Sea turtles face a number of threats from climate change. One pertinent threat is the impact of sea level rise (SLR), which can lead to a loss of nesting habitat and reduced survival of embryos due to inundation and erosion. Here we review the impacts of SLR on sea turtles. We examined 34 studies (66 assessments) on SLR impacts across six species and 40 sites globally, with 62.1

Changes in mean adult body size may be a universal response to global warming and sometimes lead to conservation concerns. We show that size reductions in sea turtles are now the norm and have another explanation. From 18,707 measurements of nester size (curve carapace length) for sea turtles spanning 30 years from Redang Island (Malaysia), where nearly all nesting individuals have been tagged, we show that the mean size was initially fairly stable and then decreased by 4.0 cm from 100.8 cm in 2005 to 96.8 cm in 2022, which likely translates to a change in mean mass from 120 to 105 kg. At the same time, nesting increased from around 300 to 2000 nests per year. Consistent with this finding of a size reduction in an expanding population, at 27 of 31 sites across the globe where changes in the mean size of nesting sea turtles have been assessed, mean size is decreasing, and the most marked decreases are at sites where population size is increasing most dramatically. Taken together, these focal and global findings suggest that an important driver of size reductions in sea turtles is an influx of small first-time nesters (neophytes) in expanding populations, and hence, size reductions are partially a consequence of successful sea turtle conservation measures and population recoveries. At the same time, the focal observations in Malaysia show that the mean size of neophytes has also been getting smaller over time: from 99.6 to 96.8 cm between 2005 and 2022, likely because of a change in foraging environments. While smaller turtles have lower reproductive output, this negative consequence of decreases in nester size will often be more than offset by increases in nesting numbers that are occurring widely.

Sea turtle hatchlings rely on their finite energy reserve to sustain embryonic development in underground nests and during the first few days of their post-hatch life, including nest escape, beach crossing, and swimming offshore. This study aimed to investigate if the grain size of the nest substrate has an impact on green sea turtle (Chelonia mydas) hatchlings’ energy usage during nest escape. About-to-hatch green sea turtle eggs were incubated in laboratory chambers filled with either coarse-grain sand (φ = 0.507 phi) or fine-grain sand (φ = 2.028) at a temperature of 28oC. Open-flow respirometry was used to measure the hatchlings’ oxygen consumption rate during nest escape, which was then converted to energy consumption values. Results showed that hatchling morphology, hatching success, emergence success, and synchronous emergence rate were not significantly different between the groups of hatchlings in coarse versus fine sand. Hatchlings that dug through coarse sand emerged significantly faster (168 ± 13.9 h) than those in fine sand (233.21 ± 12.6 h) (t (26) = –3.473, p = 0.002). Additionally, the hatchlings in coarse sand (310.55 ± 28.1 kJ) consumed significantly less energy than hatchlings in fine sand (474.85 ± 64.7 kJ) (t (17.739) = –2.328, p = 0.032). A difference in amount of energy reserve upon emergence was detected between coarse and fine sand groups. To improve hatchery management practices, relocating “doomed” clutches into coarse sand (φ = 0.507) could potentially maximise the hatchlings’ energy reserve.

Animals that hatch within a subterranean nest, such as turtle hatchlings, expend some of their limited energy reserves digging out through sand or soil to reach the surface. In sea turtles, this emergence process can take the hatchlings 3-7 days. However, we have a poor understanding of this process as it is difficult to observe what is occurring underground. Here, we utilize a novel method to characterize digging-out behaviour: affixing an accelerometer directly to newly hatched green turtles (Chelonia mydas) to record movement until nest emergence. Our data revealed that buried hatchlings maintained a head-up orientation but did not move in the expected left and right swaying motion associated with alternating limb crawling. Rather, they moved using dorsal-ventral heaving and pitching as if swimming vertically through the sand to the surface. Movement activity was irregular and brief, interspersed by many short periods of inactivity, mostly lasting less than 10 min. The first 24 h of head-up activity displayed no diel patterns, but the last 24 h prior to emergence involved more intense movement during night-time hours compared with daytime hours. Thus, our results add valuable new insight, and in some cases change previous assumptions, regarding the digging behaviours during the egg-to-emergence life stage in sea turtles.

