Are anthropogenic factors affecting nesting habitat of sea turtles? The case of Kanzul beach,Riviera Maya-Tulum (Mexico)

Marine coast modification and human pressure affects many species, including sea turtles. In order to study nine anthropogenic impacts that might affect nesting selection of females, incubation and hatching survival of loggerhead (Caretta caretta) and green turtle (Chelonia mydas), building structures were identified along a 5.2 km beach in Kanzul (Mexico). A high number of hotels and houses (88; 818 rooms), with an average density of 16.6 buildings per kilometer were found. These buildings form a barrier which prevents reaching the beach from inland, resulting in habitat fragmentation. Main pressures were detected during nesting selection (14.19% of turtle nesting attempts interrupted), and low impact were found during incubation (0.77%) and hatching (4.7%). There were three impacts defined as high: beach furniture that blocks out the movement of hatchlings or females, direct pressure by tourists, and artificial beachfront lighting that can potentially mislead hatchlings or females. High impacted areas showed lowest values in nesting selection and hatching success. Based on our results, we suggest management strategies to need to be implemented to reduce human pressure and to avoid nesting habitat loss of loggerhead and green turtle in Kanzul, Mexico.     

Migratory activity by hatchling loggerhead sea turtles (Caretta caretta L.): evidence for divergence between nesting groups

The South Florida subpopulation of loggerhead sea turtles (Caretta caretta L.) nests with great fidelity on either the southeast or the southwest coast of Florida, USA. The hatchlings that emerge from those nests must swim in opposite directions and search for different surface currents to migrate away from continental shelf waters. In this laboratory study, we compared the pattern of swimming activity shown by the hatchlings from each coast over the first 6 days of migration. Turtles from both coasts were equally active during their “frenzy” period (the first 24 h of swimming) and during the daylight hours of the 5 days that followed (the “postfrenzy” period). However, the west coast turtles were significantly more active than the east coast turtles during the nocturnal portion of the postfrenzy period. This difference may be related to the greater distance southwest coast turtles must negotiate to locate surface currents for transport out of the Gulf of Mexico and into the Atlantic Ocean basin. These differing behavioral strategies may be genetically determined, as similar correspondence between activity and distance is well known among migratory populations of birds and fish and is often based upon inherited programs of endogenously driven activity. Alternatively, behavioral differences between the two nesting groups could be a manifestation of phenotypic plasticity that arises as the hatchlings respond to unique environmental cues on each coast.     

Influence of emergence success on the annual reproductive output of leatherback turtles

Reproductive output of leatherback turtles (Dermochelys coriacea) is affected by the stochastic nature of emergence success. Average emergence success of nests at Playa Grande, Costa Rica was 0.38 ± 0.27. Incubation temperature affected development of leatherback turtle eggs and emergence of hatchlings from the nest. We found that high temperatures reduced hatching success and emergence rate and increased embryonic mortality both early and late during incubation at Playa Grande. There was a temporal effect on emergence success that resulted in more hatchlings being produced at the beginning of the season, because of higher emergence success, than toward the end. Likewise, production of hatchlings varied from year to year. The average annual reproductive output was 252 ± 141 hatchlings per female. The 2005–2006 nesting season had the highest emergence success and produced the greatest number of hatchlings per female compared to the 2004–2005 (+120%) and 2006–2007 (+41%) seasons. However, average clutch size (62 ± 10) and clutch frequency (9.45 ± 1.63), were not different among years. Turtles that had nested a high number of years exhibited greater clutch frequency and arrived earlier to nest than turtles that had nested in fewer numbers of years. Nesting when environmental conditions favor high developmental success and emergence rate may constitute an advantageous reproductive strategy.     

