Partitioning of PFAS to serum, tissues, eggs, and hatchlings of an Australian freshwater turtle

Turtles are a potential sentinel species of aquatic ecosystem health as they inhabit aquatic ecosystems, are long lived, and potentially have high exposure to anthropogenic chemicals via food and water. This study investigated per- and polyfluoroalkyl substances (PFAS) tissue partitioning in female Emydura macquarii macquarii turtle, and the maternal offloading of (PFAS) into eggs and then hatchlings as well as the accumulation of PFAS in male and female Emydura macquarii macquarii serum. Significantly higher levels of perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs) were measured in the male serum compared to the female turtle serum, whereas perfluoroalkane sulfonamides (FASAs) were significantly higher in the female turtle serum. Perfluorooctane sulfonate (PFOS) was the predominant PFAS in the turtles whereas PFHxA was the predominant PFAS found in the surrounding water. PFHxA was not reported in any turtle tissue or the serum. The short-chain PFSAs and FASAs appeared to be highly associated with blood; long-chain PFSAs and PFCAs were more likely to be associated with tissue. Half of the PFHxS and all the long-chain PFSAs and PFCAs reported in the yolks were transferred into the hatchlings (by mass), suggesting a potential intergenerational effect.

Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity

Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.

Patterns of nesting behaviour and nesting success for green turtles at Raine Island, Australia

To understand how turtles use the nesting habitat at Raine Island across a nesting season, and how the turtles respond to the restoration of the island’s dune systems, we identified 534 nesting events for 39 green turtles Chelonia mydas across 2 breeding seasons using data derived from satellite tags. Tracked turtles laid between 4 and 10 clutches of eggs. Patterns of nesting success varied between individuals, within and between seasons. Nesting success was higher in 2018-19 (57%) than 2017-18 (45%), and in both years, nesting success was lowest between October and early January (<50%). In 2017-18, increased rainfall in January corresponded with increased nesting success (>50%). The density of female turtles ashore was lower in 2018-19, and likely explains higher nesting success in 2018-19 because competition for nest space was lower. In 2017-18, females had more attempts per clutch, and the attempts were around 90 min longer. Consequently, energy required to lay a clutch of eggs in 2017-18 was significantly higher than in 2018-19, highlighting potential costs of lower nesting success rates on reproductive output. The area of beach re-profiled as an intervention in 2014 and 2017 was a nesting hotspot in 2017-18. However, in 2018-19, the area was not used to the same extent, and the nesting hotspot occurred on the north-eastern unaltered beach. Collectively, the tracking of turtles across the whole nesting season enabled us to assess overall beach use and nesting site fidelity of green turtles at Raine Island. Results will aid future planning and management of beach restoration activities at turtle nesting sites.

A multi-element screening method to identify metal targets for blood biomonitoring in green sea turtles (Chelonia mydas)

Biomonitoring of blood is commonly used to identify and quantify occupational or environmental exposure to chemical contaminants. Increasingly, this technique has been applied to wildlife contaminant monitoring, including for green turtles, allowing for the non-lethal evaluation of chemical exposure in their nearshore environment. The sources, composition, bioavailability and toxicity of metals in the marine environment are, however, often unknown and influenced by numerous biotic and abiotic factors. These factors can vary considerably across time and space making the selection of the most informative elements for biomonitoring challenging. This study aimed to validate an ICP-MS multi-element screening method for green turtle blood in order to identify and facilitate prioritisation of target metals for subsequent fully quantitative analysis. Multi-element screening provided semiquantitative results for 70 elements, 28 of which were also determined through fully quantitative analysis. Of the 28 comparable elements, 23 of the semiquantitative results had an accuracy between 67% and 112% relative to the fully quantified values. In lieu of any available turtle certified reference materials (CRMs), we evaluated the use of human blood CRMs as a matrix surrogate for quality control, and compared two commonly used sample preparation methods for matrix related effects. The results demonstrate that human blood provides an appropriate matrix for use as a quality control material in the fully quantitative analysis of metals in turtle blood. An example for the application of this screening method is provided by comparing screening results from blood of green turtles foraging in an urban and rural region in Queensland, Australia. Potential targets for future metal biomonitoring in these regions were identified by this approach.