Rising temperatures due to global warming over the last decades pose threats to marine biodiversity. Sea turtles are ectothermic species, and their embryonic development depends on nest conditions, particularly temperature. Here, we explore how increasing and extreme temperatures within the 558 nests can impact the hatching success of two sea turtle species, the green turtle (Chelonia mydas) and the loggerhead turtle (Caretta caretta), at two tropical locations, Cape Verde and Australia, and at temperate nesting sites, Turkey and Greece. Mean nest temperatures were higher for green turtles (30.84 °C) than for loggerhead turtles (29.42 °C) and significantly increased in all locations as the air temperature increased. However, nests from temperate locations, such as green turtles in Turkey and loggerhead turtles in Cape Verde, experienced higher temperatures than the nests in Australia and Greece, reaching lethal temperatures at extreme temperature peaks. Thus, temperate populations might be at risk as global warming continues because it is uncertain whether these higher latitudes can provide beach habitats cool enough for successful sea turtle nesting given the projected more frequent extreme temperatures in the future.

Deterioration of seagrass beds worldwide has raised concern about the future of dugongs because almost all aspects of their life history depend on availability of seagrass. Understanding their energy metabolism and consequently how much seagrass they need will inform protective conservation strategies for dugongs. This study determined resting metabolic rate (RMR) in five wild-caught adult dugongs by measuring oxygen consumption (V$$ \overset{\cdotp }{\mathrm{V}} $$O2). Measurement conditions met assumptions for RMR, except that dugongs were not postabsorptive, thus a postprandial (pp) allometric equation for herbivorous mammals of similar size was used to predict an expected RMRpp for dugongs of known mass. V$$ \overset{\cdotp }{\mathrm{V}} $$O2 was measured for 30 min in a metabolic tank after brief habituation. Dugongs' RMRpp was approximately half that predicted for their body mass but was higher than for manatees. Based on dugongs' RMRpp and considering plant caloric and water content, the daily minimum intake of fresh weight seagrass was 40-65 kg Halophila ovalis, or 20-40 kg Halodule spp. Greater seagrass intake would be required for growing and reproducing dugongs. Slow growth and protracted reproductive rates of dugongs are likely related to limitations in seagrass energy and nutrients. To ensure viability of this vulnerable species, it is critically important to conserve extensive healthy seagrass beds.

Sea turtles are vulnerable to climate change since their reproductive output is influenced by incubating temperatures, with warmer temperatures causing lower hatching success and increased feminization of embryos. Their ability to cope with projected increases in ambient temperatures will depend on their capacity to adapt to shifts in climatic regimes. Here, we assessed the extent to which phenological shifts could mitigate impacts from increases in ambient temperatures (from 1.5 to 3°C in air temperatures and from 1.4 to 2.3°C in sea surface temperatures by 2100 at our sites) on four species of sea turtles, under a "middle of the road" scenario (SSP2-4.5). Sand temperatures at sea turtle nesting sites are projected to increase from 0.58 to 4.17°C by 2100 and expected shifts in nesting of 26-43 days earlier will not be sufficient to maintain current incubation temperatures at 7 (29%) of our sites, hatching success rates at 10 (42%) of our sites, with current trends in hatchling sex ratio being able to be maintained at half of the sites. We also calculated the phenological shifts that would be required (both backward for an earlier shift in nesting and forward for a later shift) to keep up with present-day incubation temperatures, hatching success rates, and sex ratios. The required shifts backward in nesting for incubation temperatures ranged from -20 to -191 days, whereas the required shifts forward ranged from +54 to +180 days. However, for half of the sites, no matter the shift the median incubation temperature will always be warmer than the 75th percentile of current ranges. Given that phenological shifts will not be able to ameliorate predicted changes in temperature, hatching success and sex ratio at most sites, turtles may need to use other adaptive responses and/or there is the need to enhance sea turtle resilience to climate warming.

