ISTS Symposium43 Program/Agenda

INTRODUCTION: The health status of critically endangered hawksbill sea turtles from the Indian Ocean area is largely unknown as few studies have been performed on this population. Insights into the health status of this species can inform local conservation measures that are not available by other monitoring and assessment means. The Republic of Maldives is home to a resident juvenile hawksbill foraging population with over 5,000 individuals identified. METHODS: We evaluated clinical indices of health in wild-caught juvenile hawksbill sea turtles (n=68) from eight atolls in the north central (NC) and south central (SC) regions of the Republic of the Maldives in 2023-24 in order to 1) establish clinical reference intervals for plasma biochemical and hematological analytes, 2) perform morphometric, physical, cardiopulmonary, and neurological examinations, 3) assess anatomically available structures by ultrasound study, 4) collect colonic and cloacal samples for gut microbial evaluation, and 5) determine sex by ultrasound. All work was subjected to independent animal welfare review. Blood analytes included Complete Blood Counts with manual differentiation, Packed Cell Volume, Total Solids, Glucose, Symmetric Dimethylarginine, Creatinine, Blood Urea Nitrogen, Uric Acid, Phosphorus, Calcium, Total Protein, Albumin, Globulin, Albumin:Globulin ratio, Alkaline Phosphatase, Aspartate Aminotransferase, Gamma-Glutamyl Transferase, Beta Hydroxybutyrate, Total Bilirubin, Cholesterol, Amylase, and Lipase. Full physical examinations were performed on each animal, including neurological and cardiopulmonary examination by ultrasound. Further ultrasound examinations were performed using pre-femoral and axillary access to evaluate all available organ systems. Samples were collected from the cloaca and distal colon using a specialized technique validated for this project. Gut samples were stored for subsequent microbial analysis. All animals were returned to the reefs without incident. RESULTS: Clinical biochemical analytes revealed hyperuricemia in animals from all regions. Hematological evaluation revealed marked increases in the SC atolls in the granulocytic lines (heterophils and eosinophils) with accompanying mild to moderate toxicities compared to the NC region. Ultrasound studies revealed evidence of mild to moderate enteric disease in 8.3% (3/36) in the NC atolls and 27.6% (8/29) in the SC atolls, and 13.8% (4/29) pulmonary disease in the SC atolls compared with none in the NC region. Sex determination by ultrasound revealed 9.3% male in the NC region and 37.9% male in the SC region. Body Condition Index (BCI) was 0.98 ± 0.11 in the NC region and 1.1 ± 0.22 in the SC region. Gut microbiome data are pending evaluation. CONCLUSIONS: Physiologic stressors and clinical evidence of renal, enteric and pulmonary disease were evident in both regions, but more pronounced in the SC region, which may reflect foraging ground disturbances from development and benthic ecosystem deterioration in this area. More males were present in the SC region than the NC, but this is likely a sampling bias. Interestingly, BCI did not correlate with health status, which has implications for the reliability of this morphometric measurement of fitness. This represents the first comprehensive health assessment of a population of critically endangered hawksbill sea turtles in the northwest Indian Ocean.

Sea turtles are exposed to, and accumulate, contaminants such as trace elements and organic chemicals (e.g. industrial chemicals, pesticides, pharmaceuticals) that can have negative implications for health. These contaminants enter the environment through a variety of urban, agricultural and industrial sources, which means that chemical exposure can change over time. However, the majority of toxicological studies only include one timepoint, which provides only a snapshot of chemical exposure. A long-term monitoring project carried out in Port Curtis, Australia, one of Australia’s largest shipping ports, has offered the unique opportunity for temporal analysis of contaminants in the green turtle population foraging within the port. Since 2016, Trace elements have been assessed chemical analysis and organic contaminants have been assessed using novel, cell-based techniques recently developed for sea turtles. Cell-based techniques can be used to assess the effects of environmentally relevant mixtures and concentrations of organic contaminants to which turtles are exposed by extracting contaminants from turtle blood and testing the toxicity of extracts on sea turtle cells. Trace elements such as Mn, Co, Zn, and Mo showed significant decreases in concentrations from 2016. Se and Cd exhibited significant increases in concentration between 2016 and 2021, followed by a decrease in 2022. Organic contaminants have also demonstrated significant temporal changes, remaining relatively stable until 2019 where there was a significant increase in exposure. Exposure levels returned to pre-2019 levels in 2021, then increased again in 2022. These results highlight the importance of including temporal aspects in experimental design for toxicology studies to better identify exposure baselines, and changes to exposure that have the potential to impact turtle health.

