Ras Al Hadd Research Articles

Testing osteometric species determination on zooarchaeological dolphin remains from Late Neolithic and Early Bronze Age sites in Ash-Sharqiyyah, Sultanate of Oman

Different Late Neolithic and Early Bronze Age sites located in the Ras al-Hadd cape and Ras al-Jinz Bay area (Ash-Sharqiyyah South Governorate, Sultanate of Oman) have provided thousands of zooarchaeological dolphin remains suggesting a strong reliance on the exploitation of these animals. Dolphins are hard to identify to the species level due to a highly comparable interspecies osteological morphology as well as a general lack of extensive osteological reference collections. As a result, such remains are frequently identified as “dolphin”, without any further species identification being undertaken. In this study, we assess whether an osteometric method for distinguishing the nine dolphin species that are present in Omani waters can be used to identify the zooarchaeological specimens. Zooarchaeology by Mass-Spectrometry (ZooMS) was also undertaken on a subset of the specimens but proved ineffective due to the poor preservation of the material in an arid climate. This evidence strengthens the need for effective species identification methods based on traditional zooarchaeological methods. This research is based on our ongoing analysis of the thousands of dolphin remains from the Omani zooarchaeological assemblages.

3D Structure of the Ras Al Hadd Oceanic Dipole

In the Arabian Sea, southeast of the Arabian peninsula, an oceanic dipole, named the Ras Al Hadd (RAH) dipole, is formed each year, lying near the Ras Al Hadd cape. The RAH dipole is the association of a cyclonic eddy (CE) to the northeast, with an anticyclonic eddy (AE) to the southwest. This dipole intensifies in the summer monsoon and disappears during the winter monsoon. This dipole has been described previously, but mostly for its surface expression, and for short time intervals. Here, we describe the 3D structure of this dipole over the 2000–2015 period, by combining colocalized ARGO float profiler data (a total of 7552 profiles inside and outside the RAH dipole) with angular momentum eddy detection and tracking algorithm (AMEDA) surface data. We show first the different water masses in and near the RAH dipole. The presence of the Persian Gulf water (PGW) below 200 m depth is confirmed in both eddies. Arabian Sea high salinity water (ASHSW) is found exclusively in the AE; a layer of fresh and cold water is observed above 100 m depth in both eddies. By analyzing the potential density structures, we show that the CE has a surface-intensified structure while the AE is subsurface-intensified. The sea level anomaly shows a 0.04 m elevation above the AE and a 0.2 m depression over the CE. The CE has a faster geostrophic velocity, (vertical velocity, respectively) 0.6 m s−1 than the AE, 0.15 m s−1 (respectively, 3 m day−1 for the CE and 0.6 m day−1 for the AE). After presenting the vertical structure of the dipole, we show the dominance of the nonlinear Ekman pumping in the CE over the linear pumping affecting the dipole. As a consequence, we explain the CE’s longer lifetime by its intensity and shallowness, and by its sensitivity to the interaction with the atmosphere (in particular the wind stress) and with neighboring eddies. We examined the possible (co)existence of symmetric, barotropic, and baroclinic instabilities in both eddies. These instabilities coexist near the surface in both eddies. They are intensified for the CE, which suggests that the CE is unstable and the AE is rather stable or may need a long time to be unstable.

On the effects of Cyclone Ashobaa on sub-inertial oscillations over the Arabian Sea

Coastally Trapped Waves (CTWs) are studied along the east and north shelves of the Arabian Sea (AS) through field measurements and numerical modeling. A nondispersive barotropic wave, induced by Cyclone Ashobaa, with periods of 10–14 days propagated in wider parts of the shelf. The phase velocities and CTW amplitudes significantly decreased in narrower parts, where a stronger stratification also exists. The long waves are represented by first barotropic and lower bottom trapped modes in deeper and shallower parts of these narrow shelves, respectively. Although the low frequency oscillations, with peak periods of 10–14 days, can be detected in shallow water level data, the wavelet transforms of alongshore currents reveal these long waves exist only in deep waters. This can be attributed to the effect of bottom friction, which causes the effective coastal boundary to move offshore. The Ras al Hadd jet was deflected by the interaction of Cyclone Ashobaa with preexisting eddies and an intensified current was observed where the Ras al Hadd jet crossed the northern shelf.

