ARCHELON

Athens, Greece
Athens, Greece

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PubMed | University of Exeter, University of Barcelona, ARCHELON and National and Kapodistrian University of Athens
Type: Journal Article | Journal: Marine biology | Year: 2017

Many marine megavertebrate taxa, including sea turtles, disperse widely from their hatching or birthing locations but display natal homing as adults. We used flipper tagging, satellite tracking and genetics to identify the origin of loggerhead turtles living in Amvrakikos Gulf, Greece. This location has been identified as hosting regionally important numbers of large-juvenile to adult sized turtles that display long-term residency and/or association to the area, and also presents a male biased sex ratio for adults. A total of 20 individuals were linked to nesting areas in Greece through flipper tagging and satellite telemetry, with the majority (16) associated with Zakynthos Island. One additional female was tracked from Amvrakikos Gulf to Turkey where she likely nested. Mitochondrial DNA mixed stock analyses of turtles captured in Amvrakikos Gulf (


Patel S.H.,Drexel University | Morreale S.J.,Cornell University | Saba V.S.,Princeton University | Panagopoulou A.,Drexel University | And 2 more authors.
PLoS ONE | Year: 2016

Sea turtles are vulnerable to climate change impacts in both their terrestrial (nesting beach) and oceanic habitats. From 1982 to 2012, air and sea surface temperatures at major high use foraging and nesting regions (n = 5) of loggerhead turtles (Caretta caretta) nesting in Greece have steadily increased. Here, we update the established relationships between sea surface temperature and nesting data from Zakynthos (latitude: 37.7° N), a major nesting beach, while also expanding these analyses to include precipitation and air temperature and additional nesting data from two other key beaches in Greece: Kyparissia Bay (latitude: 37.3° N) and Rethymno, Crete (latitude: 35.4° N). We confirmed that nesting phenology at Zakynthos has continued to be impacted by breeding season temperature; however, temperature has no consistent relationship with nest numbers, which are declining on Zakynthos and Crete but increasing at Kyparissia. Then using statistically downscaled outputs of 14 climate models assessed by the Intergovernmental Panel on Climate Change (IPCC), we projected future shifts in nesting for these populations. Based on the climate models, we projected that temperature at the key foraging and breeding sites (Adriatic Sea, Aegean Sea, Crete, Gulf of Gabès and Zakynthos/Kyparissia Bay; overall latitudinal range: 33.0° -45.8° N) for loggerhead turtles nesting in Greece will rise by 3-5° C by 2100. Our calculations indicate that the projected rise in air and ocean temperature at Zakynthos could cause the nesting season in this major rookery to shift to an earlier date by as much as 50-74 days by 2100. Although an earlier onset of the nesting season may provide minor relief for nest success as temperatures rise, the overall climatic changes to the various important habitats will most likely have an overall negative impact on this population.


Patel S.H.,Drexel University | Morreale S.J.,Cornell University | Panagopoulou A.,ARCHELON | Bailey H.,University of Maryland Center for Environmental Science | And 4 more authors.
Ecosphere | Year: 2015

While telemetry is an invaluable tool for tracking animal movement patterns, the data generated by this technique is often challenging to interpret. Here, we addressed this issue by developing a novel method, based on changepoint analysis, which incorporated both the horizontal and vertical movement metrics and compared this output to that from a switching state-space model (SSSM) that categorized behavior based on horizontal movement metrics. We deployed 20 satellite transmitters on postnesting loggerhead turtles at Rethymno, Crete, Greece between 2010 and 2011 to monitor their at-sea behavior. We used both models to identify behavioral changes, such as the switches from migration to foraging, and from foraging to overwintering. The satellite-tracked turtles exhibited three discrete migratory strategies, with 9 turtles migrating southwards to the coast of northern Africa, 6 turtles migrating northwards into the Aegean Sea, and 4 turtles remaining resident in the waters of Crete. The SSSM readily identified the switch from transiting to ARS behavior in most animals, but the CPA model was able to distinguish multiple modes and more subtle shifts in behavior corresponding with shifts from migration to foraging to overwintering behaviors. We have shown that by incorporating vertical movement metrics into the analysis of telemetry data, previously hidden shifts in behavior can be revealed. The resulting increase in ability to discern complex behavioral patterns of animals remotely will likely yield better management and conservation decisions for a wide array of organisms. © 2015 Patel et al.


Cardona L.,University of Barcelona | Clusa M.,University of Barcelona | Eder E.,University of Barcelona | Eder E.,CONICET | And 9 more authors.
Marine Ecology Progress Series | Year: 2014

Loggerhead turtles Caretta caretta use a wide variety of foraging strategies, and some populations forage in sub-optimal habitats. Different foraging strategies may not be equivalent in terms of fitness and may result in differences in adult body size and clutch size among populations. Accordingly, we tested whether differences in clutch size among rookeries in the Mediterranean Sea are related to differential use of foraging grounds of contrasting productivity. Stable isotope ratios of carbon and nitrogen of turtle hatchlings from 8 Mediterranean rookeries were used to characterise the foraging grounds of their mothers. Clutch size was also studied in each rookery to assess reproductive output linked to foraging ground productivity. According to stable isotope ratios, most of the females nesting in the considered rookeries foraged in the southern Ionian Sea. The highly productive Adriatic/northern Ionian Sea region was mainly used by females nesting in western Greece. The explanation for these patterns might be linked to water circulation patterns and drifting trajectories followed during developmental migrations, which might determine individual knowledge on the location of productive foraging patches. Average clutch size in each rookery was positively correlated to the proportion of females accessing highly productive areas such as the Adriatic/northern Ionian Sea. This has a strong influence on reproductive output, and hence females using the most productive foraging grounds had the largest clutch sizes. © 2014 Inter-Research.