Loggerhead sea turtles (Caretta caretta) are listed as endangered under the Endangered Species Act and on the IUCN Red List. Climate change, particularly elevated temperatures, poses a significant threat to this species by negatively impacting their survival both in the ocean and on beaches. While previous work demonstrated that increased incubation temperatures adversely affect hatchling health, the possible long-term impacts on neonatal sea turtle health remain unclear. To begin to fill this large knowledge gap, we investigated the relationship between incubation temperatures and key blood analytes in neonatal loggerhead sea turtles (i.e., 4-5 weeks of age). Blood samples were collected from 114 neonates across 12 nests located in Boca Raton and Juno Beach, Florida. Key blood analytes (i.e., packed cell volume (PCV), total protein (TP), agarose gel electrophoresis (AGE), and capillary zone electrophoresis) were analyzed and compared to incubation temperatures. We found that neonates that incubated at higher temperatures had significantly higher PCV, and lower TP, albumin, beta-1, beta-2, and gamma globulins. The blood analyte shifts observed suggest that neonates that incubated in higher temperatures may be suffering from dehydration, malnutrition, and or immunodeficiency at 4-5 weeks of age. Prolonged suboptimal physiologic states such as these may negatively impact overall fitness and survival of a neonate in the wild. These data provide initial information to begin assessing the long-term negative impact of increasing incubations on neonatal health and possibly elucidate a cause for decreased survival in hatchlings incubated at higher temperatures. Ultimately, these findings can be useful for developing management strategies to mitigate the effects of elevated incubation temperatures in nature.

Sea turtles have long been affected by the changing environment. Fibropapillomatosis (FP) is a tumor-causing herpes virus primarily affecting green sea turtles.The main cause of FP is Chelonid herpesvirus 5, however, the pathophysiology is not fully understood. Some chemicals and biotoxins may encourage the growth of the virus. Past research has identified a correlation between the presence of sea turtles with FP and polluted/unhealthy coastal environments. Populations of sea turtles have been documented in St. Augustine, Florida in the Western Atlantic Ocean since 2020. Over this period, tumor prevalence has been noted as well. We aimed to calculate the amount of sea turtles with noticeable signs of FP to determine the prevalence of the virus in the St. Augustine population. Two marinas in St. Augustine, Florida were walked once a week and videos were taken of sea turtles using a GoPro 12. Using the unique patterns on their heads, sea turtles were identified using the Internet of Turtles software. Additionally, FP tumors were recorded on individual turtles. In conjunction with the University of Florida’s Sea Turtle Hospital at Whitney Lab and the Volusia Marine Science Center, we were able to track and document incidences of individual sea turtles before and after hospital visits. To date, we have identified 797 total individuals: 338 hospital patients and 459 wild sea turtles. Of those, 11 sea turtles have been seen in the wild that were also patients at the Sea Turtle Hospital at Whitney Lab. None of our identified sea turtles have been patients at Volusia Marine Science Center. These data suggest that there is a much larger population of green sea turtles in this area than our previous research shows. We may have been underestimating tumor prevalence by only observing sea turtle’s dorsal side, before utilizing GoPros to examine their full body. Preliminary results show that FP tumor load on St. Augustine's sea turtle population is higher than thought from dorsal observations alone. To date, 120 minutes have been recorded of wild sea turtles. Videos are being analyzed for tumor load on the St. Augustine sea turtle population and early results indicate tumors are more common on the ventral side of the turtles. It is crucial to understand the cause and effects of FP on sea turtles to further conservation efforts of the endangered keystone species.

