Asynchrony between dietary and nutritional shifts during the ontogeny of green turtles (Chelonia mydas) in the Mediterranean

Cardona, Luís; Campos, Patricia; Levy, Yaniv; Demetropoulos, Andreas; Margaritoulis, Dimitris

doi:10.1016/j.jembe.2010.07.004

Cited by 66 publications

(53 citation statements)

References 56 publications

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“…The strong negative correlation found between δ 13 C and δ 34 S was previously undescribed among sea grass habitats and resulted in sulphur being the more informative for this study population. Sulphur was specifically selected for this study because green turtles are thought to feed predominantly on seagrasses within the Mediterranean (Cardona et al 2010) that derive their nutrients from the marine sediments as opposed to the open ocean environment. Benthic macroalgae and seagrasses therefore can vary considerably among sites because the marine sedimentary cycle (reviewed by Thode 1991) produces a wide range in δ 34 S values as the reduction of seawater sulphate to H 2 S in shallow sediments is influenced by rock type and accretion rates.…”

Section: Selecting the Elements For Stable Isotope Analysismentioning

confidence: 99%

“…These include (1) an increase in the survival probabilities of juveniles and sub-adults as industrial fisheries are excluded (Casale 2011, Casale & Heppell 2016, (2) greater foraging re sources reducing the age to sexual maturity , (3) temporal oscillations in sea surface currents, such as those dictated by the Cyprus eddy (Zodiatis et al 2005), that can vary the distribution of pelagic-stage juveniles and thus the number of individuals recruiting to each foraging area (Gaspar et al 2012, Scott et al 2014 or (4) a shift in the ecological conditions within Lake Bardawil so that this site now provides a more suitable foraging resource (El-Bana et al 2002, Abd Ellah & Hussein 2009, Nada et al 2013. To expand on this latter hypothesis, evidence suggests that the reopening and ongoing maintenance of the 2 man-made channels in the western and central part of the lake have significantly reduced salinity levels (1970: 100 ‰, 2012: 46.1 ‰) (Abd Ellah & Hussein 2009, Nada et al 2013 and references therein) and allowed Cymo docea nodosa, the primary dietary item of the green turtle within the Mediterranean (Cardona 2010), to colonise and now dominate the shallow western basin (ElBana et al 2002, Abd Ellah & Hussein 2009). Further corroboration from satellite tele metry indicates that the turtles predominately re main within the beds of C. nodosa (Nada et al 2013) which suggests that they might not forage on the Ruppia Cirrhosa that forms monospecific habitats within the eastern basin, and the only seagrass re corded within the lake prior to the reopening of the channels in 1988 (Lipkin 1977, ElBana et al 2002, Abd Ellah & Hussein 2009).…”

Section: Monitoring Foraging Site Contribution Over Timementioning

confidence: 99%

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Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

Bradshaw¹,

Broderick²,

Carreras³

et al. 2017

Mar. Ecol. Prog. Ser.

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Identifying links between breeding and non-breeding sites in migratory animals is an important step in understanding their ecology. Recognising the relative importance of foraging areas and ascertaining site-specific levels of recruitment can provide fundamental and applied insights. Here, satellite telemetry and the stable isotope ratios (δ 13 C, δ 15 N and δ 34 S) of 230 green turtles Chelonia mydas from a regionally important rookery in northern Cyprus were employed to evaluate the relative importance of 4 foraging areas. A preliminary analysis of stable isotope ratios suggested that a major foraging area had been missed through satellite telemetry as a large proportion of turtles had isotope ratios that did not correspond to sites previously identified. Stable isotope ratios were then employed to select 5 turtles to be fitted with platform terminal transmitters in 2015. All 5 turtles were subsequently tracked to the same location, Lake Bardawil in Egypt. Serially collected tissue samples from 45 females, ranging over 2 to 4 breeding seasons, suggested that foraging site fidelity was very common, with 82% of females exhibiting extremely high temporal consistency in isotope ratios. Quantifying fidelity allowed an evaluation of foraging areaspecific contributions to each breeding cohort over the past 2 decades and demonstrated that recruitment was unequal among sites, and dynamic over time, with Egypt now currently the major contributor to the nesting aggregation. This work demonstrates the utility of stable isotope analysis to elucidate the spatial ecology of cryptic taxa and illustrates how more robust baselines can be assembled against which to measure the success of future marine conservation initiatives.

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Section: Selecting the Elements For Stable Isotope Analysismentioning

confidence: 99%

Section: Monitoring Foraging Site Contribution Over Timementioning

confidence: 99%

Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

Bradshaw¹,

Broderick²,

Carreras³

et al. 2017

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

show abstract

“…Like loggerheads, green turtles feed upon pelagic prey in the first period of their life but then shift to a herbivorous diet, feeding upon benthic seagrasses and algae (Bjorndal 1997). Eventually, large juveniles become fully herbivorous: in the Mediterranean, such a stage is reached at a size over 62 cm CCL (Cardona et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Movement patterns of marine turtles in the Mediterranean Sea: a review

