IntroductionIdentifying critical habitats for marine turtles and connectivity between genetic stocks and the foraging grounds they use is a conservation priority worldwide. Green turtles (Chelonia mydas) are impacted by a wide range of anthropogenic threats that can vary by geographic region and the ontogenetic stage of the individual. In Australia, the strengthening of the East Australian Current due to climate change is increasing ocean temperatures, particularly in southern New South Wales (NSW), which is having large-scale impacts on the distribution and abundance of marine resources. Green turtles are frequently observed in temperate southern NSW waters, but our knowledge of their habitat use, migration patterns and the impact of threatening processes is limited.MethodsTo assess the origins of green turtles from foraging grounds in southeastern Australia, samples were obtained from green turtles of all size classes (post-hatchlings to adults) that had stranded along an ~870 km expanse of the NSW coast and Lord Howe Island between 1997 and 2021. Mitochondrial DNA control region sequences for 283 individuals were compared to 25 potential source genetic stocks in the Indo-Pacific using mixed-stock analysis.ResultsA total of 26 haplotypes were identified in NSW, of which 14 had been previously observed at a rookery, eight had been identified previously, but not at a rookery (i.e. orphan haplotypes), and four were previously undescribed. Mixed-stock analysis revealed that NSW waters support multiple genetic stocks but are dominated by those of the southern Great Barrier Reef and New Caledonia genetic stocks. A small proportion of green turtles originated from more distant stocks in the Indo-Pacific region.DiscussionUnderstanding the connectivity between green turtle rookeries and foraging grounds provides an opportunity to assess the impact of anthropogenic threats to turtle stocks, and in turn, prioritize management actions for the conservation of green turtles across regional, national and international jurisdictions.

Metal and organic pollutants are prominent marine contaminants that disperse widely throughout the environment. Some contaminants biomagnify, leaving long-lived apex predators such as cetaceans at risk of toxicity. Various tissues collected post-mortem from 16 Ziphiidae individuals that stranded on the New South Wales (NSW) coast, Australia, over ∼15 years were investigated for 16 metals/metalloids and 33 organic contaminants. Polychlorinated biphenyls (PCBs) and Dichlorodiphenyltrichloroethanes (DDTs) were commonly detected in blubber and liver tissues. Mercury, cadmium and silver exceeded reported toxicity thresholds in several individuals. The liver tissue of a Mesoplodon layardii specimen had the highest mercury (386 mg/kg dry weight). Liver tissue of a Mesoplodon grayi specimen had the highest silver concentration (19.7 mg/kg dry weight), and the highest cadmium concentration was in Ziphius cavirostris kidney (478 mg/kg dry weight). This study provides important new information for rare Ziphiidae species globally.

The wave-impacted waters off exposed sandy beaches support marine megafauna, including dolphins, whales, sharks, rays and turtles. To characterise variation in megafaunal assemblages in this challenging habitat, we used drone-based remote sensing to survey marine megafauna off 23 beaches along 1050 km of the New South Wales (NSW, Australia) coast from 2017 to 2020. The surveys occurred from September to May and included 17,085 drone flights, with megafaunal abundances standardised by flight hours. In total, we identified 3838 individual animals from 16 taxa, although no megafauna was observed off 5 of the 23 beaches surveyed. Bottlenose dolphins were the most commonly sighted taxa and accounted for 82.3% of total megafaunal abundance. Cownose (6.7%) and eagle (3.4%) rays were the next most abundant taxa, with potentially dangerous sharks being rarely sighted (<1% of total megafauna). The megafaunal assemblages off wave-exposed beaches in northern NSW significantly differed from those in the central region, whereas the assemblages off the central region and southern NSW did not differ significantly. Wave exposure and water temperature were the best predictors of megafaunal assemblage structure. The richness of marine megafauna off ocean beaches was significantly greater in northern than southern NSW, and turtles were only observed off beaches in the northern region. However, variation in megafaunal richness, as well as the abundances of total megafauna, dolphins, rays, sharks and turtles were not significantly explained by water temperature, wave height, distance to estuary, or proximity to the nearest reef. Overall, drone-based surveys determined that megafaunal assemblages off wave-exposed beaches are characterised by sparse individuals or small groups of sharks, turtles and rays, punctuated by occasional large aggregations of dolphins, cownose rays and schooling sharks. The exception to this pattern was bottlenose dolphins, which routinely patrolled some beaches in northern NSW.