Global warming is increasing marine turtle nesting beach sand temperatures throughout the world. All marine turtles have temperature-dependent sex determination, with female hatchlings produced at warmer incubation temperatures. These warmer sand temperatures are causing a scarcity of male hatchlings at many nesting beaches. A range of mitigation strategies including shading and freshwater irrigation are being trialled at marine turtle nesting beaches around the world to address this issue. Because seawater is always abundant at marine turtle nesting beaches, we trialled a number of intense, one-off seawater irrigation experiments (equivalent to 100 and 200 mm rainfall) to test if male green turtle Chelonia mydas hatchling production could be increased without decreasing overall hatching success at Heron Island, southern Great Barrier Reef, Australia. We found that different combinations of seawater volume and temperature could produce a short-term drop in nest temperature by 2°C. When applied during the middle of embryonic development, these irrigation treatments could increase the proportion of male hatchlings compared to non-irrigated control nests, with less than a 10% decrease in hatching success. Hence, seawater irrigation has the potential to be a viable management strategy to increase the proportion of male marine turtle hatchlings at beaches that produce all, or nearly all, female hatchlings.

Projection models are being increasingly used to manage threatened taxa by estimating their responses to climate change. Sea turtles are particularly susceptible to climate change as they have temperature-dependent sex determination and increased sand temperatures on nesting beaches could result in the 'feminisation' of hatchling sex ratios for some populations. This study modelled likely long-term trends in sand temperatures and hatchling sex ratios at an equatorial nesting site for endangered green turtles (Chelonia mydas) and critically endangered hawksbill turtles (Eretmochelys imbricata). A total of 1078 days of sand temperature data were collected from 28 logger deployments at nest depth between 2018 and 2022 in Papua New Guinea (PNG). Long-term trends in sand temperature were generated from a model using air temperature as an environmental proxy. The influence of rainfall and seasonal variation on sand temperature was also investigated. Between 1960 and 2019, we estimated that sand temperature increased by similar to 0.6 degrees C and the average hatchling sex ratio was relatively balanced (46.2% female, SD = 10.7). No trends were observed in historical rainfall anomalies and projections indicated no further changes to rainfall until 2100. Therefore, the sex ratio models were unlikely to be influenced by changing rainfall patterns. A relatively balanced sex ratio such as this is starkly different to the extremely female-skewed hatchling sex ratio (>99% female) reported for another Coral Sea nesting site, Raine Island (similar to 850 km West). This PNG nesting site is likely rare in the global context, as it is less threatened by climate-induced feminisation. Although there is no current need for 'cooling' interventions, the mean projected sex ratios for 2020-2100 were estimated 76%-87% female, so future interventions may be required to increase male production. Our use of long-term sand temperature and rainfall trends has advanced our understanding of climate change impacts on sea turtles.

Sea turtle nesting beaches are experiencing increased sand temperatures as climate change progresses. In one major green turtle (Chelonia mydas) nesting beach in the northern Great Barrier Reef, over 99 percent of hatchlings are female. The effects of contaminants on sea turtle hatchling sex determination are not often explored. Liver samples were collected from green turtle hatchlings that were sacrificed for histological sex determination in a parallel study on the effects of sand cooling on sex ratios, and analysed for trace elements via acid digestion and organic contaminants via in vitro cytotoxicity bioassays. Chromium, antimony, barium, and cadmium have previously been demonstrated to be estrogenic, and concentrations of these elements were used to calculate three estrogenic indexes for each clutch: predicted relative estrogenic potency (PEEQA), the sum of percent trace elements above the median of all samples (TEOM), and the sum of percent estrogenic elements above the median of all samples (EstroEOM). Excluding an outlier clutch, cadmium, antimony, and EstroEOM had significant positive relationships with sex ratio deviation. Mean clutch cobalt, lead, antimony and barium, also had a significant positive relationship with clutch sex ratio. There was no relationship between in vitro cytotoxicity of liver extracts and sex ratio, however, 9% of hatchlings had organic contaminants high enough to suggest potential cellular damage. Contaminant effects on sex determination are likely to be caused by a mixture of contaminant interactions as well as temperature. Many trace elements detected in this study have also been linked to negative health effects on hatchlings in previous studies. Considering the risks of feminization due to climate change and potential contaminant effects on hatchling health and sex determination, future studies exploring contaminant effects on sea turtle hatchling sex determination are recommended.

