GREAT BARRIER REEF
// Outlook Report 2014
corals86 and widespread damage to seagrass meadows95. Investigations show that the poor health observed in a range of fish species in Gladstone harbour during 2011 was likely to be the result of multiple pressures, but in particular overcrowding of fish after an overspilling of Awoonga Dam during a high flow event.155 Examination of a 17-year dataset for the urban coast of Queensland found peak mortality of dugongs followed sustained periods of freshwater discharge and low air temperature.96 While the contribution of key pollutants from terrestrial point source discharge is relatively small when compared to diffuse pollutant sources, the impacts can be locally significant.73 There is no specific evidence linking pollutants such as heavy metals to declines in marine species in the Region, however they can persist for decades in the marine environment and have been shown elsewhere to disrupt reproduction, impair immune systems, affect neurological systems and cause cancers294. Marine debris, including that introduced into the marine environment through land-based run-off, poses a significant threat to wildlife, including species of conservation concern. They can choke on it, ingest it, become entangled in it, or absorb Marine debris poses a significant threat to wildlife © Chris Jones chemicals from it.295 In Australia, plastic waste, including discarded fishing gear (for example nets, lines and ropes), is potentially one of the most harmful types of debris to marine wildlife because of ingestion and entanglement.296,297,298,299 Marine debris of all sorts can affect species and habitats throughout the Region. Land-based run-off also plays a role in transporting terrestrial weed species onto islands within the Region.
Marine debris washed from the land continues to affect the Region’s ecosystem.
6.5.3 Vulnerability of heritage values to land-based run-off
Many of the Region’s heritage values, such as world and national heritage values, natural heritage values and Indigenous heritage values are vulnerable to the threats associated with land-based run-off through their effects on the ecosystem (Section 6.5.2). The threats associated with land-based run-off have affected many attributes that contribute to the outstanding universal value of the Reef, for example its coral reef and seagrass habitats and its underwater beauty. Particularly in inshore areas of the southern two-thirds of the Region, underwater aesthetic values are being affected by overall declines in ecosystem condition. These values are also being diminished by increases in turbidity as a result of sediments and nutrients in land-based run-off, combined with marine debris. It is likely that increased sedimentation is also affecting underwater historic heritage such as shipwrecks and World War II artefacts. Cultural practices have been affected by concerns about heavy metal contamination of species of cultural significance, resulting from terrestrial point source discharges. High levels of heavy metals have been detected in the livers of turtles in the Torres Strait300 and dugongs253, which could pose health risks to Indigenous people. In the Gladstone region, some Traditional Owners consider the health of turtles to be so poor they have stopped taking them as part of their cultural practices.301
Many heritage values are vulnerable to the effects of landbased run-off.
6.5.4 Implications of land-based run-off for regional communities