Breeding biology of the green turtle,Chelonia mydas, (Reptilia: Cheloniidae) on Wan-An Island,Peng-Hu Archipelago,Taiwan. I. Nesting ecology

The nesting season of the green turtle, Chelonia mydas on Wan-An Island, Peng-Hu Archipelago, Taiwan extended from early June to early October in both 1992 and 1993. Turtles nested on 9 of the 11 beaches on the island. The average inter-nesting interval was 14.9 d. A close relationship between the first reemergence time and the tidal cycle was found in the present study. The mean straight carapace length of the adult female was 96.6 cm. Female turtles produced from one to nine egg clutches; the average clutch size was 113 eggs. The mean egg size was 46.9 mm in diameter and 22.7 g in weight. The average incubation period was 49.3 d. The sediment characteristics of the beaches on the island are well within the incubation requirements for green turtle nesting. The average hatching success was 70%, but was lower in the artificial nest. The average size for hatchlings was 46.9 mm in straight carapace length and 22.7 g in body weight. The health of the hatchling is influenced by the adult female size, the nesting depth and the precipitation during incubation.     

Can leftovers from predators be reliably used to monitor marine turtle hatchling sex-ratios? The implications of prey selection by ghost crabs

In marine turtles, the sex of an individual is determined by temperatures experienced during embryonic development. Gonad histological observation is still the only reliable way to determine hatchling sex, hampering the study of reproduction and of the demographic consequences of context-dependent sex-ratios, a subject of interest in a warming planet. We investigated whether hatchling remains from predation by Ocypode cursor can be used to estimate sex-ratio trends in a green turtle rookery at Poilão, Guinea-Bissau (10°52′N, 15°43′W). Sex could be readily determined in 77 and 79% of the predated hatchlings in 2008 and 2009, respectively. By comparing hatchlings killed by crabs, hatchlings accidentally dying on the reefs, and live hatchlings, we show that ghost crabs select the smaller prey, but do not select according to hatchling sex, which is explained by the lack of hatchling size dimorphism in this population. The proportion of male hatchlings was 0.45 ± 0.06 and 0.15 ± 0.06 for early and late-season clutches, respectively, these differences most likely being explained by rainfall. Using leftovers from predation by crabs may be a good solution to non-invasively monitor broad trends in sex-ratios of sea turtles.     

Modelling the fate of marine turtle hatchlings

The SLIM oceanographic model was used to examine the fate of hatchling flatback turtles (Natator depressus) in the first two weeks of their dispersal starting at Wild Duck Island, a major turtle-nesting site in the central Great Barrier Reef region of Australia. We ran simulations to investigate the effects of spring versus neap tides, hatchling's swimming behaviour during their first three days at sea, and the location of nesting beaches. The model predicted that up to 50% of the turtle hatchlings entering the sea from the windward, southern beach remained after 14 days in shallow, nearshore waters, irrespective of tides and swimming. These waters are turbid and may be inhospitable to hatchlings. In contrast >80% of hatchlings dispersing from the leeward, northern beach were dispersed to deeper water (10-40 m) in a quasi-stationary dispersion core centred around 10 km north of the nesting beach after 14 days and the offshore spread of the turtle plume was enhanced by the hatchling's seaward swimming during the first three days. This was due to the presence of a coastal boundary layer and a stagnation zone around the northern side of island, but not the southern side. The model confirmed that dispersal from eastern Queensland flatback turtle rookeries is restricted to the lagoons and coastal waters, and that water circulation and hatchling's swimming control dispersion. The model explains why more turtles nest on the northern than the southern side. This study highlights the usefulness of oceanographic models to increase knowledge about a cryptic life stage of marine turtles.     

The effect of incubation temperature on hatchling quality in the olive ridley turtle, Lepidochelys olivacea, from Alas Purwo National Park, East Java, Indonesia: implications for hatchery management

Nest protection through egg relocation from natural nests into protected hatcheries is a common practice used at rookeries around the world to increase hatchling recruitment into sea turtle populations. However, rarely have the impacts of this practice on hatchling recruitment and quality been assessed. This study investigated the influences of the thermal nest environment of olive ridley turtles Lepidochelys olivacea on emergence success and quality of hatchlings of hatchery nests in Alas Purwo National Park, East Java, Indonesia (2009 and 2010 nesting seasons). Nest temperatures above 34?°C for at least 3 consecutive days during incubation in the hatchery resulted in decreases in emergence success and locomotor performance of hatchlings. The use of the hatchery is recommended due to extremely high predation rate of nests left on the beach; however, altering hatchery management practice by spacing nests one meter apart and providing shade should improve hatchery outcomes now and into the future.     

