Global review and inventory: how stable isotopes are helping us understand ecology and inform conservation of marine turtles

Haywood, Julia C.; Fuller, Wayne J.; Godley, Brendan J.; Shutler, Jamie D.; Widdicombe, Stephen; Broderick, Annette C.

doi:10.3354/meps12889

Cited by 39 publications

(36 citation statements)

References 224 publications

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“…This study adds to the growing body of literature that demonstrates the benefits of combining the complementary methodological approaches of satellite telemetry and SIA in understanding the spatial ecology of animal populations (e.g., Ceriani, Roth, Evans, Weishampel, & Ehrhart, ; Seminoff et al, ; Reich et al, ; for a review and references therein see Haywood et al, ). This combined approach allowed us to understand the importance of foraging grounds for the broader population, which demonstrates a remarkable difference from results obtained from several individuals using satellite telemetry alone.…”

Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 96%

“…Due to limited tissue quantity, six Alagadi individuals could only be run for δ 13 C and δ 15 N analysis, while 15 were analysed for all three stable isotope ratios (see Appendix ). δ 13 C and δ 15 N analysis were prioritized for comparison to previous SIA research, as only four marine turtle studies to date have analysed δ 34 S values (see review by Haywood et al, ). From the previous study only δ 13 C and δ 15 N values were available from Zakynthos individuals.…”

Section: Methodsmentioning

confidence: 99%

“…δ 13 C and δ 15 N analysis were prioritized for comparison to previous SIA research, as only four marine turtle studies to date have analysed δ 34 S values (see review by Haywood et al, 2019). From the previous study only δ 13 C and δ 15 N values were available from Zakynthos individuals.…”

Section: Foraging Ground Assignmentmentioning

confidence: 99%

“…This can provide fine-scale near real-time movement data on location and speed, but is an expensive technique, and this cost can often limit the sample size (Godley et al, 2008). In contrast, stable isotope analysis (SIA) is a powerful but relatively cheap forensic tool and has been used for several marine taxa (Bird et al, 2018;Newsome, Clementz, & Koch, 2010;Rubenstein & Hobson, 2004), including marine turtles (Figgener, Bernardo, & Plotkin, 2019a, 2019bHaywood et al, 2019), to gain insights into the spatial and foraging ecology of marine species. Combining the locational data of satellite telemetry with stable isotope ratios allows scaling up and has been shown to enable inference of habitat use at a population level (e.g., Bradshaw et al, 2017;Ceriani et al, 2015;Ceriani, Weishampel, Ehrhart, Mansfield, & Wunder, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Spatial ecology of loggerhead turtles: Insights from stable isotope markers and satellite telemetry

Haywood

Fuller

Godley

et al. 2020

Diversity and Distributions

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Aim Using a combination of satellite telemetry and stable isotope analysis (SIA), our aim was to identify foraging grounds of loggerhead turtles (Caretta caretta) at important rookeries in the Mediterranean, examine foraging ground fidelity, and across 25 years determine the proportion of nesting females recruiting from each foraging region to a major rookery in Cyprus. Location Mediterranean Sea. Methods Between 1993 and 2018, we investigated the spatial ecology of loggerhead turtles from rookeries in Cyprus and Greece using satellite telemetry (n = 55 adults) and SIA of three elements (n = 296). Results Satellite telemetry from both rookeries revealed the main foraging areas as the Adriatic region (Cyprus: 4% of individuals, Greece: 55%), Tunisian Plateau (Cyprus: 16%, Greece: 40%) and the eastern Mediterranean (Cyprus: 80%, Greece: 5%). Combining satellite telemetry and SIA allowed 64% of all nesting females to be assigned to; the Adriatic region (Cyprus: 2%, Greece: 38.5%), Tunisian Plateau (Cyprus: 47%, Greece: 38.5%) and the eastern Mediterranean (Cyprus: 51%, Greece: 23%), which are markedly different to proportions obtained using satellite telemetry. The proportion of the Cyprus nesting cohort using each foraging region did not change significantly, with the exception that individuals foraging in the Adriatic region are only present in the Cyprus nesting population from 2012. Repeat satellite tracking (n = 3) and temporal consistency in isotope ratios (n = 36) of Cyprus females, strongly suggest foraging ground fidelity over multiple decades. Main conclusions This study demonstrates the advantages of combining satellite telemetry and SIA to investigate spatial ecology at a population level. The importance of the Tunisian Plateau for foraging is demonstrated. This study indicates that females generally show high fidelity to foraging grounds and shows a potential recent shift to foraging in the Adriatic region for Cyprus females, while the importance of other regions persists across decades, thus providing baselines to develop and assess conservation strategies.