Clusa M.,University of Barcelona | Carreras C.,University of Barcelona | Pascual M.,University of Barcelona | Demetropoulos A.,Cyprus Wildlife Society | And 10 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2013

As the loggerhead turtle (Caretta caretta) is a philopatric species with a strong genetic structure, the analysis of mtDNA can be used to track evolutionary and colonisation events. In this study we use a genetic approach to understand the population structure of C. caretta in the Mediterranean Sea and to test whether loggerheads could have colonised the Mediterranean during the Pleistocene and survived the cold phases in warm refugia. We amplified a long mtDNA D-loop fragment (815. bp) from 168 dead hatchlings sampled from a selection of rookeries in the Eastern Mediterranean: Libya, Israel, Lebanon, Cyprus and Greece. Previously published data from Turkey and Calabria (Southern Italy) were also included in the analyses. The population nesting in Libya emerged as the oldest population in the Mediterranean, dating from the Pleistocene ca. 65,000. years ago (20,000-200,000). This reveals that the Libyan population might have settled in the Mediterranean basin before the end of the last glacial period. The remaining nesting sites, except Calabria, were subsequently colonised as the population expanded. The populations nesting in Eastern Turkey and Western Greece settled ca. 30,000. years ago (10,000-100,000), whereas the remaining populations originated as a result of a more recent Holocenic expansion. As Calabria presented a unique Atlantic haplotype, found nowhere else in the Mediterranean, we consider this nesting site as the result of an independent colonisation event from the Atlantic and not the recent spread of Mediterranean populations. This reveals that the current genetic structure of C. caretta rookeries in the Mediterranean would be the result of at least two colonisation events from the Atlantic, the oldest one in Libya and a most recent in Calabria, combined with local extinctions during Pleistocenic glaciations and re-colonisations from glacial refugia in Libya, Eastern Turkey and Western Greece. © 2012 Elsevier B.V.


PubMed | Cornell University, ARCHELON, Princeton University and Drexel University
Type: Journal Article | Journal: PloS one | Year: 2016

Sea turtles are vulnerable to climate change impacts in both their terrestrial (nesting beach) and oceanic habitats. From 1982 to 2012, air and sea surface temperatures at major high use foraging and nesting regions (n = 5) of loggerhead turtles (Caretta caretta) nesting in Greece have steadily increased. Here, we update the established relationships between sea surface temperature and nesting data from Zakynthos (latitude: 37.7N), a major nesting beach, while also expanding these analyses to include precipitation and air temperature and additional nesting data from two other key beaches in Greece: Kyparissia Bay (latitude: 37.3N) and Rethymno, Crete (latitude: 35.4N). We confirmed that nesting phenology at Zakynthos has continued to be impacted by breeding season temperature; however, temperature has no consistent relationship with nest numbers, which are declining on Zakynthos and Crete but increasing at Kyparissia. Then using statistically downscaled outputs of 14 climate models assessed by the Intergovernmental Panel on Climate Change (IPCC), we projected future shifts in nesting for these populations. Based on the climate models, we projected that temperature at the key foraging and breeding sites (Adriatic Sea, Aegean Sea, Crete, Gulf of Gabs and Zakynthos/Kyparissia Bay; overall latitudinal range: 33.0-45.8N) for loggerhead turtles nesting in Greece will rise by 3-5C by 2100. Our calculations indicate that the projected rise in air and ocean temperature at Zakynthos could cause the nesting season in this major rookery to shift to an earlier date by as much as 50-74 days by 2100. Although an earlier onset of the nesting season may provide minor relief for nest success as temperatures rise, the overall climatic changes to the various important habitats will most likely have an overall negative impact on this population.


Cardona L.,University of Barcelona | Campos P.,University of Barcelona | Levy Y.,Israel Sea Turtle Rescue Center | Demetropoulos A.,Cyprus Wildlife Society | Margaritoulis D.,ARCHELON
Journal of Experimental Marine Biology and Ecology | Year: 2010