Satellite telemetry reveals behavioural plasticity in a green turtle population nesting in Sri Lanka

Satellite transmitters were deployed on ten green turtles (Chelonia mydas) nesting in Rekawa Sanctuary (RS-80.851°E 6.045°N), Sri Lanka, during 2006 and 2007 to determine inter-nesting and migratory behaviours and foraging habitats. Nine turtles subsequently nested at RS and demonstrated two inter-nesting strategies linked to the location of their residence sites. Three turtles used local shallow coastal sites within 60 km of RS during some or all of their inter-nesting periods and then returned to and settled at these sites on completion of their breeding seasons. In contrast, five individuals spent inter-nesting periods proximate to RS and then migrated to and settled at distant (>350 km) shallow coastal residence sites. Another turtle also spent inter-nesting periods proximate to RS and then migrated to a distant oceanic atoll and made forays into oceanic waters for 42 days before transmissions ceased. This behavioural plasticity informs conservation management beyond protection at the nesting beach.     

Migratory activity by hatchling loggerhead sea turtles (Caretta caretta L.): evidence for divergence between nesting groups

The South Florida subpopulation of loggerhead sea turtles (Caretta caretta L.) nests with great fidelity on either the southeast or the southwest coast of Florida, USA. The hatchlings that emerge from those nests must swim in opposite directions and search for different surface currents to migrate away from continental shelf waters. In this laboratory study, we compared the pattern of swimming activity shown by the hatchlings from each coast over the first 6 days of migration. Turtles from both coasts were equally active during their “frenzy” period (the first 24 h of swimming) and during the daylight hours of the 5 days that followed (the “postfrenzy” period). However, the west coast turtles were significantly more active than the east coast turtles during the nocturnal portion of the postfrenzy period. This difference may be related to the greater distance southwest coast turtles must negotiate to locate surface currents for transport out of the Gulf of Mexico and into the Atlantic Ocean basin. These differing behavioral strategies may be genetically determined, as similar correspondence between activity and distance is well known among migratory populations of birds and fish and is often based upon inherited programs of endogenously driven activity. Alternatively, behavioral differences between the two nesting groups could be a manifestation of phenotypic plasticity that arises as the hatchlings respond to unique environmental cues on each coast.     

Strong site fidelity and longer internesting interval for solitary nesting olive ridley sea turtles in Brazil

Olive ridley sea turtles display two different types of nesting behavior: in arribada (synchronous mass nesting) or solitarily. Contrarily to arribadas, little has been published about solitary nesters. This study aimed to expand the knowledge on internesting interval and site fidelity of solitary nesting olive ridleys and to test a possible development of arribada nesting behavior. Data were collected in Sergipe (Brazil) over 125 km of beach from 10°30′S/36o23′W to 11°26′S/37o19′W, between nesting seasons 2004/2005 and 2006/2007. From 962 tagged females, 173 were seen renesting. The average internesting interval found was longer (22.35 ± 7.01 days) than previously described, which might relate to lower water temperatures during the internesting period. Olive ridleys at Sergipe showed high nesting site fidelity, with consecutive nesting events occurring in close proximity, non-randomly and dependently of previous events. Most of the consecutive nests were separated by 4.06–5.59 km. Development of arribada nesting behavior was not confirmed.     