Structure and Dynamics of the Ras al Hadd Oceanic Dipole in the Arabian Sea

The Ras al Hadd oceanic dipole is a recurrent association of a cyclone (to the northeast) and of an anticyclone (to the southwest), which forms in summer and breaks up at the end of autumn. It lies near the Ras al Hadd cape, southeast of the Arabian peninsula. Its size is on the order of 100 km. Along the axis of this dipole flows an intense jet, the Ras al Had jet. Using altimetric data and an eddy detection and tracking algorithm (AMEDA: Angular Momentum Eddy Detection and tracking Algorithm), we describe the life cycle of this oceanic dipole over a year (2014–2015). We also use the results of a numerical model (HYCOM, the HYbrid Coordinate Ocean Model) simulation, and hydrological data from ARGO profilers, to characterize the vertical structure of the two eddies composing the dipole, and their variability over a 15 year period. We show that (1) before the dipole is formed, the two eddies that will compose it, come from different locations to join near Ras al Hadd, (2) the dipole remains near Ras al Hadd during summer and fall while the wind stress (due to the summer monsoon wind) intensifies the cyclone, (3) both the anticyclone and the cyclone reach the depth of the Persian Gulf Water outflow, and (4) their horizontal radial velocity profile is often close to Gaussian but it can vary as the dipole interacts with neighboring eddies. As a conclusion, further work with a process model is recommended to quantify the interaction of this dipole with surrounding eddies and with the atmosphere.

Movements of green turtles from foraging areas of the United Arab Emirates: regional habitat connectivity and use of marine protected areas

Adult sea turtles migrate between foraging areas and nesting sites that may be 100 s–1000 s of km away. Little is known of the connectivity between these sites in the Arabian region for green sea turtles. We document linkages between two foraging areas in the United Arab Emirates (UAE) with key nesting sites and provide insights on effectiveness of marine protected areas for green sea turtles. Tracking 45 adult green sea turtles Chelonia mydas from foraging areas in the UAE, we show that the primary nesting destination for turtles foraging in Bu Tinah in the UAE is Ras al Hadd in Oman. The turtles use the waters of the UAE, Iran and Oman during breeding migrations and generally stay ~ 20 km off the coast, in waters 10–20 m deep except when crossing the Sea of Oman. Turtles display substantial fidelity to the original foraging sites, often traversing other known foraging sites when returning from the breeding migration. A small proportion of turtles also utilise more than one foraging site. Our data indicate that the Marawah Marine Biosphere Reserve in Abu Dhabi is broadly coincident with the foraging areas of turtles offering substantial protection from fishery activities and that the marine protected area in Ras Al Khaimah would be more effective in protecting green sea turtles if it extended offshore and along the coast. These data may contribute to targeted and effective national and international management and conservation initiatives in the Arabian region.