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Section: Foraging Ground Assignmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial ecology of loggerhead turtles: Insights from stable isotope markers and satellite telemetry

Haywood

Fuller

Godley

et al. 2020

Diversity and Distributions

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Conservation implications of isotopic variation in nails and blood with wetland quality in three species of Australian freshwater turtle

Francis,

Brandis,

Chessman

et al. 2024

Aquatic Conservation

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Australian freshwater turtles are declining, reflecting global turtle trends. Understanding variation in turtle diets and habitat requirements can guide protection and restoration of ecosystems. Diet and niche overlap were investigated in three co‐existing species of turtle—the broad‐shelled turtle Chelodina expansa, the eastern long‐necked turtle C. longicollis and the Macquarie turtle Emydura macquarii, in three rivers in the Murray–Darling Basin, Australia, in relation to environmental variables. Dietary variation in relation to water quality (salinity) and macrophyte cover was investigated using stable isotope analyses (δ15N and δ13C) of turtle tissues (plasma, red blood cell, whole blood and nail) representing food assimilation over different antecedent periods. These stable isotope results were consistent with current dietary understanding based on stomach flushing, indicating that isotope analyses are a non‐invasive method for obtaining dietary information. There were temporal dietary differences, with strong shifts between spring and summer sampling periods, particularly in the blood plasma. Intraspecific variation in diets reflected in δ15N and δ13C related to body size. There was evidence of high dietary overlap among the three species, potentially creating competition, particularly when they co‐occur or resources might be limited. Continued degradation of turtle habitats and water quality affects turtle diet and reduces habitat availability, forcing the three species of turtle to co‐exist in diminishing refugia, increasing interspecific competition for food. Protecting and restoring freshwater ecosystems, including maintaining freshwater refugia, is essential to conserve already declining populations of the three Australian freshwater turtle species.

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Isotopic niche overlap among foraging marine turtle species in the Gulf of Mexico

Weber,

Cullen,

Fuentes

2023

Ecology and Evolution

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Sympatric species may overlap in their use of habitat and dietary resources, which can increase competition. Comparing the ecological niches and quantifying the degree of niche overlap among these species can provide insights into the extent of resource overlap. This information can be used to guide multispecies management approaches tailored to protect priority habitats that offer the most resources for multiple species. Stable isotope analysis is a valuable tool used to investigate spatial and trophic niches, though few studies have employed this method for comparisons among sympatric marine turtle species. For this study, stable carbon, nitrogen, and sulfur isotope values from epidermis tissue were used to quantify isotopic overlap and compare isotopic niche size in loggerhead (Caretta caretta), green (Chelonia mydas), and Kemp's ridley (Lepidochelys kempii) turtles sampled from a shared foraging area located offshore of Crystal River, Florida, USA. Overall, the results revealed high degrees of isotopic overlap (>68%) among species, particularly between loggerhead and Kemp's ridley turtles (85 to 91%), which indicates there may be interspecific competition for resources. Samples from green turtles had the widest range of isotopic values, indicating they exhibit higher variability in diet and habitat type. Samples from loggerhead turtles had the most enriched mean δ34S, suggesting they may forage in slightly different micro‐environments compared with the other species. Finally, samples from Kemp's ridley turtles exhibited the smallest niche size, which is indicative of a narrower use of resources. This is one of the first studies to investigate resource use in a multispecies foraging aggregation of marine turtles using three isotopic tracers. These findings provide a foundation for future research into the foraging ecology of sympatric marine turtle species and can be used to inform effective multispecies management efforts.

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Global review and inventory: how stable isotopes are helping us understand ecology and inform conservation of marine turtles

Cited by 39 publications

References 224 publications

Spatial ecology of loggerhead turtles: Insights from stable isotope markers and satellite telemetry

Spatial ecology of loggerhead turtles: Insights from stable isotope markers and satellite telemetry

Conservation implications of isotopic variation in nails and blood with wetland quality in three species of Australian freshwater turtle

Isotopic niche overlap among foraging marine turtle species in the Gulf of Mexico

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