Temporal changes in artificial light exposure of marine turtle nesting areas

Artificial light at night poses a significant threat to multiple taxa across the globe. In coastal regions, artificial lighting close to marine turtle nesting beaches is disruptive to their breeding success. Prioritizing effective management of light pollution requires an understanding of how the light exposure of nesting areas changes over time in response to changing temporal and spatial distributions of coastal development. We analyzed multitemporal, satellite night-light data, in combination with linear mixed model analysis, to determine broadscale changes in artificial light exposure at Australian marine turtle nesting areas between 1993 and 2010. We found seven marine turtle management units (MU), from five species, have experienced significant increases in light exposure over time, with flatback turtles nesting in east Australia experiencing the fastest increases. The remaining 12 MUs showed no significant change in light exposure. Unchanging MUs included those previously identified as having high exposure to light pollution (located in western Australia and southern Queensland), indicating that turtles in these areas have been potentially exposed to high light levels since at least the early nineties. At a finer geographic scale (within-MU), nine MUs contained nesting areas with significant increases in light exposure. These nesting areas predominantly occurred close to heavily industrialized coastal areas, thus emphasizing the importance of rigorous light management in industry. Within all MUs, nesting areas existed where light levels were extremely low and/or had not significantly increased since 1993. With continued coastal development, nesting females may shift to these darker/unchanging 'buffer' areas in the future. This is valuable information that informs our understanding of the capacity and resilience of marine turtles faced with coastal development: an understanding that is essential for effective marine turtle conservation.

Influence of industrial light pollution on the sea-finding behaviour of flatback turtle hatchlings

Context Numerous studies show that artificial light disrupts the sea-finding ability of marine turtle hatchlings. Yet very little has been published regarding sea-finding for flatback turtles. Given the current industrialisation of Australia’s coastline, and the large potential for disruption posed by industrial light, this study is a timely investigation into sea-finding behaviour of flatback turtle hatchlings. Aims We investigate sea-finding by flatback turtle hatchlings in relation to ambient light present in areas of planned or ongoing industrial development, and evaluate the fan and arena-based methods that are frequently used for quantifying hatchling dispersion. Methods Using a combination of methods, we assessed the angular range and directional preference of sea-finding hatchlings at two key flatback turtle rookeries, Peak and Curtis Islands, during January–February 2012 and 2013, and at Curtis Island in January 2014. Relative light levels at each site were measured using an Optec SSP-3 stellar photometer, and moon phase, moon stage and cloud cover were also recorded. Key results We found no evidence of impaired hatchling orientation, and observed very low levels of light at Peak Island. However, at Curtis Island, hatchlings displayed reduced sea-finding ability, with light horizons from the direction of nearby industry significantly brighter than from other directions. The sea-finding disruption observed at Curtis Island was less pronounced in the presence of moonlight. Conclusions The reduced sea-finding ability of Curtis Island hatchlings was likely due to both altered light horizons from nearby industry, as well as beach topography. Both methods of assessing hatchling orientation have benefits and limitations. We suggest that fan-based methods, combined with strategically placed arenas, would provide the best data for accurately assessing hatchling sea-finding. Implications Sky glow produced by large-scale industrial development appears detrimental to sea-finding by flatback turtle hatchlings. As development continues around Australia’s coastline, we strongly recommend continued monitoring of lighting impacts at adjacent turtle nesting beaches. We also advise rigorous management of industrial lighting, which considers cumulative light levels in regions of multiple light producers, as well as moon phase, moon-stage, cloud cover and time of hatchling emergence. All these factors affect the likelihood of disrupted hatchling sea-finding behaviour at nesting beaches exposed to artificial light-glow, industrial or otherwise.

Ocean-finding in marine turtles: the importance of low horizon elevation as an orientation cue

Sea finding behaviour in hatchling sea turtles is widely believed to be guided by orientation towards the brightest horizon and away from high silhouettes. We propose that the horizon profile at the lowest angle of elevation is a more important cue for ocean finding than light intensity. Examples of hatchling orientation occurring at natural nest sites, at preselected beach release sites, and within a walled wooden arena under various conditions in the field, are presented. We conclude that hatchlings orient as follows: (1) Hatchlings move towards the horizon line at the lowest angle of elevation; (2) Hatchlings move away from high silhouettes, in a direction that remains close to the horizon line at the lowest angle of elevation; (3) Should a conflict exist regarding the direction of lowest horizon elevation, hatchlings move towards the brightest lowest horizon. This refinement to current theory explains numerous instances of natural non-ocean-finding behaviour in marine turtles, which occur both by day and by night, and in the absence of artificial lighting. We propose that the disruption caused to hatchling orientation by artificial lighting close to nesting beaches occurs because bright lights mask the horizon line as a cue by making it impossible to discern, causing the hatchlings to move towards the only visible “horizon” — the artificial lights. Consequently, we recommend that managers of sea turtle rookeries where turtles have an ocean-finding problem should manipulate the beach profile to ensure the direction of the ocean matches the lowest angle of elevation, in combination with light reduction strategies — as the most effective means of preventing disrupted orientation.

