Document ID: chunk:federal_register_of_legislation:F2017L00641:body:0:p40
Version: federal_register_of_legislation:F2017L00641
Segment Type: other
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Character Range: 121120–123990

quality. Marine turtles are commonly affected by spirochiid parasites (blood flukes), and other parasites[66]. Bacterial infections can result from injuries caused by boat strikes and/or entanglement in fishing gear[65]. Disease outbreaks in food sources, such as seagrass, can also indirectly affect the health of marine turtles[51].
Fibropapillomatosis is a common disease in marine turtles that presents as internal and external tumours. The cause of the disease is not fully understood, but the disease has been linked to a herpesvirus[118], and appears to be exacerbated by poor water quality[2, 3]. Progression of tumour development has also been linked to exposure to naturally produced tumour-promoting compounds[4, 129]. Severe tumours around the eyes and mouth can limit vision and ability to forage, and tumours on flippers can inhibit swimming ability.
To date, there are no recorded occurrences of diseases and pathogens affecting the viability of a marine turtle stock in Australia. As marine turtle health is likely closely tied to water quality, management of acute and chronic chemical and terrestrial discharge is the primary mechanism for ensuring sub-lethal impacts of disease does not reach epidemic levels. The impacts of poor water quality, sediment loads and toxic chemicals on marine turtle health are considered in Section 4C Chemical and terrestrial discharge. Further research is required to understand stock level impacts of disease and pathogens.

4.2 Cumulative impact of threats
In this plan, the assessment of the risk of any given threat to a stock has been considered in isolation (Section 4.4). However, marine turtles are long lived and have highly dispersed life history requirements. As a result, they are subject to multiple threats acting simultaneously across their entire life cycle causing a cumulative impact on a stock. Similarly, multiple threats may occur at the same time and location and thus provide an interactive impact.
For some stocks there are multiple 'high' and 'very high' risk threats causing a decline. For example, olive ridley turtles nesting on western Cape York have been subject to up to 90 per cent egg loss due to predation by introduced animals and goannas for over a decade[136]. This loss, combined with potentially large numbers of turtles drowning in ghost nets at sea[115] is likely to be resulting in a substantial decline in this stock.
Other stocks may only have a few direct threats rated as 'high' or 'very high' risk, but many 'medium' risk threats that combined could result in the stalled recovery of the stock. For example, flatback turtles nesting in the south-west Kimberley were only determined to be at high risk from acute chemical and terrestrial discharge, but are considered to be at moderate risk from 13 other threats including light glow from urban and industrial development,