الخليج: عربي أم فارسي؟ دراسة تاريخية لجذور الصراع وأبعاده وتداعياته

يتميز الخليج العربي بموقعه الاستراتيجي، الذي جعله محط أطماع الدول الاستعمارية منذ فجر التاريخ، وکانت منطقة الخليج العربي على مشارف القرنين الخامس عشر والسادس عشر تمثل تحالفا قبليا کبيرا يضم أراضي الساحل العربي من شبه جزيرة قطر وجزر أرخبيل البحرين حتى رأس الحد، وفي الشمال ساحل لورستان، وعدد من الجزر، من ضمنها جزيرني قشم وهرمز. وکانت هرمز المرکز الإداري والاقتصادي لهذا التحالف. وتتمتع منطقة الخليج بأهمية کبيرة في الميزان السياسي الدولي، منذ القرن الخامس عشر وحتى اللحظة، مما أدى إلى تنافس الدول الکبرى على استعمار المنطقة، وقد احتدم الصراع على هذه المنطقة، بداية من السيطرة البرتغالية والهولندية، ثم الصراع الفرنسي والانجليزي، حتى تحقق لبريطانيا بسط نفوذها والسيطرة الکاملة على الخليج العربي. وبخصوص تسمية الخليج العربي، فإن الرومان قد أسموه «الخليج العربي». وممن أطلق تلک التسمية، المؤرخ الروماني بليني بلينيوس الأصغر، في القرن الأول للميلاد، فطبقا لمقولة عماد الحفيظ إن تسمية الخليج العربي ظلت معروفة منذ قبل الإسلام، واستمرت إلى ما بعد الإسلام، لدى سکان شبه الجزيرة العربية وما جاورها، وهذا يعني، بأن تسمية الخليج العربي ليست حديثة، ولم تظهر بظهور المد العروبي الناصري في خمسينيات القرن العشرين، کما يردد البعض خطأ، وإنما هي أقدم من ذلک بکثير. وقد استمرت الإدعاءات الإيرانية بالبحرين في عقد الستينات من القرن العشرين حتى حدث التغير المفاجئ عند إعلان بريطانيا عن عزمها على الإنسحاب من الخليج العربي قبل نهاية عام 1971م، وعند ذلک حدث التطور الخطير من هذه الإدعاءات، وهنا تصور الشاه أن خروج بريطانيا من الخليج العربي سيحدث فراغا خطيرا، وأن إيران خير من يملأ هذا الفراغ، لهذا غيرت إيران من سياستها نحو شرقي الجزيرة العربية، وبدأت مرحلة (التظاهر بحسن النية والصداقة)، مع هذه المنطقة بأنه من اللازم الاتفاق على صيغة أمنية مشترکة للحفاظ على أمن الخليج العربي. The Arabian Gulf is distinguished by its strategic location, which made it focus of ambitions of colonial countries since dawn of history, and Arab Gulf region on outskirts of fifteenth and sixteenth centuries represented a large tribal alliance that included lands of Arab coast from peninsula of Qatar and islands of Bahrain archipelago to Ras al-Hadd, and in north coast of Lorestan And a number of islands, including islands of Qeshm and Hormuz. Hormuz was administrative and economic center of this alliance. The Gulf region enjoys great importance in international political balance, from fifteenth century until moment, which led to competition of great powers to colonize region, and conflict raged over this region, beginning with Portuguese and Dutch control, then French and English conflict, until Britain achieved extension of its influence And complete control of Arabian Regarding naming Arab Gulf, Romans called it the Arabian Gulf. And who launched that name, Roman historian Pliny Pliny Younger, in first century AD, according to saying of Imad al-Hafeez that designation of Arabian Gulf has been known since before Islam, and continued until after Islam, among inhabitants of Arabian Peninsula and its environs, that is to say, that naming of Gulf Al-Arabi is not modern, and did not appear with emergence of Arab Nasserite tide in 1950s, as some erroneously claim, but rather it is much older than that. Iranian claims continued in Bahrain in 1960s until sudden change occurred when Britain announced its intention to withdraw from Arabian Gulf before end of 1971, and then dangerous development of these claims took place, and here Shah imagined that Britain’s exit from Persian Gulf would create a vacuum. It is dangerous, and that Iran is best person to fill this void. That is why Iran changed its policy towards eastern Arabian Peninsula, and began phase of (pretending of goodwill and friendship), with this region that it is necessary to agree on a common security formula to maintain security of Arab

Submesoscale Dynamics in the Gulf of Aden and the Gulf of Oman

We have investigated the surface and subsurface submesoscale dynamics in the Gulf of Aden and the Gulf of Oman. Our results are based on the analyses of regional numerical simulations performed with a primitive equation model (HYCOM) at submesoscale permitting horizontal resolution. A model zoom for each gulf was embedded in a regional mesoscale-resolving simulation. In the Gulf of Aden and the Gulf of Oman, the interactions of mesoscale structures and fronts instabilities form submesoscale eddies and filaments. Rotational energy spectra show that the Gulf of Aden has a higher ratio of submesoscale to mesocale energy than the Gulf of Oman. Fast waves (internal gravity waves, tidal waves, Kelvin waves) and slow waves (Rossby waves) were characterized via energy spectra of the divergent velocity. Local upwelling systems which shed cold filaments, coastal current instabilities at the surface, and baroclinic instability at capes in subsurface were identified as generators of submesocale structures. In particular, the Ras al Hamra and Ras al Hadd capes in the Gulf of Oman, and the Cape of Berbera in the Gulf of Aden, are loci of submesoscale eddy generation. To determine the instability mechanisms involved in these generations, we diagnosed the Ertel potential vorticity and the energy conversion terms: the horizontal and vertical Reynolds stresses and the vertical buoyancy flux. Finally, the impacts of the subsurface submesoscale eddy production at capes on the diffusion and fate of the Red Sea Water (in the Gulf of Aden) and the Persian Gulf Water (in the Gulf of Oman) are highlighted.