Sea turtles are listed in threatened categories at national and international levels. Hundreds of sick and injured turtles are admitted to rehabilitation clinics annually, where recovery and release are important aspects of their conservation and management. There is considerable interest in establishing biochemical markers to gauge the health of sea turtles, and as diagnostic tools to facilitate informed decision-making about overall care and specific treatment needs during rehabilitation. We applied untargeted metabolomics to monitor the health of 28 green turtles (Chelonia mydas) admitted to a rehabilitation clinic in eastern Australia between October 2018 and April 2019. Malnutrition and ketosis were identified as major physiological manifestations in sea turtles entering rehabilitation. Specifically, decreased branch-chain (leucine, isoleucine and valine) and aromatic amino acids (tyrosine, phenylalanine and tryptophan) were observed at admission, along with increases in the ketogenic metabolite 3-hydroxybutyric acid and metabolites associated with peroxisomal disorders (pipecolic acid and beta-alanine). Receiver Operating Characteristic (ROC) analysis comparing successfully rehabilitated animals with those that died identified a suite of metabolites that were predictive of mortality. Results suggest that, regardless the source of injury or illness, a major cause of sea turtle mortality during rehabilitation relates to severe malnutrition that ultimately manifests as sepsis-induced metabolic failure. This showcases the strength of metabolomics for monitoring sea turtle health and informing care and management during rehabilitation. More broadly, this serves as a compelling case-study highlighting that advanced molecular analytical techniques are well positioned to play an important role in various aspects of veterinary medicine and conservation science.

This study investigated the influence of exercise and fasting state on haematologic and biochemical parameters in juvenile green turtles (Chelonia mydas). Animals were divided into two groups; one group was fasted for 72 h and one group was fed 1 h prior to exercise. Exercise was induced by repeated righting reflexes and blood values were measured prior to and post-exercise. Prior to exercise, fasted animals showed significantly decreased levels of urea, pH, PVCO2 and HCO3- and significant increases in Cl- and PVO2 compared to fed animals and fasted animals had significantly poorer exercise performance. Following exercise both fasted and fed animals had significant increases in Na+, K+, Cl-, PVCO2, PVO2, urea and lactate and significant decreases in pH and HCO3-. The magnitude of increase in lactate levels was significantly less in fasted animals. Prior to exercise, a significant correlation was calculated in fasted animals between pH and HCO3-. Following exercise, significant correlations were calculated in fed animals between pH and HCO3-, PVCO2 and lactate, and between pH and HCO3- in fasted animals. These results show that analytical method, fasting state and the physiologic changes induced during the intense exercise can affect haematologic and biochemical analytes and these factors should be considered when interpreting results from health assessment of wild animals.

An epizootic of coccidiosis in free-ranging green turtles (Chelonia mydas) occurred in Australia in 1991 and the parasites were thought to be Caryospora cheloniae. Recurring outbreaks over an increased geographic range followed. We used medical records and temporal and spatial data of turtles diagnosed with coccidiosis between 1991 and 2014 to characterize the disease and factors associated with outbreaks. Most atkcted animals were subadults or older. Neurologic signs with intralesional cerebral coccidia were observed. Coccidia associated with inflammation and necrosis were predominantly found in the intestine, brain, kidney, and thyroid. Cases occurred in the spring and summer. Three major outbreaks (1991, 2002, and 2014) were concentrated in Port Stephens, New South Wales (NSW) and Moreton Bay, Queensland, but cases occurred as far south as Sydney, NSW. Coccidiosis cases were more likely during, or 1 mo prior to, El Nino-like events. Molecular characterization of the 18S rRNA locus of coccidia from tissues of 10 green turtles collected in 2002 and 2004 in Port Stevens and Sydney imply that they were Schellackia-like organisms. Two genotypes were identified. The Genotype 3 sequence was most common (in eight of 10 turtles), with 98.8% similarity to the 18S sequence of Schellackia orientalis. The Genotype 4 sequence was less common (in two of 10 turtles) with 99.7% similarity to the 18S sequence of the most common genotype (Genotype 1) detected in turtles from the 2014 Moreton Bay outbreak. Our study will help with the identification and management of future outbreaks and provide tools for identification of additional disease patterns in green turtles.

