Conservation of the endangered loggerhead turtle (Caretta caretta): Correlations between environmental contaminants, genetic origin, health and hatching success of Western Australian populations.

A project undertaken at the School of Veterinary and Biomedical Sciences, Murdoch University, and supervised by Dr Kristin Warren.

Worldwide, numbers of loggerhead sea turtles have declined dramatically, and they are now Endangered in Australia and internationally. Western Australia has major foraging and nesting grounds for loggerheads, including large rookeries in Ningaloo and Shark Bay. Despite WA loggerheads being distinct genetic stock from Eastern Australian populations, there are no long-term data available for WA loggerheads. Data on health and hatching success are fundamental for developing turtle conservation strategies, and Australian turtle Recovery Plans prioritize research into factors affecting both parameters. This multidisciplinary project will undertake the first study, for WA loggerhead turtles, of genetic origins; environmental toxins; and correlations between these and human impacts, health, and hatching success. Results will improve our knowledge of WA sea turtle population health, and will be important for turtle recovery efforts and WA biodiversity conservation.

The experimental design incorporates two of WA’s three major loggerhead sea turtle nesting sites: Dirk Hartog Island in the Shark Bay World Heritage Area; and Bungelup Beach in Ningaloo Marine Park near Exmouth. The Dirk Hartog nesting population alone may represent 70% of nesting loggerheads across the eastern Indian Ocean. Field data and biological samples will be collected annually for two nesting seasons from November-March, to enable toxicological, histological, genetic and correlation analyses. These two key loggerhead nesting locations are also marine parks of national and international conservation significance.

This study, with its focus on toxicology and genetic origins, forms a distinct and key component of a broader study which is the first assessment of the health status of WA loggerhead turtle populations. Our specific aims are:

1. To measure toxin levels (POPs, heavy metals) in unhatched eggs, to quantify environmental toxins as risk factors that may reduce hatching success on WA beaches ('pristine' Shark Bay vs Exmouth). The broader health/hatching success study is examining other factors in embryo/hatchling death/illness.
   
   
2. To determine types/levels of deformities found in unhatched eggs and dead hatchlings, including histopathology; and to correlate deformities with toxin levels. The broader study involves correlations between hatchling deformities and maternal clinical health/disease.
   
   
3. To correlate toxicology data with disease prevalence (as determined via the broader study) in adults/ hatchlings/post-hatchlings. The broader study will investigate other health risk-factors, particularly in adults.
   
   
4. To determine blood toxin levels in adult nesting females whose nests are sampled. The broader study will assess whether these contaminant levels are associated with abnormal health parameters.
   
   
5. To correlate findings of the toxicological screenings and histopathology with hatching success and nesting female reproductive success.
   
   
6. To determine genetic origins of turtles from which toxicological/health screening samples are collected, and to correlate genetic origin with toxin levels and the broader findings on health/disease/ hatching success.

This study will increase our understanding of the factors involved in adult health/disease and hatching success, and will provide data to assess the significance and threat of human-related disturbances. These three outcomes are identified as priorities in Australian sea turtle Recovery Plans and, due to the geographic importance of WA's foraging and nesting grounds, are critical for sea turtle recovery efforts across the Australasian region.