Fibropapillomatosis (FP) is a globally distributed tumour-forming disease of marine turtles thought to be caused by chelonid alphaherpesvirus 5 (ChHV5). In Australia, reports of this disease have typically limited to incidental data. More recently, efforts increased to better characterise the spatial distribution of this disease and the associated viral variants along the coast of the eastern state of Queensland. Consistent with studies from other regions, the results of the Queensland studies showed that prevalence varies between sites and years, with juvenile green turtles (Chelonia mydas) being the most frequently affected by the disease. The viral variants were similarly consistent with other regions, clustering geographically and supporting the theory that the virus is likely transmitted horizontally at foraging grounds. However, the distribution of this disease and variants in other Australian states and territories has not yet been assessed.

Western Australia hosts six of the seven species of marine turtle. This state has the longest coastline of all Australian states and territories, posing significant challenges to the monitoring of marine turtles. Though long-term monitoring has been conducted at several sites (both nesting and foraging) in Western Australia, reports of FP in this region are limited. Tumour samples from two nesting loggerhead (Caretta caretta) turtles were collected and analysed alongside the Queensland samples in 2017. The viral variants obtained from these samples clustered with others from northern Queensland. Opportunities to collect additional samples have been scarce.

Through a targeted project aimed at better understanding the health and disease status of marine turtles in Western Australia, FP tumour samples from four (n=4) juvenile green turtles and one olive ridley turtle (Lepidochelys olivacea; n=1) were archived for analysis. These samples were collected from a relatively wide geographic scope that included Rottnest Island, Roebuck Bay and Shark Bay. An additional 17 samples were collected from the Cocos Keeling Islands, a remote territory, 2600 km of the WA coast. To establish the viral variant associated with each sample, extracted DNA was then subjected to a validated PCR assay. The resulting DNA sequences were utilised to generate a phylogenetic tree that compared the Western Australian samples with published sequences from Australian and international locations. The results of the phylogenetic analysis highlighted that the Western Australian samples cluster with either the North Queensland cluster or the earlier sequences obtained from the nesting loggerheads.

The similarity in viral variant sequences observed, despite the vast distance separating these study sites, warrants further investigation regarding habitat connectivity. Continued efforts are needed to better understand this distribution and elucidate why, given the similarities in viral variants, disease prevalence still appears to be relatively low.

Sewage discharge contributes to the nutrient-rich environment of Guanabara Bay (GB), located on the southeast coast of Brazil, in Rio de Janeiro. Green turtles serve as valuable marine bioindicators because their coastal foraging habits, long lifespan, and transoceanic migrations make them sensitive to environmental changes. Guanabara Bay, Brazil's second-largest bay, is heavily impacted by urbanization, with industries, residential areas, and agricultural activities contributing significant waste to its waters. Despite significant pollution, the bay remains ecologically diverse and provides a critical feeding ground for green turtles. However, the full extent of anthropogenic impacts and potential pathogens on the bay's ecosystem and its green turtle population remains unclear. To address this gap, we investigated the health status of green turtles feeding in Guanabara Bay. Our study focused on the presence of antibiotic-resistant bacteria and fibropapilloma (FP) tumors, we also evaluated the turtles’ body condition. Green sea turtles were intentionally captured using fishing nets, cloacal samples were collected with sterile swabs. Samples were preserved in DNA stabilization medium and rich culture medium for metagenomic and microbiological analyses. Metagenomic and cultured metagenomes (culturomes) analyses were carried out and the generated sequences were analyzed for taxonomy and resistance genes. Of the 107 turtles analyzed, 61% (n = 65) showed signs of fibropapillomatosis (FP). FP tumors were more common in turtles with a curved carapace length (CCL) of 40–65 cm (54.2%, n = 58) and an average to low body condition index (BCI: 1.11 ± 0.09). Enterobacterales was the most prevalent bacterial order (83.3%), with Citrobacter freundii emerging as the most common tetracycline-resistant pathogen. These findings indicate significant contamination from anthropogenic sources in the bay, as evidenced by resistance genes in the turtles’ microbiome linked to antimicrobials commonly used in human and veterinary medicine. Despite its reputation as a polluted feeding ground, Guanabara Bay remains a key developmental habitat for juvenile green turtles. Our findings reveal their compromised health status and underscore the critical impacts of human activities and pathogens on these turtles and their environment.