Young green turtles (Chelonia mydas) spend their early lives as oceanic omnivores, which consume primarily animal prey. Once they settle into neritic habitats (recruitment), they appear to shift rapidly into an herbivorous diet in tropical regions. However, the ontogeny of the dietary shift and the relevance of animal prey in the diet of neritic green turtles are poorly understood in subtropical and warm temperate regions. Stable isotopes of carbon and nitrogen in the carapace scutes of 22 green turtles from the eastern Mediterranean, ranging from 28 to 83. cm in curved carapace length (CCLmin), were analysed to test the hypothesis of a rapid nutritional shift following recruitment. Seagrasses prevailed in the stomach contents of all the green turtles that were larger than 30. cm CCLmin, but the concentration of stable isotopes in the carapace scutes revealed that turtles shorter than 40. cm CCLmin derived a negligible amount of assimilated nutrients from seagrasses. The concentration of stable isotopes in the carapace scutes also suggested that the contribution of seagrasses to the nutrients assimilated by green turtles increased steadily with turtle size and that some, but not all, of the turtles larger than 62. cm CCLmin were fully herbivorous. The overall evidence (gut contents analysis and stable isotope analysis) indicates that green turtles in the Mediterranean shift to a seagrass-based diet immediately after recruitment but turtle growth continues to rely on animal-derived nutrients for several years after recruitment. This asynchrony between the dietary and nutritional shifts is thought to be caused by the temperature sensitivity of bacterial fermentation and the low temperatures experienced by green turtles in the Mediterranean, which may result in a poor assimilation of the plant-derived nutrients for most of their neritic juvenile life. © 2010 Elsevier B.V.


Genetic markers have been widely used in marine turtles to assess population structuring and origin of individuals in common feeding grounds, which are key elements for understanding their ecology and for developing conservation strategies. However, these analyses are very sensitive to missing information, especially from abundant nesting sites. Kyparissia Bay (western Greece) hosts the second largest Mediterranean nesting aggregation of the loggerhead turtle (Caretta caretta), but the genetic profile of this nesting site has not, as yet, been described using the extended version of the historically used mitochondrial DNA (mtDNA) marker. This marker was genotyped for 36 individuals nesting at Kyparissia Bay and haplotype frequencies obtained were compared with published data from other Mediterranean nesting sites. The results confirmed the connection between Kyparissia and other western Greek nesting sites and the isolation of this western Greek group from other Mediterranean nesting areas. As a consequence of this isolation, this abundant group of nesting aggregations (almost 30% of the Mediterranean stock) is not likely to significantly contribute to the recovery of other declining Mediterranean units. © 2014 CSIC.


Rees A.F.,ARCHELON | Rees A.F.,University of Exeter | Margaritoulis D.,ARCHELON | Newman R.,ARCHELON | And 4 more authors.
Marine Biology | Year: 2013

Much is still to be learned about the spatial ecology of foraging marine turtles, especially for juveniles and adult males which have received comparatively little attention. Additionally, there is a paucity of ecological information on growth rates, size and age at maturity, and sex ratios at different life stages; data vital for successful population modelling. Here, we present results of a long-term (2002-2011) study on the movements, residency, growth and sex ratio of loggerhead turtles (Caretta caretta) in Amvrakikos Gulf (39°0′N 21°0′E), Greece, using satellite telemetry (N = 8) and ongoing capture-mark-recapture (CMR; N = 300 individuals). Individuals encountered at sea ranged from large juvenile to adult (46. 2-91. 5 cm straight carapace length) and demonstrated growth rates within published norms (<2. 7 cm yr-1) that slowed with increasing body size. We revealed that an unexpectedly high proportion of animals were male (>44 % of captures above 65 cm straight carapace length), compared to region-wide female-biased hatchling production, indicating sex-biased survival or possible behavioural drivers for likelihood of capture in the region. Satellite tracking confirmed that some turtles establish discrete, protracted periods of residency spanning more than 1 year, whilst others migrated away from the site. These findings are underlined by CMR results with individual capture histories spanning up to 7 years, and only 18 % of individuals being recaptured. © 2012 Springer-Verlag Berlin Heidelberg.


Zbinden J.A.,University of Exeter | Bearhop S.,University of Exeter | Bradshaw P.,ARCHELON | Gill B.,ARCHELON | And 3 more authors.
Marine Ecology Progress Series | Year: 2011

Linking foraging and breeding habitats is key to the understanding of behaviour, ecology and demography of migratory species Establishing such connections has long been hampered by the logistical problems of following individuals between foraging and breeding areas, especially in the marine realm We used variation in nitrogen stable isotope patterns between 2 foraging regions of loggerhead sea turtles Caretta caretta determined from samples of satellite-tracked individuals to assign untracked turtles to a foraging region We sought to enhance determination of the relative importance of geographically separated foraging regions and to investigate the relationship between fitness correlates and inferred migratory strategies Of 18 turtles followed by satellite tracking from Zakynthos (Greece), 10 moved north to foraging areas in the Adriatic Sea and the Gulf of Amvrakikos and 8 moved south to foraging areas off the coast of North Africa Of 51 untracked individuals sampled for stable isotope analysis, we considered the stable isotope signature of 47 to qualify for assignment to foraging areas in the north (n = 22) and south (n = 25) Females foraging north were significantly larger (curved carapace length), and the former group laid larger clutches (even after correction for body length) than turtles foraging south, a fact that can be interpreted as a carry-over effect Combining satellite tracking with stable isotope signatures in marine turtles opens new perspectives into how forensic tracking methodologies may be used to scale up knowledge from electronic tracking of a limited number of individuals to sample sizes that are more meaningful from a population perspective © Inter-Research 2011.

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