Combining laparoscopy and satellite tracking: Successful round-trip tracking of female green turtles from feeding areas to nesting grounds and back

Adult sea turtles undertake periodic long-distance migrations between foraging and nesting areas during breeding migrations, and an understanding the connectivity between these two important habitats can contribute to efficient conservation planning. We present the first round-trip migrations of three green sea turtles in the Arabian region, from a foraging area to a nesting site and back, along with an interpretation of reproductive behaviour which would not have been possible from open-ended tracks. We studied habitat connectivity between seagrass foraging areas in the UAE and nesting beaches, and used laparoscopy as a diagnostic tool to determine gender and reproductive state to enhance the value of satellite tracking data. We identify habitat connectivity between a foraging area at Bu Tinah in the UAE and a nesting site at Ras al Hadd in Oman, document migratory behaviour in the Arabian region, and demonstrate the enhanced value of combining laparoscopy when satellite tracking sea turtles from foraging areas. The results of our work can help develop bilateral or multi-lateral conservation strategies, contribute to the identification of Important Turtle Areas (ITAs), and support national and regional population assessments. In addition, our findings will complement risk assessments for sea turtles in the face of urban and industrial development, climate change, fishery pressure, and shipping activities. This work successfully linked foraging areas and nesting sites, and our approach can be used to provide value-added benefits to future tracking of sea turtles from foraging areas.

A survey of the genetic diversity of the Loggerhead and Green Sea Turtles of the Sultanate of Oman

The Sultanate of Oman hosts large annual nesting aggregations of up to 23,000 Loggerhead Sea Turtles (Caretta caretta) and 10,000 Green Sea Turtles (Chelonia mydas). Both populations have until now been poorly sampled (eight samples for C. caretta and fifteen for C. mydas). Genetic diversity information is needed for both species because these populations are increasingly threatened as the coastlines of Oman become more developed. It is currently unclear how diverse these rookeries are relative to other rookeries in the Atlantic, Mediterranean, Indian, or Pacific oceans. We explored mitochondrial DNA (mtDNA) diversity in 100 C. caretta from Masirah Island and 42 C. mydas from Ras al Hadd, Oman. We also analyzed C. caretta with four nuclear DNA (nDNA) microsatellites to investigate nuclear diversity. Loggerhead populations in Oman showed extremely low mtDNA diversity, but high nDNA diversity, suggesting isolation of genetically impoverished matrilineal lines, but relatively high male-mediated gene flow. In contrast, C. mydas populations in Oman consist of two clusters of distinct haplotypes that yield extremely high estimates of haplotype and nucleotide diversity relative to other global rookeries. These results describe the diversity of C. caretta and C. mydas rookeries in Oman with implications for global conservation.

Geo-archaeological evidence for a Holocene extreme flooding event within the Arabian Sea (Ras al Hadd, Oman)