Some observations of sea turtle nesting activity in Costa Rica

Low level aerial observations were used to obtain synoptic records of the distribution of sea turtle nesting activity along both coasts of Costa Rica. Pertinent environmental information was simultaneously recorded including beach characteristics, river effluents, and evidence of coastal currents. Other correlative information was obtained from detailed maps, current charts, and climatological data. On the Caribbean coast, as expected, green turtle (Chelonia mydas) nesting was concentrated on the beaches between the Tortuguero and Parismina Rivers. On the Pacific coast, two major nesting beaches for the Pacific ridley Lepidochelys olivacea were found, each having over 100 thousand turtles aggregated offshore during the peak period between September and November. Aggregations were present at least from July through December. Massed nesting occurs each year on these same beaches and the event is known as the salida de flota by the natives of Guanacaste Province. Numerous less important nesting beaches were also found. Nesting density did not correlate well with beach quality but, instead, appeared to be related to the proximity of the beach to offshore currents. Oceanic current systems apparently facilitate the transport of sea turtles to the general vicinity of the important nesting beaches on both coasts of Coata Rica.Contribution No. 1557 from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA.     

A light and electron microscope investigation of gametogenesis in Nicolea zostericola (Polychaeta: Terebellidae)

A light and electron microscope study was conducted on Nicolea zostericola (Oersted: Grube, 1860) to describe the processes of gametogenesis. N. zostericola is a monotelic species which spawns from 2 to 5 times over a period of 2 weeks at the end of its 1-year life span. The gonads consist of plates of cells bulging from beneath the peritoneum in the thoracic region of the body. Oogenesis has been divided into 3 phases: an ovarian phase in which gametogonia and primary oocytes are retained within the ovary, a follicular phase, in which oocytes are ovulated into the coelom surrounded by several layers of follicle cells and the vitellogenic phase, where individual oocytes rupture through the follicle cells and enter the coelomic fluid where cell growth and yolk synthesis occur. The combined ovarian and follicular phases have a duration of about 3 to 5 weeks and the vitellogenic phase about 5 to 6 months. Vitellogenesis is described on the ultrastructural level. Yolk synthesis involves the participation of the Golgi apparatus and endoplasmic reticulum of the oocyte in possible combination with nutrient absorption from the coelomic fluid. Spermatogenesis involves the rupturing of masses of spermatogonia into the coelom from the testis, surrounded by peritoneal cells. Smaller clusters of spermatocytes are later released into the coelomic fluid where mitotic and meiotic divisions eventually produce flattened plates of sperm. The mature spermatozoan possesses an elongate head, atypical for most polychaetes.     

Effects of gamma-aminobutyric acid on the settlement of larvae of the black chiton Katharina tunicata

Laboratory-cultured larvae of the black chiton Katharina tunicata (Wood), collected from central California in May and June of 1979 and 1980, settled preferentially on the encrusting coralline alga Lithothamnium sp. Metamorphosis, which involves the loss of the prototrochal ciliary band, occurred within a period of 2.5 h after larvae began crawling upon the alga. In response to gamma-aminobutyric acid (GABA) at a concentration of 10^-6 M, the lecithotrophic trochophore larvae ceased swimming and settled rapidly. Developmental metamorphosis did not follow settlement in the absence of encrusting coralline alga. However, when both GABA and Lithothamnium sp. were present, larval metamorphosis occurred within 2 h of settlement. Significantly different rates of settlement exist for sibling larvae of different ages; 12 d-old larvae responded more rapily and in greater numbers to treatment with GABA than 10 d-old larvae. Differences in settling rates are attributed to the onset of metamorphic competence.     

Estimates of vital rates for a declining loggerhead turtle (Caretta caretta) subpopulation: implications for management

Because subpopulations can differ geographically, genetically and/or phenotypically, using data from one subpopulation to derive vital rates for another, while often unavoidable, is not optimal. We used a two-state open robust design model to analyze a 14-year dataset (1998–2011) from the St. Joseph Peninsula, Florida (USA; 29.748°, ?85.400°) which is the densest loggerhead (Caretta caretta) nesting beach in the Northern Gulf of Mexico subpopulation. For these analyses, 433 individuals were marked of which only 7.2 % were observed re-nesting in the study area in subsequent years during the study period. Survival was estimated at 0.86 and is among the highest estimates for all subpopulations in the Northwest Atlantic population. The robust model estimated a nesting assemblage size that ranged from 32 to 230 individuals each year with an annual average of 110. The model estimates indicated an overall population decline of 17 %. The results presented here for this nesting group represent the first estimates for this subpopulation. These data provide managers with information specific to this subpopulation that can be used to develop recovery plans and conduct subpopulation-specific modeling exercises explicit to the challenges faced by turtles nesting in this region.     

