Stable isotopes reveal dietary differences and site fidelity in juvenile green turtles foraging around São Tomé Island, West Central Africa

Hancock, JM; Vieira, Sara; Jiménez, Vladimir; Rio, Jonathan; Rebelo, Rui

doi:10.3354/meps12633

Cited by 22 publications

(28 citation statements)

References 77 publications

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“…However, a study in an eastern Pacific population did not find differences in diet between adults and immature stages suggesting a lack of ontogenetic dietary shift and that adults remained omnivores (Lemons et al, ). Studies in the western Pacific and eastern Atlantic found a similar pattern (Shimada et al, ; Hancock et al, ). Further, one study detected an asynchronous shift between diet and which dietary components constitute the main nutritional source (protein versus plant matter) (Cardona et al, ).…”

Section: Resultssupporting

confidence: 53%

“…Two species, C. mydas and E. imbricata , are likely to forage at two trophic levels. SIAs have revealed cryptic diets in adult C. mydas with some populations being clearly omnivorous and others herbivorous, in contrast to the longstanding view that there is an obligate ontogenetic dietary shift from omnivory to herbivory resulting in adults being specialist herbivores (Hancock et al, ; Hatase et al, , Figs , S3). Two species, D. coriacea and C. caretta, span more than two trophic levels between populations.…”

Section: Resultsmentioning

confidence: 98%

“…herbivory versus carnivory), which are unrelated to changes in spatial habitat use (shift from oceanic pelagic prey to neritic benthic prey). Four studies have investigated this question in C. caretta in Atlantic and Indian Ocean populations (Wallace et al, ; McClellan et al, ; Thomson et al, ; Hall et al, ); 19 studies in Atlantic C. mydas (Burgett et al, ; Cardona et al, ; Di Beneditto, Siciliano & Monteiro, ; Gillis et al, ; Gonzales Carman et al, ; Hancock et al, ; Howell et al, ; Velez‐Rubio et al, ; Williams et al, ), Pacific C. mydas (Arthur, ; Barceló, ; Lemons et al, ; Prior, Booth & Limpus, ; Rodríguez‐Barón, ; Sampson et al, ; Santos‐Baca, ; Shimada et al, ), and C. mydas in the Indian Ocean (Burkholder et al, ) and in the Mediterranean (Cardona et al, ); one study in Atlantic D. coriacea (Wallace et al, ), one study in E. imbricata (Ferreira et al, ), and one study in L. olivacea (Peavey et al, ).…”

Section: Resultsmentioning

confidence: 99%

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Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

2019

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The idea that interspecific variation in trophic morphology among closely related species effectively permits resource partitioning has driven research on ecological radiation since Darwin first described variation in beak morphology among Geospiza.Marine turtles comprise an ecological radiation in which interspecific differences in trophic morphology have similarly been implicated as a pathway to ecopartition the marine realm, in both extant and extinct species. Because marine turtles are charismatic flagship species of conservation concern, their trophic ecology has been studied intensively using stable isotope analyses to gain insights into habitat use and diet, principally to inform conservation management. This legion of studies provides an unparalleled opportunity to examine ecological partitioning across numerous hierarchical levels that heretofore has not been applied to any other ecological radiation. Our contribution aims to provide a quantitative analysis of interspecific variation and a comprehensive review of intraspecific variation in trophic ecology across different hierarchical levels marshalling insights about realised trophic ecology derived from stable isotopes.We reviewed 113 stable isotope studies, mostly involving single species, and conducted a meta-analysis of data from adults to elucidate differences in trophic ecology among species. Our study reveals a more intricate hierarchy of ecopartitioning by marine turtles than previously recognised based on trophic morphology and dietary analyses. We found strong statistical support for interspecific partitioning, as well as a continuum of intraspecific trophic sub-specialisation in most species across several hierarchical levels. This ubiquity of trophic specialisation across many hierarchical levels exposes a far more complex view of trophic ecology and resource-axis exploitation than suggested by species diversity alone. Not only do species segregate along many widely understood axes such as body size, macrohabitat, and trophic morphology but the general pattern revealed by isotopic studies is one of microhabitat segregation and variation in foraging behaviour within species, within populations, and among individuals.These findings are highly relevant to conservation management because they imply ecological non-exchangeability, which introduces a new dimension beyond that of genetic stocks which drives current conservation planning.Perhaps the most remarkable finding from our data synthesis is that four of six marine turtle species forage across several trophic levels. This pattern is unlike that seen in other large marine predators, which forage at a single trophic level according to stable isotopes. This finding affirms suggestions that marine turtles are robust sentinels of ocean health and likely stabilise marine food webs. This insight has broader significance for studies of marine food webs and trophic ecology of large marine predators.Beyond insights concerning marine turtle ecology and conservation, our findings also have broader impli...

