Sources of stable isotope variation among stranded Western Atlantic dolphins (<i>Tursiops truncatus</i>) in North Carolina

MacAvoy, Stephen E.; Cortese, Nicole; Cybulski, Jonathan D.; Hohn, Aleta A.; Macko, Stephen A.

doi:10.1111/mms.12425

Cited by 5 publications

(5 citation statements)

References 28 publications

(74 reference statements)

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“…Sulphur isotopes can provide useful information on foraging prey source pathways [ 20 , 21 ], G. m. edwardii δ 34 S values from this study were similar to those reported in G. m. melas in the Mediterranean [ 102 ]. High δ 34 S (

21.52‰, n = 36) values indicated a large contribution to diet from marine sulphate, indicating marine foraging pathways [ 20 , 104 , 105 ]. The combination of low δ 13 C values with high δ 34 S values observed in this study has previously been described as typical of oceanic feeding behaviour [ 106 ], corroborating that G. melas is primarily an oceanic species [ 34 , 107 , 108 ].…”

Section: Discussionmentioning

confidence: 99%

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Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

Hinton

Stockin

Bury

et al. 2022

Biology

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The quantification of a species’ trophic niche is important to understand the species ecology and its interactions with the ecosystem it resides in. Despite the high frequency of long-finned pilot whale (Globicephala melas edwardii) strandings on the Aotearoa New Zealand coast, their trophic niche remains poorly understood. To assess the isotopic niche of G. m. edwardii within New Zealand, ontogenetic (sex, total body length, age, maturity status, reproductive group) and spatiotemporal (stranding location, stranding event, and stranding year) variation were investigated. Stable isotopes of carbon (δ13C) and nitrogen (δ15N) were examined from skin samples of 125 G. m. edwardii (67 females and 58 males) collected at mass-stranding events at Onetahua Farewell Spit in 2009 (n = 20), 2011 (n = 20), 2014 (n = 27) and 2017 (n = 20) and at Rakiura Stewart Island in 2010 (n = 19) and 2011 (n = 19). Variations in δ34S values were examined for a subset of 36 individuals. General additive models revealed that stranding event was the strongest predictor for δ13C and δ15N values, whilst sex was the strongest predictor of δ34S isotopic values. Although similar within years, δ13C values were lower in 2014 and 2017 compared to all other years. Furthermore, δ15N values were higher within Farewell Spit 2017 compared to any other stranding event. This suggests that the individuals stranded in Farewell Spit in 2017 may have been feeding at a higher trophic level, or that the nitrogen baseline may have been higher in 2017 than in other years. Spatiotemporal differences explained isotopic variation of G. m. edwardii in New Zealand waters better than ontogenetic factors.

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Section: Discussionmentioning

confidence: 99%

“…Hence, this study did not reveal a link between consumption of prey from higher trophic levels and body length. Similarly, no relationship was evident between stable isotope values and body length in P. macrocephalus [ 93 , 114 ], or δ 34 S, sex and body size in T. truncatus [ 104 ].…”

Section: Discussionmentioning

confidence: 99%

Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

Hinton

Stockin

Bury

et al. 2022

Biology

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“…For example, elevated δ 15 N values and corresponding high cortisol levels measured in blood from starving animals may indicate more extreme nutritional stress, whereas lower δ 15 N values and higher cortisol levels may indicate normal fasting conditions in a migratory capitol breeder. In the marine environment, stable oxygen (δ 18 O), or δ deuterium (δ 2 H) isotope values can provide additional gradients for tracking movements in the ocean, especially between coastal and offshore habitats, and polar and temperate latitudes (McMahon et al, 2013;MacAvoy et al, 2017). In polar regions, the inclusion of δ 2 H may correlate to sea ice concentration (deHart and Picco, 2015), offering opportunities to examine migration, sea ice conditions, and stress by combining stable isotope and hormone analyses.…”

Section: Life Historymentioning

confidence: 99%

The Utility of Combining Stable Isotope and Hormone Analyses for Marine Megafauna Research

et al. 2018

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Stable isotope and hormone analyses offer insight into the health, stress, nutrition, movements, and reproduction of individuals and populations. Such information can provide early warning signs or more in-depth details on the ecological and conservation status of marine megafauna. Stable isotope and hormone analyses have seen rapid development over the last two decades, and we briefly review established protocols and particular questions emphasized in the literature for each type of analysis in isolation. Little has been published utilizing both methods concurrently for marine megafauna yet there has been considerable effort on this front in seabird and terrestrial predator research fields. Using these other taxa as examples, we offer a few of the major research areas and questions we foresee as productive for the intersection of these two methods and discuss how they can inform marine megafauna conservation and management efforts. Three major research areas have utilized a combination of these two methods: (1) nutrition and health, (2) reproduction, and (3) life history. We identify a fourth area of research, examinations of evolutionary versus ecological drivers of behavior, that could also be well served by a combined stable isotope and hormone analyses approach. Each of these broad areas of research will require methodological developments. In particular, research is needed to enable the successful temporal alignment of these two analytical techniques.