Luschi

Casale

2014

Italian Journal of Zoology

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Understanding the at-sea spatial behaviour of sea turtles is a priority for their conservation. In the present paper, the current information on the distribution and movement patterns of the two species breeding in the Mediterranean, the loggerhead and the green turtle, is reviewed, focusing mainly on the 195 published routes of satellite-tracked turtles. A satisfactory level of knowledge about adults' migrations and other movements is reached only for loggerheads breeding at Zakynthos Island, Greece, and for green and loggerhead females nesting in Cyprus, while studies at foraging grounds are limited to loggerheads in the western and central parts of the basin. Adult males and females mostly show quite uniform post-breeding migratory patterns, typically moving towards individually specific neritic foraging grounds. A much higher variability is shown by loggerhead juveniles, which is probably associated with differences in their spatial behaviour while in oceanic or neritic waters. Evidence of seasonal migrations driven by lower temperatures in winter is available only for adult and juvenile loggerheads frequenting the two northernmost parts of the basin, i.e. the Ligurian and the northern Adriatic Sea. Current knowledge gaps and priorities for further research in the Mediterranean are discussed.

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“…Furthermore, loggerhead and green turtles feed upon pelagic prey in the first period of their life, and then switch to benthic prey and seagrasses or algae, respectively (Bjorndal 1997). In the Mediterranean, isotopic signatures indicate that the 2 species still have a similar diet at a size of 25 cm CCL (Cardona et al 2010), corresponding to an age > 2 yr (Casale et al 2009a, Goshe et al 2010.In this study, simulations of the dispersal of sea turtle hatchlings in the Mediterranean were performed using a total of 38 and 10 nesting sites of loggerhead and green sea turtles, respectively. These included (Fig.…”

mentioning

confidence: 99%

“…Green turtles are also reported from the Aegean and Ionian (south Peloponnesus, Greece), while in the south-central zone juveniles and adults frequent Libyan, and to a lesser extent Tunisian waters (Broderick et al 2007, Casale & Margaritoulis 2010, Turkecan & Yerli 2011. N aturally, as they grow, green turtles in creasingly feed upon benthic seagrasses and algae until they become fully herbivorous at a size > 62 cm CCL in the Mediterranean (Cardona et al 2010). This may affect their habitat requirements and may result in a distribution and fi delity to foraging areas different from loggerhead turtles (e.g.…”

mentioning

confidence: 99%

The first ‘lost year’ of Mediterranean sea turtles: dispersal patterns indicate subregional management units for conservation

Casale¹,

Mariani²

2014

Mar. Ecol. Prog. Ser.

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Identifying highly frequented areas is a priority for sea turtle conservation, and the distribution of young individuals in open waters represents a major knowledge gap due to methodological biases. The drift of hatchlings from 38 loggerhead Caretta caretta and 10 green Chelonia mydas turtle nesting sites in the Mediterranean was simulated for the first 6 mo of life, with simulations repeated for 5 different years (2001 through 2005). Results indicate that hatchlings from the Levantine and south-central Mediterranean sites are mainly retained in the same areas of origin, while those from the Ionian area mainly disperse to the Ionian, Adriatic and southcentral Mediterranean areas. Combining hatchling dispersal with existing empirical information on juveniles and adults, a general distribution model among nesting sites, and oceanic and neritic foraging grounds for Mediterranean sea turtles is proposed. The Levantine zone may be particularly key for the conservation of the Mediterranean populations of both species, since it may host the highest concentration of individuals. Subregional management units identified by dispersal patterns may facilitate turtle conservation through a relatively small-scale international approach. In-water studies in specific zones are identified as a research priority for improving current knowledge and informing conservation plans. KEY WORDS: Caretta caretta · Chelonia mydas · Loggerhead turtle · Green turtle · Dispersal · Conservation · Mediterranean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 498: [263][264][265][266][267][268][269][270][271][272][273][274] 2014 turtle species could potentially inform conservation plans for their respective Mediterranean populations (e.g. Schofield et al. 2013).The loggerhead turtle is the most abundant sea turtle species in the Mediterranean, and reproduces mainly in Greece, Turkey, Cyprus and Libya (Casale & Margaritoulis 2010). Loggerhead turtles frequent the entire marine area of the Mediterranean, with high occurrences reported in the oceanic zones of (1) the westernmost part of the basin (from the Alboran Sea to the Balearic Islands), where most individuals are of Atlantic origin (Carreras et al. 2006), (2) the Strait of Sicily, and (3) the Ionian Sea. Loggerheads are also found in high abundance in the neritic zones in the north Adriatic, off Tunisia-Libya, off Egypt, and off the southeast coast of Turkey (Casale & Margaritoulis 2010). Green turtles primarily reproduce on nesting beaches in Turkey, Cyprus and Syria (Casale & Margaritoulis 2010). They primarily occupy neritic areas in the easternmost part of the basin, in addition to foraging areas in Greece and Libya (Casale & Margaritoulis 2010).Current knowledge on the distribution of sea turtles in the Mediterranean waters is based on data from strandings (Tomás et al. 2008, Türkozan et al. 2013, incidental catch in fishing gear (reviewed by Casale 2011), tag returns (Margaritoulis et al. 2003, Casale et al. 2007b, Revelles et...

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Asynchrony between dietary and nutritional shifts during the ontogeny of green turtles (Chelonia mydas) in the Mediterranean

Cited by 66 publications

References 56 publications

Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

Movement patterns of marine turtles in the Mediterranean Sea: a review

The first ‘lost year’ of Mediterranean sea turtles: dispersal patterns indicate subregional management units for conservation

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