Office for Environmental Programs - Theses
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ItemEffects of experimental flooding on egg survival of Krefft's River Turtle: implications for freshwater turtle conservation( 2012)Anthropogenic changes to river catchments via changes to flow rate and volume can dramatically influence biodiversity. Most of Australia's major rivers are now impounded from the construction of dams and weirs causing the loss and significant alteration to habitat due to modified flow regimes. Such changes can negatively impact biodiversity, particularly specialist species. For example, anthropogenically altered flow regimes expose freshwater turtle to a seasonal inundation events that are assumed to exacerbate egg mortality during the incubation phase. Thus flooding of freshwater turtle eggs has been identified as an additional threatening process that could further impact both listed and non-listed freshwater turtles. Consequently, understanding the degree of mortality imposed on turtle eggs during incubation is a crucial step to ascertaining management implications from altered flow regimes on turtle populations. Here I conducted experiments to specifically identify the effects of 1) duration and 2) timing of inundation on Emydura macquarii krefftii egg hatching success and hatchling phenotypes. This was done in order to measure both direct and potentially indirect mortality costs associated with altered river flow regimes. Four treatments of eggs; control, 30 minutes submersion, one hour submersion and 6 hours submersion were flooded at nine periods during incubation (within the first 24 hours then every week following). Analysis revealed that inundation for any length of time caused a significant increase in egg mortality compared to control eggs. The developmental age at which inundation treatments were applied also had a significant impact on hatching success, with age 0 exhibiting the highest mortality rate and other developmental ages displaying fairly similar but increased mortality relative to controls. These results suggest that E. m. krefftii eggs are very sensitive to even brief episodes of inundation, especially within the first 24 hours of incubation. Moreover, if other turtle species are proven to exhibit similar sensitivities to inundation during egg incubation from altered river flow regimes these results suggests additional and potentially high mortality to all terrestrial nesting freshwater turtles. Ultimately these results support the need to prioritise informed management of anthropogenically altered flow regimes in order to prevent potential loss of an entire guild of vertebrates and their ensuing ecological function