The Arabian Sea is regarded as one of the least studied regions in terms of coastal hazards such as tropical cyclones and tsunamis. Parts of the coastline are developing rapidly, especially in Oman. This calls for a proper understanding of the natural processes that act on and affect it. This can be done by investigating the magnitude and impact of past events, in particular on human settlements. By doing this, future risks may not only be scientifically predicted and evaluated, but the damage caused by future events might even be mitigated. Evidence of past extreme wave events is preserved in the onshore stratigraphic record. In addition to this, the coastal zone of Oman is rich in archaeological remains. Presented here are the results of comprehensive mapping and analysis of extreme wave deposits of an archaeological site near Ras al-Hadd, suggesting that the Early Bronze Age site HD-6 was inundated at 4450 cal. BP. An event layer is identified between two settlement phases within the archaeological excavation. A contemporaneous sand bed with a maximum thickness of 0.4 m was mapped in the vicinity of the settlement. Ground penetrating radar surveys allow measurement of the thickness as well as identification of the internal facies architecture of the deposit. A high resolution digital elevation model reveals the coastal geomorphology. It is concluded that the causative event must have been a tsunami that was most likely generated within the Makran Subduction Zone. This interpretation does however, remain tentative at the moment. Archaeological evidence indicates that the site was immediately re-occupied after the event, which attests to a certain resiliences of the Early Bronze Age coastal communities in the region.

A seasonal dipolar eddy near Ras Al Hamra (Sea of Oman)

Trajectories and hydrological data from two Argo floats indicate that warm and salty water at 200–300-m depths was ejected from the coast of Oman, near Ras al Hamra, in spring 2008, 2011, and 2012. This warm and salty water, Persian Gulf Water (PGW), once ejected from the coast, recirculated cyclonically in the western Sea of Oman, but also flowed eastward along the Iranian and Pakistani coasts. There, it was expelled seaward by mesoscale eddies as shown by other float data. Seasonal maps of salinity were computed from all available Argo floats; they showed that, in spring, PGW is present in the middle and north of the Sea of Oman, contrary to fall, when the salinity maxima lie southeast of Ras al Hadd. The ejection of PGW from Ras al Hamra is related here to the influence of a mesoscale dipolar eddy which often appears near this cape in spring. The time-averaged and empirical orthogonal functions of altimetric maps over 11 years for this season confirm the frequent presence and the persistence of this feature. From surface currents and hydrology, deep currents were computed via thermal wind balance, and the associated shear and strain fields were obtained. This deformation field is intense near Ras al Hamra, with an offshore direction. This flow structure associated with the mesoscale dipole explains PGW ejection from the coast. This observation suggests that PGW distribution in the Northern Arabian Sea can be strongly influenced by seasonal mesoscale eddies.

High salinity events in the northern Arabian Sea and Sea of Oman

Moored observations in the northern Arabian Sea (NAS) show substantial velocity, temperature and dissolved oxygen fluctuations, accompanied by episodic high salinity intrusions with maximum values≥37.3 on time scales of 2–10 days after the passage of Cyclone Gonu in 2007. These events are characterized by a rapid increase in temperature, salinity and dissolved oxygen followed by an abrupt decline. The mechanisms behind these high salinity events are investigated using a comprehensive dataset of temperature and salinity profiles from ARGO floats and sea surface height anomaly maps. The spatial and temporal distribution of the Persian/Arabian Gulf outflow to the Sea of Oman is also studied using ARGO profiles. Persian Gulf water (PGW) is mainly measured close to the Strait of Hormuz or along the Oman coast on the continental slope in the Sea of Oman. Both mooring and ARGO data show that high salinity PGW can be advected off the slope and into the interior. More high salinity water is measured in the interior of the Sea of Oman within three months after the Gonu passage in summer 2007, which is caused by the combination effect of the oceanic responses to Cyclone Gonu and a clockwise eddy circulation located at northern Ras al Hadd. At other times, the high salinity water appears more in isolated patches and rare in the interior. This study provides a first look at the high salinity events appearing after Gonu and the properties and dynamics of the PGW in the northern Arabian Sea and Sea of Oman.

Cabled ocean observatories in Sea of Oman and Arabian Sea

An ocean observatory—consisting of a real‐time, cabled array in the Sea of Oman and an internally recording, autonomous mooring array recently upgraded to a cabled array in the northern Arabian Sea—celebrated more than 2500 days of continuous operation in July 2012. The observatory, which measures a range of properties, such as water current velocities, temperature, salinity, pressure, dissolved oxygen, and turbidity, is part of the Lighthouse Ocean Research Initiative (LORI) project [du Vall et al., 2011], which was designed as a pilot project and installed in 2005 in the region off Abu Bakara (Figures 1a and 1b). The initial goal of the project was to prove that an in situ, cabled ocean observatory can return high‐quality scientific data on a real‐time basis over longer time periods than conventional moored systems. That same year, an autonomous array was deployed off Ras al Hadd and on Murray Ridge in the Arabian Sea (Figure 1a).