The implications of logger accuracy and precision are rarely considered prior to their application in many ecological studies. We assessed the accuracy and precision of three temperature data loggers widely used in ecological studies (Hobo®, iButton® and TinyTag®). Accuracy was highest in TinyTags (95% of readings were within 0.23°C of the true temperature) and lowest in HOBOs and iButtons (95% of were readings within 0.43°C and 0.49°C of the true temperature, respectively). The precision (standard deviation of the repeat measurements) was greatest in TinyTags (0.04°C), followed by iButtons (0.17°C) and then HOBOs (0.22°C). As a case study, we then considered how modelled estimates of sea turtle hatchling sex ratios (derived from temperature), could vary as a function of logger accuracy. For example, at 29°C when the mean sex ratio derived was 0.47 female, the sex ratio estimate from a single logger could vary between 0.40 and 0.50 for TinyTags and 0.29 and 0.56 for both HOBOs and iButtons. Our results suggest that these temperature loggers can provide reliable descriptions of sand temperature if they are not over-interpreted. Logger accuracy must be considered in future ecological studies in which temperature thresholds are important.

Development rate of ectothermic animals varies with temperature. Here we use data derived from laboratory constant temperature incubation experiments to formulate development rate models that can be used to model embryonic development rate in sea turtle nests. We then use a novel method for detecting the time of hatching to measure the in situ incubation period of sea turtle clutches to test the accuracy of our models in predicting the incubation period from nest temperature traces. We found that all our models overestimated the incubation period. We hypothesize three possible explanations which are not mutually exclusive for the mismatch between our modeling and empirically measured in situ incubation period: (1) a difference in the way the incubation period is calculated in laboratory data and in our field nests, (2) inaccuracies in the assumptions made by our models at high incubation temperatures where there is no empirical laboratory data, and (3) a tendency for development rate in laboratory experiments to be progressively slower as temperature decreases compared with in situ incubation.

Rising sand temperatures resulting from climate warming may cause the ‘feminization’ of sea turtle populations, which have temperature-dependent sex determination. In July and October 2021, we conducted surveys using a drone (also referred to as an unmanned aerial vehicle or UAV) and shore-based observations to assess the operational sex ratio (OSR) (number of males and females in breeding condition) for green turtles ( Chelonia mydas ) in the southern Great Barrier Reef, Australia (23.44 °S, 151.92 °E). Using drone-imagery, the length:width (L:W) ratio of a turtle’s head was used to distinguish loggerhead turtles ( Caretta caretta ) from green turtles, and the L:W of the carapace was used to distinguish juveniles from adult-sized green turtles. The first breeding pair was observed in shore-based surveys on 14 September 2021 and the number of mating turtles then increased to a peak on 4 October, about 8 weeks before the peak in nesting. A total of 94 km of drone transects with associated video footage was analysed. In October, at the peak of the mating season, the ratio of adult turtles displaying breeding behaviours near the island was 0.51 female (95% CI ± 0.17), supporting previous conclusions that despite the female-biased (> 80%) hatchling sex ratio, this population likely has a fairly balanced OSR. These findings are likely explained by males breeding 2–3 times more frequently than females, which helps mitigate female-biased hatchling sex ratios. Assessing the OSR of populations with extreme female hatchling bias may help to inform whether intervention is needed to increase male hatchling production.

