Agnes M. L. Karlson ◽  
Martin Reutgard ◽  
Andrius Garbaras ◽  
Elena Gorokhova
Keyword(s):  
Body Size ◽  
Stable Isotope ◽  
Trophic Ecology ◽  
Physiological Stress ◽  
Isotope Composition ◽  
Stress Factors ◽  
Physiological Status ◽  
Isotopic Niche ◽  
Control Groups ◽  
Oxygen Conditions

The isotopic niche has become an established concept in trophic ecology. However, the assumptions behind this approach have rarely been evaluated. Evidence is accumulating that physiological stress can affect both magnitude and inter-individual variability of the isotopic signature in consumers via alterations in metabolic pathways. We hypothesized that stress factors (inadequate nutrition, parasite infestations, and exposure to toxic substances or varying oxygen conditions) might lead to suboptimal physiological performance and altered stable isotope signatures. The latter can be misinterpreted as alterations in isotopic niche. This hypothesis was tested by inducing physiological stress in the deposit-feeding amphipod Monoporeia affinis exposed to either different feeding regimes or contaminated sediments. In the amphipods, we measured body condition indices or reproductive output to assess growth status and δ 13 C and δ 15 N values to derive isotope niche metrics. As hypothesized, greater isotopic niche estimates were derived for the stressed animals compared to the control groups. Moreover, the δ 15 N values were influenced by body size, reproductive status and parasite infestations, while δ 13 C values were influenced by body size, oxygen conditions and survival. Using regression analysis with isotope composition and growth variables as predictors, we were able to discriminate between the amphipods exposed to nutritionally or chemically stressful conditions and those in the control groups. Thus, interpretation of isotopic niche can be confounded by natural or anthropogenic stressors that may induce an apparent change in isotopic niche. These findings stress the importance of including measures of growth and health status when evaluating stable isotope data in food web studies.

scholarly journals Body size and stable isotope composition of zooplankton in the western tropical Atlantic

2020 ◽  
Vol 212 ◽  
pp. 103449
Author(s):  
Gabriela Guerra Araújo Abrantes de Figueiredo ◽  
Ralf Schwamborn ◽  
Arnaud Bertrand ◽  
Jean-Marie Munaron ◽  
François Le Loc'h
Keyword(s):  
Body Size ◽  
Stable Isotope ◽  
Isotope Composition ◽  
Tropical Atlantic ◽  
Stable Isotope Composition

scholarly journals The influence of sex, hormone status, and growth rate on dietary isotope fractionation: a case study with laboratory rats

2021 ◽  
Author(s):  
Jessica Santollo ◽  
Caroline Jones ◽  
Sora L Kim
Keyword(s):  
Growth Rate ◽  
Stable Isotope ◽  
Stable Isotope Analysis ◽  
Trophic Ecology ◽  
Isotope Composition ◽  
Isotope Analysis ◽  
Gonadal Hormones ◽  
Gonadal Hormone ◽  
Laboratory Rats

Stable isotope analysis is increasingly used to discern ecological differences within and among species, especially those difficult to observe. In applied ecological studies, variations in stable isotope composition are often attributed to foraging behavior or trophic ecology rather than fractionation during metabolic processes. One physiological difference among individuals is gonadal hormone levels, which affects food intake, metabolism, and locomotor activity. However, it is unclear how these effects, isolated from ecology, affect metabolic dynamics and expression in stable isotope analysis. Here, we test the linkage between gonadal hormones and isotopic heterogeneity among individuals with captive rats. We found that sex and removal of gonadal hormones are factors either individually or interactive for d15N and d13C values in serum and blood as well as d15N values of muscle and liver. Furthermore, the degree of fractionation in these tissues is related to growth rate. Gonadectomization also affected isotopic composition for liver d13C values and kidney d15N values, but fat d13C values were affected only by sex. The pattern of differentiation between groups was most different for kidney d15N and d13C values, which also had the largest isotopic variability among groups. Overall, isotopic variation within one tissue for the four groups demonstrated up to 1 ‰ difference in d13C and d15N values suggesting that sex based within population variations should into consideration these potential physiological effects.

scholarly journals Trophic ecology of the seagrass-inhabiting footballer demoiselle Chrysiptera annulata (Peters, 1855); comparison with three other reef-associated damselfishes