Detection of low plasma estradiol concentrations in nesting green turtles (Chelonia mydas) by HPLC/Ms‐Ms

In previous studies on nesting green turtles under natural conditions from different geographical regions, 17-β-estradiol (E(2) ) was either undetectable or detected at very low levels. RIA and other related techniques were not sensitive enough to measure low E(2) values in the green turtles. In this study, a sensitive method was used in detecting low hormone concentrations: high performance liquid chromatography with tandem quadruple mass spectrometry (HPLC-MS/MS). Using this technique, estradiol for the first time was detected in nesting green turtles during the peak season (June-October) at Ras Al-Hadd Reserve, Oman. The E(2) values recorded from this study were the highest ever recorded from nesting green turtles in any geographical region, but the levels did not vary significantly throughout different phases of nesting. The presence of E(2) during nesting presumably plays a role in the physiology and behavior of this species. Ras Al-Hadd hosts one of the largest nesting populations of green turtles in the world, and an understanding of their nesting patterns may be of value in conservation and management programs for this endangered species.

Antibiotic resistant bacteria as bio-indicator of polluted effluent in the green turtles, Chelonia mydas in Oman

Antibiotic resistant bacteria were studied as bio-indicators of marine polluted effluents during egg-laying in green turtles. A non-invasive procedure for sampling oviductal fluid was used to test for exposure of turtles to pollution in Ras Al-Hadd, Oman, which is one of the most important nesting beaches in the world. Each sample was obtained by inserting a 15 cm sterile swab gently into the cloacal vent as the sphincter muscle is relaxed and the cloacal lining is unfolded to the outside. Forty turtles were sampled. A hundred and thirty-two species of bacteria from 7 genera were isolated. The dominant isolate was Citrobacter. Among the isolates 60.6% were multiple resistant to 15 tested antibiotics. The dominant resistance to antibiotics was ampicillin followed by streptomycine and sulphamethoxazole. Sampling oviductal fluid for resistant bacteria to antibiotics is valuable way to assess exposure to polluted effluents during feeding and migratory in turtles. Polluted effluents using bacteria as bio-indicator may influence reproductive potential in this endangered species.

Embryonic staging of the Green Turtle, Chelonia mydas (Linnaeus, 1758)

Nineteen embryonic stages of the Green Turtle, Chelonia mydas (Linnaeus, 1758), were described between day 6 and hatching (52 days). Eggs were collected at random from fresh nests approximately 10–12 hours post oviposition. The eggs were placed in a precision incubator adjusted to a narrow temperature range (30±0.05°C). Fundamental development occurred between stages 1–4 with the appearance of the optic cup, otic vesicle, heart, pharyngeal clefts, tail bud and rapid differentiation of the brain. In stages 5–9, there was a significant increase in body size and further differentiation of the brain regions. The carapace and plastron began to appear with plates and scutes. The lens of each eye was large with a pigmented iris; eyelids were present. The paddle-shaped limbs appeared with further development of digits. Pigmentation gradually began to spread over the entire body. In stages 10–19, there was a gradual increase in the size and form of different areas in the head region. The pigmentation was more intense, particularly in the head, neck, carapace and limbs. There was a steady increase in skin thickness with wrinkling and folding, especially in the head, neck and limbs. The limbs exhibited rapid differentiation leading to the formation of flippers with claws. The carapace and plastron, with their plates and scutes, were rapidly taking their final form. The yolk sac began to recede into the abdominal cavity. At hatching, the embryo still maintained an umbilical swelling which disappeared 48 hours later. The pipping stage lasted over 30 hours, with the embryo leaving the egg afterwards. The staging patterns from this investigation will be used as a model to be compared with the staging pattern under natural incubation for the Green Turtle at Ras Al-Hadd.