Post-hatchling green turtles were subject to varied fasting regimes followed by a fitness assessment. Blood was collected prior to this assessment and biochemical changes indicated that short-term fasting induced a catabolic state, but did not compromise exercise output. Facilities holding these animals should consider this when designing pre-release protocols.

Climate change can affect marine and estuarine fish via alterations to their distributions, abundances, sizes, physiology and ecological interactions, threatening the provision of ecosystem goods and services. While we have an emerging understanding of such ecological impacts to fish, we know little about the potential influence of climate change on the provision of nutritional seafood to sustain human populations. In particular, the quantity, quality and/or taste of seafood may be altered by future environmental changes with implications for the economic viability of fisheries. In an orthogonal mesocosm experiment, we tested the influence of near-future ocean warming and acidification on the growth, health and seafood quality of a recreationally and commercially important fish, yellowfin bream (Acanthopagrus australis). The growth of yellowfin bream significantly increased under near-future temperature conditions (but not acidification), with little change in health (blood glucose and haematocrit) or tissue biochemistry and nutritional properties (fatty acids, lipids, macro- and micronutrients, moisture, ash and total N). Yellowfin bream appear to be highly resilient to predicted near-future ocean climate change, which might be facilitated by their wide spatio-temporal distribution across habitats and broad diet. Moreover, an increase in growth, but little change in tissue quality, suggests that near-future ocean conditions will benefit fisheries and fishers that target yellowfin bream. The data reiterate the inherent resilience of yellowfin bream as an evolutionary consequence of their euryhaline status in often environmentally challenging habitats and imply their sustainable and viable fisheries into the future. We contend that widely distributed species that span large geographic areas and habitats can be "climate winners" by being resilient to the negative direct impacts of near-future oceanic and estuarine climate change.

To improve understanding of pathophysiologic processes occurring in green sea turtles ( Chelonia mydas) stranded along the east coast of Australia, we retrospectively examined the hematologic and biochemical blood parameters of 127 green turtles admitted to 2 rehabilitation facilities, Dolphin Marine Magic (DMM) and Taronga Zoo (TZ), between 2002 and 2016. The predominant size class presented was small immature animals (SIM), comprising 88% and 69% of admissions to DMM and TZ, respectively. Significant differences in blood profiles were noted between facility, size, and outcome. Elevated levels of aspartate aminotransferase (AST) and heterophils were poor prognostic indicators in animals from TZ, but not DMM. SIM animals at both institutions had lower protein levels than large older (LO) animals. SIM animals at DMM also had lower hematocrit and monocyte concentration; SIM animals at TZ had lower heterophil counts. Urea was measured for 27 SIM animals from TZ, but the urea-to-uric acid ratio was not prognostically useful. Strong correlations were seen between AST and glutamate dehydrogenase (GDH; r = 0.68) and uric acid and bile acids ( r = 0.72) in the 45 SIM animals from DMM in which additional analytes were measured. χ2 contingency tests showed that the most recently published reference intervals were not prognostically useful. A paired t-test showed that protein levels rose and heterophil numbers fell in the 15 SIM animals from TZ during the rehabilitation process. Our results indicate that further work is required to identify reliable prognostic biomarkers for green turtles.