2020 ◽  
Vol 146 (1) ◽  
Author(s):  
Gilles Lepoint ◽  
Loïc N. Michel ◽  
Eric Parmentier ◽  
Bruno Frédérich
Keyword(s):  
Stable Isotope ◽  
Trophic Ecology ◽  
Close Association ◽  
Isotope Analysis ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Isotopic Niche ◽  
Seagrass Meadows ◽  
Turf Algae ◽  
Herbivorous Species

Many damselfishes (Pomacentridae) are herbivorous or omnivorous with an important contribution from different kinds of algae in their diet. They display different levels of territoriality and farming behavior, from almost non territorial to monoculture farmers. In addition, a few species inhabit seagrass meadows but, presently, none can be considered as seagrass-eating specialists. The footballer demoiselle, Chrysiptera annulata, is found in the seagrass meadows on the reef flat of the Great Reef of Toliara (Madagascar, Mozambique Channel). In the light of this unusual habitat for a pomacentrid, this study aimed to answer three questions: 1) What is the diet of C. annulata? 2) Do the resources supporting this diet include seagrass? 3) Does its trophic niche overlap those of other sympatric damselfishes (Pomacentrus trilineatus, Chrysiptera unimaculata and Plectroglyphidodon lacrymatus) living in close association with macrophytes or eating algae? Stomach content examination and stable isotope analysis showed that the footballer demoiselle is not a seagrass consumer but is an omnivorous/herbivorous species heavily relying on algal resources and small invertebrates. SIAR, a stable isotope mixing model, indicated it assimilated large amounts of turf algae, and various benthic or planktonic invertebrates in lower proportions. SIBER metrics revealed that the isotopic niche of the footballer demoiselle partly overlaps that of its congener, C. unimaculata, but not those of P. trilineatus and P. lacrymatus. Trophic strategies of C. annulata differed both from farming species such as P. lacrymatus and from less territorial herbivores such as P. trilineatus. Its seagrass meadow habitat on the Great Reef of Toliara allows the conquest of an unusual habitat for damselfishes and could limit competition with C. unimaculata, a species displaying the same territorial behavior and the same isotopic niche but living on the reef itself.

Seasonal differences in foraging and isotopic niche width related to body size in Gulf of Alaska harbor seals

2019 ◽  
Vol 97 (12) ◽  
pp. 1156-1163 ◽  
Author(s):  
Justin Smith ◽  
Shawna Karpovich ◽  
Lara Horstmann ◽  
Julie McIntyre ◽  
Diane M. O’Brien
Keyword(s):  
Body Size ◽  
Stable Isotope ◽  
Isotope Analysis ◽  
Isotope Ratios ◽  
Gulf Of Alaska ◽  
Harbor Seal ◽  
Foraging Strategies ◽  
Stable Isotope Ratios ◽  
Isotopic Niche ◽  
Harbor Seals

Harbor seals (Phoca vitulina Linnaeus, 1758) use different foraging strategies based on body size and sex, but this difference can be difficult to evaluate across seasons. We used stable isotope analysis of harbor seal whiskers from 32 individuals to assess seasonal foraging of seals inhabiting tidewater glacial habitat in Southeast Alaska. We analyzed stable isotope ratios from serial sections of whiskers, estimated deposition date for each section, and used mixed models to determine if sex and body size influence stable isotope ratios. Seals were grouped by size (>1.4 m or ≤1.4 m curvilinear length) as a proxy for sexual maturity to describe isotopic differences between groups using standard ellipse corrected area. Mean carbon and nitrogen isotope ratios differed significantly between size classes (p < 0.005), with no effect of sex. Larger seals exhibited a broader isotopic niche in the fall, winter, and spring relative to smaller seals, but not in the summer. Our results suggest that seals using tidewater glacial habitat share common foraging behavior in the summer, while larger seals exhibit more diverse foraging throughout the rest of the year. These results highlight the importance of tidewater glacial habitat for this population of harbor seals during the summer.

scholarly journals Stable Isotope Analysis of Juvenile White Sharks Inside a Nursery Area Reveals Foraging in Demersal-Inshore Habitats and Trophic Overlap With Sympatric Sharks

