Effects of Wide-Spread Natural Disaster Events on the Mortality Rate and Epidemiology of Marine Turtles and Dugongs, Queensland Australia
Abstract
In late December 2010, the northern Queensland coastline was subjected to Category 1 Cyclone Tasha followed in early February 2011 by Category 5 Cyclone Yasi. Along the majority of the coastline, marine habitats and seagrasses were mechanically destroyed. In addition to these events under the same influence of low pressure systems, December 2010 through to February 2011 experienced record 100-year high flooding occurring state-wide. This resulted in the Australian Government declaring the state of Queensland a Natural Disaster Zone. In the days to weeks that followed, fresh water containing high sediment and contaminant loads flowed into the coastal bays causing further loss of habitat and seagrasses, predominantly by lowering salinity and smothering the remaining herbage. Significant loss of seagrass beds was recorded at hotspots along the eastern Queensland coastline.1
Five to 8 months after these natural disasters, a marked increase in the number of recorded marine turtle and dugong deaths occurred. For 2011, there were 1505 reported marine turtle and 187 reported dugong deaths along the Queensland coastline. This contrasts previous year (2008–2010) averages of 843 and 64, respectively.2,3 Further, there was a noted shift in the cause of mortality. For a subset of the animals which presented between 2005 and 2010 to experienced biologists at the Queensland Government's Department of Environment and Resource Management and/or veterinarians at the Veterinary-Marine Animal Research, Teaching and Investigation (Vet-MARTI) unit at The University of Queensland, marine turtle deaths were assigned 24.2% [n = 879, 95% CI 22.8–25.6] due to human-related causes, 5.1% [185, 4.4–5.9] to natural causes, and 70.7% [2571, 69.2–72.2] were unknown. In 2011, 15.8% [3, 3.9–39.6] were due to human-related causes, 78.9% [15, 54.4–93.4] to natural causes, and 5.3% [1, 0.1–26.0] were unknown.4,5 Between 1997–2010, dugongs presenting to the same facilities had deaths assigned as 25.6% [11, 13.5–41.2] due to human-related causes, 44.2% [19, 29.1–60.1] to natural causes, and 30.2% [13, 17.2–46.1] were unknown. In 2011, 12.5% [2, 1.6–38.3] were due to human-related causes, 31.3% [5, 11.0–58.7] to natural causes, and 56.3% [9, 29.9–80.2] were unknown.6
In marine turtles, these shifts may reflect starvation due to loss of habitat and seagrasses, and the development of secondary pathologies and parasitism; presumably due to weakened states to defend against infection. In dugongs, these shifts may represent misadventure due to migration into novel habitats to seek food and the consumption of novel potentially toxic foods, and the transmission of new diseases into previously naïve populations.
Since the natural disaster, the Australian Government has implemented necropsy training programs to veterinarians and research biologists to better determine the causes of death in these species. The rationale of this training was to increase the collection of information to refine management plans and implement mitigation strategies to lessen the devastating effect when future natural disasters occur.
Acknowledgements
The authors wish to thank Dr. Col Limpus and staff of the Queensland Department of Environment and Resource Management for support coordinating carcasses, and Prof Ruth Francis-Floyd of the University of Florida's College of Veterinary Medicine for financial support to attend this conference.
References
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