Growth and form in the reef-building coral Montastrea annularis

The in-situ growth rate of the reef coral Montastrea annularis on a reef at Jamaica, W. Indies was determined for a 1-year period using Alizarin Red-S staining techniques. Growth rate is correlated with water depth and growth form. The flattened growth form of M. annularis allows for continued rapid increase in colony surface area at low light intensities. The geomorphology of Jamaican reefs may in part be controlled by the population ecology of M. annularis.     

Interactions among endocrinology,seasonal reproductive cycles and the nesting biology of the female green sea turtle

We collected data on plasma levels of testosterone+5a-dihydrotestosterone (T+DHT) and corticosterone (CORT) from adult female green sea turtles (Chelonia mydas) from southern Queensland during distinct stages of their reproductive cycle. Those females capable of breeding in a given year had elevated plasma steroid levels (T+DHT 0.91ǂ.08; CORT 1.05ǂ.29 ng/ml), associated with follicular development, until courtship began in October. At the beginning of the nesting season in November plasma levels of CORT were related to when the female first nested (r²=0.06; F=10.45; P=0.01). However, they were not correlated with the number of clutches a female laid in that season (F=3.65; P=0.08). We repeatedly sampled 23 turtles over the nesting season and profiled changes in steroids immediately following oviposition of each clutch. Levels of T+DHT (range 0.41-0.58 ng/ml) and CORT (range 2.13-2.81 ng/ml) were similar through the early stages of the nesting season and inter-nesting period, and declined to near basal levels (T+DHT 0.37ǂ.03 and CORT 1.85-ng/ml) following the last clutch for the season. Steroid hormone levels were also low (T+DHT 0.38ǂ.16; CORT 0.46ǂ.21 ng/ml) in four independent post-breeding (atretic) females; samples for these females were taken at a time when body condition was presumably at the lowest for the season. Subtle changes in the nesting environment, such as variation in nesting habitat or the time of night that nesting occurred, were associated with a small and slow CORT increase. We suggest CORT is increased in nesting females to assist in lipid transfer to prepare the ovarian follicles and/or the reproductive organs for ovulation.     

Migratory and reproductive movements of male leatherback turtles (<Emphasis Type="Italic">Dermochelys coriacea</Emphasis>)

The biology of the endangered leatherback turtle (Dermochelys coriacea) at sea is poorly understood. As research has been almost exclusively limited to studies of nesting females, the movements of male turtles and the timing and location of mating activity have remained unknown. We report on the first deployments of satellite tags on male leatherbacks. Male migration to and residency in waters adjacent low-latitude nesting beaches in the western Atlantic suggest that this is where mating occurs, and return migration to these areas reveals male fidelity for breeding sites. Rate of travel decreased markedly after arriving in coastal breeding areas, where males remained for up to 96 days before assuming northward migrations. The initiation of these northward migrations coincided with peak nesting activity in adjacent nesting colonies. Data from satellite-linked time-depth recorders attached to two males revealed diel dive patterns in breeding areas and marked differences in diving behaviour between migratory and breeding periods in one turtle. When male turtles were in waters adjacent nesting colonies, their movements differed from those reported for nesting females, with females ranging farther from shore. Our results suggest that male leatherbacks may be vulnerable to entanglement in coastal fishing gear in waters adjacent nesting beaches.Communicated by R.J. Thompson, St. Johns     

Trans-Pacific dispersal of loggerhead turtle hatchlings inferred from numerical simulation modeling