2021 ◽  
Vol 8 ◽  
Author(s):  
Emiliano García-Rodríguez ◽  
Sharon Z. Herzka ◽  
Oscar Sosa-Nishizaki ◽  
Christopher G. Lowe ◽  
John B. O’Sullivan
Keyword(s):  
Stable Isotope ◽  
Early Life ◽  
Trophic Ecology ◽  
Trophic Position ◽  
Life Stage ◽  
Isotope Ratios ◽  
Nursery Area ◽  
Isotopic Niche ◽  
Life Stages ◽  
Early Life Stages

Knowledge about top predators’ trophic ecology is crucial for defining their role in ecosystems, understanding habitat preferences, characterizing life stage-specific feeding habits, and evaluating their interaction with fisheries. In the northeastern Pacific, white sharks (Carcharodon carcharias) occupy coastal habitats during the early life stages, including Bahía Sebastián Vizcaíno (BSV) in Mexico, which is a known nursery area. Although BSV presumably provides high prey abundance, the trophic ecology of immature white sharks is poorly understood. Carbon and nitrogen bulk stable isotope analyses (SIA) were used to explore the trophic relationship of early life stages with their potential prey and to infer dietary overlap with sympatric sharks, while SIA of amino acids were used to estimate trophic position. Muscle samples from young white sharks and inshore demersal prey commonly found in their stomach contents were sampled. Demersal prey and literature-derived isotope ratios for pelagic and offshore species were incorporated into mixing models with a Bayesian framework to estimate their contribution to white shark tissues. Nearshore demersal prey had the highest contribution for all life stages (between 35 and 47%), consistent with previous reports based on gut content analysis. The contribution of pelagic (between 26 and 37%) and offshore (between 14 and 32%) prey was smaller and suggests potential periodic changes in foraging grounds and the presence of a maternal-derived isotopic signature. A high contribution of demersal prey indicates a high level of interaction with local fisheries that target those species and catch white sharks incidentally and is consistent with immature shark movement patterns. Isotope ratios of two sympatric sharks, smooth hammerhead Sphyrna zygaena and copper sharks Carcharhinus brachyurus, were used to estimate the overlap in isotopic niche space. Immature white sharks had the smallest isotopic niche, while the highest was for copper sharks. Overlap was greatest between white sharks and hammerheads (∼45%), while overlap with copper sharks was limited (&lt;20%), suggesting less potential for competition. Trophic position estimates were similar to those previously reported for the species. These results highlight the importance of coastal demersal prey heavily targeted by local fisheries for the diet of young white sharks and support the importance of BSV as a nursery habitat.

scholarly journals The isotopic niche of Atlantic, biting marine mammals and its relationship to skull morphology and body size

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Massimiliano Drago ◽  
Marco Signaroli ◽  
Meica Valdivia ◽  
Enrique M. González ◽  
Asunción Borrell ◽  
...  
Keyword(s):  
Body Size ◽  
Atlantic Ocean ◽  
Fisheries Management ◽  
Marine Mammals ◽  
Trophic Position ◽  
Sympatric Species ◽  
Isotopic Niche ◽  
Apex Predators ◽  
Skull Morphology ◽  
Ecosystem Based Fisheries Management

AbstractUnderstanding the trophic niches of marine apex predators is necessary to understand interactions between species and to achieve sustainable, ecosystem-based fisheries management. Here, we review the stable carbon and nitrogen isotope ratios for biting marine mammals inhabiting the Atlantic Ocean to test the hypothesis that the relative position of each species within the isospace is rather invariant and that common and predictable patterns of resource partitioning exists because of constrains imposed by body size and skull morphology. Furthermore, we analyze in detail two species-rich communities to test the hypotheses that marine mammals are gape limited and that trophic position increases with gape size. The isotopic niches of species were highly consistent across regions and the topology of the community within the isospace was well conserved across the Atlantic Ocean. Furthermore, pinnipeds exhibited a much lower diversity of isotopic niches than odontocetes. Results also revealed body size as a poor predictor of the isotopic niche, a modest role of skull morphology in determining it, no evidence of gape limitation and little overlap in the isotopic niche of sympatric species. The overall evidence suggests limited trophic flexibility for most species and low ecological redundancy, which should be considered for ecosystem-based fisheries management.

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