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“…Some researchers lipid extract all tissues, regardless of the C:N ratio (e.g. Hooker, Iverson, Ostrom, & Smith, 2001; MacAvoy, Cortese, Cybulski, Hohn, & Macko, 2017; O'Donovan, Budge, Hobson, Kelly, & Derocher, 2018). However, blanket LEs can create unnecessary work and expense if LE is unnecessary or techniques alter nitrogen values, as is common in tissues containing many proteins and polar nitrogenous compounds (Logan et al, 2008; Logan & Lutcavage, 2008; Sweeting et al, 2006), forcing researchers to analyse each sample twice, once on lipid‐extracted tissues for carbon values and again on bulk tissues for nitrogen.…”

Section: Introductionmentioning

confidence: 99%

The effects of lipid extraction on δ¹³C and δ¹⁵N values and use of lipid‐correction models across tissues, taxa and trophic groups

et al. 2020

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1. Lipid-rich animal tissues have low δ 13 C values, which can lead to inaccurate ecological inferences. Chemical lipid extraction (LE) or correction models account for this depletion, but the need for LE or correction is tissue-and species-specific. Also, LE can alter δ 15 N values, increasing labour and costs because bulk samples must be analysed for δ 15 N values separately.2. We studied the effects of LE on δ 13 C and δ 15 N values in liver, muscle and skin of common bottlenose dolphins Tursiops truncatus and West Indian manatees Trichechus manatus, two ecologically important species that occupy different trophic levels. We fit lipid-correction models to each species. We also performed a meta-analysis to more broadly determine the effects of LE across taxa, tissues and trophic groups (carnivores, omnivores and herbivores) and to fit lipid-correction models to different taxonomic and trophic groups.3. Lipid extraction increased the δ 13 C values in dolphin tissues but had little effect on manatee tissues and no effect on the δ 15 N values in either species. A mass balance lipid-correction model best fit the data from all dolphin tissues, and a linear model best fit data for manatee liver while null models best fit data from manatee muscle and skin. Across 128 terrestrial and aquatic species, the effects of LE varied among tissues and were lower for herbivores compared to carnivores. The best-fitting lipid-correction models varied among tissue, taxa and trophic groups. Finally, the δ 15 N values from muscle and liver were affected by LE. 4.Our results strengthen the growing body of evidence that the need for LE is tissue-and species-specific, without a reliable C:N ratio predictive threshold.The prediction errors of lipid-correction models generally decreased with taxonomic and trophic specificity. The smaller effects of LE in herbivores may be due to differences in diet composition or the physiology of lipid synthesis in members of this trophic group. These results suggest that researchers should use the most species-, tissue-and trophic group-specific information on LE available and, if not available, perform LE on a subset of samples prior to analysis to determine effects.Additional supporting information may be found online in the Supporting Information section.How to cite this article: Cloyed CS, DaCosta KP, Hodanbosi MR, Carmichael RH. The effects of lipid extraction on δ 13 C and δ 15 N values and use of lipid-correction models across tissues, taxa and trophic groups. Methods Ecol Evol. 2020;11:751-762.

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Sources of stable isotope variation among stranded Western Atlantic dolphins (Tursiops truncatus) in North Carolina

Cited by 5 publications

References 28 publications

Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

The Utility of Combining Stable Isotope and Hormone Analyses for Marine Megafauna Research

The effects of lipid extraction on δ¹³C and δ¹⁵N values and use of lipid‐correction models across tissues, taxa and trophic groups

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Sources of stable isotope variation among stranded Western Atlantic dolphins (Tursiops truncatus) in North Carolina

Cited by 5 publications

References 28 publications

Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

The Utility of Combining Stable Isotope and Hormone Analyses for Marine Megafauna Research

The effects of lipid extraction on δ13C and δ15N values and use of lipid‐correction models across tissues, taxa and trophic groups

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Product

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The effects of lipid extraction on δ¹³C and δ¹⁵N values and use of lipid‐correction models across tissues, taxa and trophic groups