We used Lagrangian numerical simulations to examine the trans-Pacific dispersal processes of loggerhead turtle hatchlings. Ten thousand simulated particles were released from each of the three nesting regions in Japan and tracked for 5 years. Results showed many particles moving eastward, drifting in the Kuroshio Current followed by the Kuroshio Extension Current. However, no particles reached Baja California, a known feeding area, through passive processes, indicating that trans-Pacific transportation requires active swimming by turtles. The duration of the trans-Pacific dispersal was estimated to be at least 1.6–3.4 years, with some turtles drifting in the Kuroshio Countercurrent and remaining in the western Pacific even after 5 years. This indicates that as revealed by previous genetic studies, not all loggerheads always disperse along a trans-Pacific route. The findings showed that survival and expected growth rates varied widely according to ambient temperatures during drifting, which in turn depended on nesting location.     

Population structure and genetic diversity in green turtles nesting at Tortuguero,Costa Rica,based on mitochondrial DNA control region sequences

The green turtle (Chelonia mydas) nesting population at Tortuguero, Costa Rica, is the largest nesting aggregation in the Atlantic, by at least an order of magnitude. Previous mitochondrial DNA (mtDNA) surveys based on limited sampling (n = 41) indicated low genetic diversity and low gene flow with other Caribbean nesting colonies. Furthermore, a survey of nuclear DNA diversity invoked the possibility of substructure within the Tortuguero rookery. To evaluate these characteristics, mtDNA control region sequences were determined for green turtles nesting at Tortuguero in 2001 (n = 157) and 2002 (n = 235). The increased sample revealed three additional haplotypes; five haplotypes are now known for Tortuguero female green turtles. Analyses of molecular variance indicated that there was no significant spatial population structure along the 30-km nesting beach. In addition, no temporal population structure was detected either between the two nesting seasons or within the nesting season. As a result of the larger sample size and additional haplotypes, estimates of genetic separation among Caribbean nesting colonies have changed and the concordance of phylogenetic and phylogeographic patterns reported in the past for green turtles in the Greater Caribbean has weakened. The five haplotypes from Tortuguero represent 36% of the haplotypes identified in green turtle nesting aggregations in the Greater Caribbean and 17% of the haplotypes known to occur in nesting or foraging aggregations in the Greater Caribbean. Haplotype diversity (0.16) and nucleotide diversity (0.0034) for the Tortuguero population are substantially lower than those for the combined rookeries in the Greater Caribbean (0.44 and 0.0078, respectively). Although comprehensive evaluation of regional genetic diversity requires nuclear DNA data, our study indicates that conserving genetic diversity in Caribbean green turtles will require careful management of the smaller rookeries in addition to the Tortuguero rookery.     

Molecular characterization of symbiotic algae (Symbiodinium spp.) in soritid foraminifera (Sorites orbiculus) and a scleractinian coral (Orbicella annularis) from St John,US Virgin Islands

The exchange of Symbiodinium symbionts among scleractinian and soritid hosts could facilitate acclimatization to changing conditions by establishing novel symbiotic unions better tuned to prevailing conditions. In this study, we compare the communities of Symbiodinium spp. in neighboring populations of Orbicella annularis and Sorites orbiculus from St. John, US Virgin Islands, using operational taxonomic unit (OTU) clustering of cloned internal transcribed spacer 2 (ITS-2) rDNA sequences. We tested for partitioning of Symbiodinium OTUs by host and depth within and between two sites to explore the potential for symbiont exchange between hosts and light-dependent microhabitat specialization. An apparent lack of overlap in Symbiodinium communities (13 OTUs representing 7 clades) hosted by O. annularis and S. orbiculus suggests that exchange among these hosts does not occur. A low number of novel clade G ITS-2 sequences were found in one O. annularis and one S. orbiculus. A phylogenetic analysis of these sequences revealed them to be sub-clade G2 Symbiodinium, which are most commonly hosted by excavating clionid sponges. A permutational MANOVA revealed within host differences in the partitioning of Symbiodinium OTUs by site but not depth. This finding highlights the potential roles of either dissimilar environmental conditions between sites, or at least partial separation between populations, in determining the types of Symbiodinium contained in different hosts on a spatial scale of a few kilometers.