Incorporating marine turtle habitats into the marine protected area design for the Great Barrier Reef Marine Park, Queensland, Australia

Marine turtle habitats were considered in the design of the new zoning network for the Great Barrier Reef Marine Park as part of the Representative Areas Programme. One of the specific design guidelines developed was the incorporation of marine turtle inter-nesting and foraging habitats into the overall network of no-take areas. The guideline was refined further for individual nesting and foraging sites to incorporate all very high priority nesting sites and to incorporate 20% of each identified foraging site, respectively. Marine turtle inter-nesting habitat increased in no-take area protection from 781 km2 to 1 886 km2 (23.4% to 56.5% of all identified sites); marine turtle foraging habitat increased in no-take area protection from 3 063 km2 to 12 490 km2 (7.1% to 29.1% of all identified sites). Although the nesting and foraging principles were not achieved in total for all identified marine turtle sites, overall the level of protection afforded by the Great Barrier Reef Marine Park Zoning Plan 2003 increased for nearly all marine turtle sites identified. Additionally, other activities (e.g. water quality, fisheries, traditional use of marine resources) occurring in the Great Barrier Reef Marine Park that may impact upon marine turtles are being addressed via other mechanisms.

Reproduction in shark-attacked sea turtles is supported by stress-reduction mechanisms

Vertebrates exhibit varied behavioural and physiological tactics to promote reproductive success. We examined mechanisms that could enable female loggerhead turtles to undertake nesting activities and maintain seasonal reproduction despite recent shark injuries of varying severity. We proposed that endocrinal mechanisms that regulate both a turtle's stress response and reproductive ability are modified to promote successful and continued reproduction. Irrespective of the degree of injury, females did not exhibit increased levels of the stress hormone corticosterone, nor decreased levels of the reproductive steroid testosterone; hormone responses consistent with stress. When exposed to a capture stressor, females with shark injury did not exhibit any greater corticosterone response than controls. In addition, breeding females showed a reduced corticosterone stress response compared to non-breeding females. Reduced endocrinal responses following shark injury, and during breeding in general may, in part, enable females to maintain behavioural and physiological commitment to reproduction.

Plasma steroid profiles in nesting loggerhead turtles (Caretta caretta) in Queensland, Australia: relationship to nesting episode and season

Plasma levels of four hormones-progesterone (P), testosterone (T), estradiol 17-beta (E2), and corticosterone (B)-were measured in samples taken from nesting female loggerhead turtles (Caretta caretta) by using specific radioimmunoassays. Samples were taken in an early, middle, or late period during the summer nesting season from females at first, second, third, or > fourth nesting episodes, defined as successive within-season nesting events, at Mon Repos Beach, Queensland, Australia. Data on individual patterns of nesting, collected over the past 20 years by the Queensland Turtle Research Project, and the seasonal nesting data, were analyzed with respect to influences on hormonal profiles. Circulating levels of E2 were mostly undetectable, suggesting either that this estrogen is not produced at this time of nesting, or that, perhaps, another estrogen may be present that is not detected by the specific radioimmunoassay. P, T, and B profiles in the nesting females were associated with the individual turtles' progression through successive nesting episodes, with a marked decline in all three hormones by the last (> 4) nesting episode of the season. Nesting episode accounted for significant changes that were related to season, in that nesting episode and season were significantly correlated. These patterns were observed in the population, when singly sampled at each time period or nesting episode, and in individual females sampled repeatedly over time. Moreover, T and B were highly and significantly correlated in females at all nesting episodes and time periods, and in the singly and repeatedly sampled females. The magnitude of change in T and B over time was also highly and significantly correlated in repeatedly sampled females. Together these results suggest the hypothesis that T and B interact over the period of successive nesting and may be involved in reproductive functions such as the mobilization of reserves for egg production in C. caretta.

Serum gonadotropins and gonadal steroids associated with ovulation and egg production in sea turtles

Changes in serum concentrations of gonadotropins and gonadal steroids during the periovulatory period were monitored in green, Chelonia mydas, and loggerhead, Caretta caretta, sea turtles. Turtles were from natural populations that nest on a coral island on the Great Barrier Reef. After nesting, each turtle was transferred to a holding tank and held for a maximum of 8 days. A time series of blood samples was obtained from each of five sea turtles (three C. mydas and two C. caretta) starting immediately after nesting and then at approximately 12-hr intervals until the time of release. Prior to release back into the ocean, each turtle was examined by laparoscopy to verify that ovulation had occurred. Serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone (PRO), and testosterone (T) in both species exhibited significant changes during this period. Surges of FSH, LH, and PRO were evident within approximately 20 to 50 hr after each turtle had nested. The significant change in FSH concentration during the periovulatory period is the first such report for a reptile. Coincident with maximal concentrations of FSH, LH, and PRO was a decline in T concentrations in both species. Estradiol-17 beta concentrations were near or below assay sensitivity in the C. mydas, whereas those in the C. caretta were detectable but exhibited no significant changes. The dynamic changes in FSH, LH, PRO, and T concentrations are consistent with the hypothesis that these hormones facilitate specific physiological events during ovulation and egg production.