Abstract Context. Increasingly, ecological studies of sea turtles are measuring locomotion performance of newly emerged hatchlings in raceways and swimways under the assumption that locomotion performance measured in these structures reflects locomotion performance in nature, and that such measurements reflect the chance of a hatchling surviving dispersion from their natal beach. Aims. The aim was to test the assumption that an individual hatchling’s performance measured in artificial structures is correlated with the same individual’s performance in the natural environment (beach and sea), adding confidence that such measurements are an indirect indicator of dispersal ability during the first 24 h of post-nest life. Methods. Green turtle (Chelonia mydas) hatchlings that had just emerged from their nest had their crawling and swimming speeds measured in an on-beach raceway and swimway. The same hatchlings then had their beach crawling and sea swimming speed measured and the correlation between their performance in the artificial structures and natural crawls and swims calculated. Key results. An individual sea turtle hatchling’s locomotion performance in nature was correlated with its locomotion performance in raceways and swimways, but beach crawling was generally slower than raceway crawling, and sea swimming was generally faster than swimway swimming. We also found a weaker correlation between the raceway and beach crawling speeds than the sea and swimway swimming speeds. Conclusions. The measurement of sea turtle hatchling crawling speed and swimming speed in artificial structures correlated with the individual’s locomotion performance in nature, supporting the assumption that the locomotion performance measured in artificial structures reflects their relative locomotion performance in the natural environment. Implications. The measurement of sea turtle hatchlings locomotion performance in artificial structures can be used to indicate how variations in the nest microenvironment such as temperature and moisture affect a hatchling’s real-life locomotion performance, and thus reflect a hatchling’s dispersal ability during the first 24 h of post-nest life. Thus, sea turtle rookery managers can use this information to assess how their incubation management strategies affect hatchling locomotion performance, and consequently their likely offshore dispersal ability.

The Asian water monitor (Varanus salvator) is a large generalist predator and scavenger lizard. This species has a widespread distribution throughout South and Southeast Asia and is frequently encountered around the edges of urban settlements. Here, we present information on diet diversity and habitat utilisation of a population of Asian water monitors inhabiting the University of Malaysia Terengganu campus located on the east coast of mainland Malaysia. The stomach contents of 30 Asian water monitors were examined by stomach flushing, and 47.6% of stomach contents was mangrove crab, 26.2% was human waste and 26.2% was other natural foods consisting of fruits, fishes, leeches, snails, birds and insects. We then recorded the locations and habitats utilised by patrolling the campus area and found Asian water monitors preferred to use water and mangrove forest habitats that fringed and crisscrossed the campus. The broad diversity of stomach contents reflected food available at this location and indicates the opportunistic feeding habit of this species. Given that this species widely distributed in Southeast Asia, its broad diet diversity and habitat variations may promote the adaptation of Asian water monitor to different environments.

Spawn sea urchin embryos for immunofluorescence and vital dyes.

Raine Island, the world's largest green turtle nesting location, has low nest hatching success. The main causes of this low hatching success are thought to be nest destruction by subsequent nesting females, and inundation of nests during high tides and storm surges. But even nests that are protected from nest destruction and inundation appear to have relatively low hatching success, with most of the embryo mortality occurring early in incubation. Here, I compare hatching success and developmental phase of embryo death of protected `dry' nests from Raine Island (RI) with similar nests from Heron Island (HI), a nesting location previously reported as having high hatching success. Nests at both sites were sampled close to the peak time of nesting (December). Twenty-eight nests were sampled at RI and 14 nests at HI. Nest temperatures were cooler during the first week of incubation at HI (median 26.9 degrees C) than at RI (median 30.1 degrees C), but three-days-in-a-row maximum nest temperatures were higher at HI (median 36.0 degrees C) than at RI (median 33.5 degrees C). I found the hatching success of sampled nests at both locations was similar, similar to 70%, but most embryo death occurred early in incubation at RI (median 16.5%) compared to HI (median 3.8%), but late in incubation at HI (median 4.9%) compared to RI (median 0.2%).

In this lab, you will use immunofluroescence staining to visualize the wondrous cellular transformations that occur throughout sea urchin development. The goals of this module: 1. To learn about marine organisms at Marine Resources and some of their biology 2. Understand the steps of immunofluorescence and its relative advantages 3. Visualize embryos stained with antibodies and vital dyes with basic imaging techniques