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Section: Resultssupporting

confidence: 53%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

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Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

2019

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“…Macroalgae dominant. Macroalga is consumed most abundantly in the following sub-regions: Pacific N Central (mean = 96.0%; SE = 1.9; n = 6; e.g., Arthur and Balazs 2008;Balazs et al 1987), Atlantic E (mean = 62.5; SE = 7.5; n = 2; e.g., Hancock et al 2018), Atlantic SW (mean = 59.5%; SE = 13.9; n = 9) especially tropical areas (e.g., Reisser et al 2013), Pacific S Central (mean = 58.5; SE = 41.5; n = 2; e.g., Piovano et al 2020;Balazs 1983), Pacific NW (mean = 52.5%; SE = 9.4; n = 4), Indian SE (mean = 51.7%; SE = 14.2; n = 5; e.g., Shimada et al 2014;Fukuoka et al 2016), Pacific E (mean = 49.4%; SE = 7.7; n = 18; e.g. Seminoff et al 2002;Arthur and Balazs 2008;Carrión-Cortez et al 2010;Quiñones et al 2010), and Atlantic NW (mean = 34.1%, SE = 7.7; n = 19) especially high in temperate areas (e.g., Holloway-Adkins and Hansiak 2017).…”

Section: Global Review Of Green Turtle Dietmentioning

confidence: 99%

A global review of green turtle diet: sea surface temperature as a potential driver of omnivory levels

et al. 2020

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To better understand dietary requirements, trophic shifts, and trophic interactions of the threatened green turtle (Chelonia mydas), we conducted a comprehensive global review and literature tabulation (177 studies) reporting diets of individuals > 25 cm carapace length. We analysed those studies involving natural sites and healthy animals that reported relative proportions of all diet components (67 studies, 89 datasets at 75 sites, 13 geographic sub-regions, 3 oceans). We compared diets by sub-region and foraging site relative to four diet components, i.e., seagrass, macroalgae, terrestrial plants (including mangroves) and animal matter. To assess sea surface temperature (SST) as an environmental driver, values were extracted from satellite data (single year) and site-specific observations (study durations) and examined relative to diet composition. Satellite data indicated that at warmer sites with temperatures > 25 °C (≥ 6 months annually), diet was predominantly herbivorous (mean = 92.97%; SE = 9.85; n = 69 datasets). At higher latitude sites and in cold-water currents with SST < 20 °C (≥ 6 months annually), dietary animal matter featured prominently (mean = 51.47%; SE = 4.84; n = 20 datasets). Site-specific observations indicated that SST had a small but significant effect on contributions of animal matter (r2 = 0.17, P = < 0.001) and seagrass (r2 = 0.24, P = < 0.001) but not macroalgae and terrestrial plants. Our study presents the first quantitative evidence at a global scale that temperature may be an important driver of omnivory, providing a new perspective on variations in green turtle diet, especially in light of global warming and climate change.

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“…The marine phase accounts for most of the sea turtles' lives and is characterized by complex migration patterns that include periodic returns to specific geographic areas, such as coastal foraging grounds [52]. After an initial oceanic stage, sea turtles settle in a neritic environment and often stay in small home ranges for several years [55] and select, at a finer scale, specific resources available within neritic habitats [56][57][58][59]. However, sea turtles in the neritic stage can travel across oceanic waters when moving between different foraging grounds, and adult fisheries.gov.fj).…”

Section: Introductionmentioning

confidence: 99%

Soundscape of green turtle foraging habitats in Fiji, South Pacific

et al. 2020

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The soundscape features of the marine environment provide crucial information about ecosystem health for many species, and they are defined by the local biological, geophysical, and anthropogenic components. In this study, we investigated the soundscape at green turtle neritic foraging habitats in Fiji, South Pacific, with the aims of characterizing the contribution of each component and of comparing the levels of acoustic pressure among sites with different abundances of sea turtles. Four sites were selected at two islands, and one hydrophone was deployed at each site. Generalized additive models highlighted that sound pressure levels (SPLs) at low frequencies (125-250 Hz) were especially affected by wind conditions, while at higher frequencies (>250 Hz) SPLs were mostly influenced by fish and crustacean acoustic activity. Higher abundances of green turtles were found at sites with the highest levels of SPLs and the highest number of acoustic emissions by fishes and crustaceans but were not related to maximum seagrass and macroalgae coverage, or the highest number of fish. The selected coastal habitats have negligible anthropogenic noise, thus this study informs physiological and behavioral studies of the acoustic signatures that sea turtles might target and provides a baseline against which potential impact of soundscape changes on sea turtle spatial abundance and distribution can be evaluated.

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Stable isotopes reveal dietary differences and site fidelity in juvenile green turtles foraging around São Tomé Island, West Central Africa

Cited by 22 publications

References 77 publications

Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

A global review of green turtle diet: sea surface temperature as a potential driver of omnivory levels

Soundscape of green turtle foraging habitats in Fiji, South Pacific

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