Cyclone Gonu storm surge in Oman

Super Cyclone Gonu is the strongest tropical cyclone on record in the Arabian Sea. Gonu caused coastal damage due to storm surge and storm wave impact as well as wadi flooding. High water marks, overland flow depths, and inundation distances were measured in the coastal flood zones along the Gulf of Oman from 1 to 4 August 2007. The high water marks peaked at Ras al-Hadd at the eastern tip of Oman exceeding 5 m. The storm surge of Gonu is modeled using the Advanced Circulation Model (ADCIRC). The multi-hazard aspect is analyzed by comparing observations from Cyclone Gonu with the 2004 Indian Ocean Tsunami.

Ultrastructural features and elemental distribution in eggshell during pre and post hatching periods in the green turtle, Chelonia mydas at Ras Al-Hadd, Oman

Eggshells were randomly collected from turtle nests immediately after oviposition and at the end of incubation to examine the ultrastructural features using scanning JSM-5600LV microscopy. Three layers were recognized; an outer calcareous, a middle multistrata and an inner membrane. The calcareous layer had loose nodular units varying in shape and size without interlocking attachments. In freshly laid eggs, each nodular unit had spicules arranged in folded stacks. The spicules became unfolded during incubation, to form radiating configurations. Elemental composition and mapping of the layers were analyzed using energy dispersive spectroscopy (EDS). The elements were unevenly distributed throughout the eggshell and Ca 2+ decreased significantly after hatching. X-ray diffraction was used to identify the crystals of the eggshells. It revealed that nodular units of the calcareous were made up of CaCO 3, as aragonite (91%), calcite (6%) and vaterite (3%). The middle layer consisted of organic amorphous material with aragonite (89%) and calcite (11%). The shell membrane consisted of reticular fibers with crystals predominantly of NaCl halite. Thermogravimetry analysis of the calcareous layer indicated a complete evaporation of bonded H 2O at 480 °C and CO 2 at 830 °C. Using the differential thermal analysis (DTA), aragonite was transformed to stable calcite at 425 °C.

Temperature variations in relation to sex determination and plasma progesterone and estradiol levels during embryogenesis and post hatching in the green turtle, Chelonia mydas, at Ras Al-Hadd Reserve, Oman

Temperature variations in relation to sex determination and plasma progesterone and estradiol levels during embryogenesis and post hatching in the green turtle, Chelonia mydas, at Ras Al-Hadd Reserve, Oman

Changes in plasma levels of adrenaline, noradrenaline, glucose, lactate and CO 2 in the green turtle, Chelonia mydas, during peak period of nesting

Plasma concentrations of stress hormones [adrenaline (ADR), noradrenaline (NR)], lactate, glucose and CO 2 were monitored during peak nesting period (May–October) at different phases of nesting in the green turtle, Chelonia mydas. These include, emergence from sea, excavating body and nest chambers, oviposition, covering and camouflaging the nest and then returning to sea. Turtles that completed all phases of nesting including oviposition before returning to sea were considered “successful” turtles, while those that completed all phases but failed to lay their eggs were “unsuccessful”. Blood samples were taken from the cervical sinus within 5 min of capture to avoid stress due to handling. The turtles were usually sampled for blood between 20:00 and 1:00 h of nesting time to ensure uniformity in the sampling. Plasma ADR and NR values were highly significant ( P < 0.001) in successful turtles over emergence, excavating and unsuccessful turtles. Plasma glucose levels remained stable throughout the nesting phases while lactate levels were significantly higher in successful turtles over the other phases ( P < 0.05) which signifies anaerobic metabolism during nesting. Plasma CO 2 values were negatively correlated with ADR and NR ( r = −0.258, P = 0.03; r = −0.304, P = 0.010), respectively. Hematocrit was significantly higher in successful phase ( P < 0.05) compared to other phases, and this may signify a higher degree of stress in successful turtles. Body temperature were significantly lower ( P < 0.005) in the excavating phase compared to the other three phases. Overall, body temperatures were lower than sand temperatures around the nest, which may indicate a behavioral thermoregulation used by the turtles during nesting. This information will be of value to the ongoing conservation program at Ras Al-Hadd Reserve in the Sultanate of Oman.