GREAT BARRIER REEF
// Outlook Report 2014
chemical and oil spills; some contribution to marine debris; altered light regimes; and diminished aesthetic values. Noise pollution associated with general port activities such as pile driving may be affecting marine life102. However little is known of its effects in the Region. High concentrations of coal dust have been detected around a loading facility103, but the potential effects of this and any other port-generated atmospheric pollution are not well understood. The Outlook Report 2009 stated the impacts of dredging and construction of port facilities — such as seabed disturbance, transport or resuspension of contaminants, alteration of sediment movement and changes in coastal processes — can be significant, but are localised. Since 2009, understanding of the effects of dredging and the disposal and resuspension of dredge material has advanced, although broader regional and cumulative effects on inshore biodiversity remain poorly understood. Many of the inshore environments in which ports operate are already under pressure from an accumulation of other impacts such as those associated with land-based run-off, shipping and coastal development. There is also increased community interest in this activity and its potential effects. The specific effects of dredging activities are well documented and include: seabed disturbance104,105; removal or modification of seafloor habitats106,107; loss of species, including benthic organisms93 and injury or mortality to species of conservation concern104,108; changes in species behaviour109; degradation of water quality106,110 including increased sedimentation and turbidity from dredge plumes105; changes to hydrodynamics and coastal hydrology105; increased underwater noise102; and an increased risk of oil spills109. The most severe effects are at the site of dredging but some, including sedimentation, turbidity, noise and disruption of fish habitats, may also occur some distance from the site. With regard to heritage values, there can be sea burial sites, sacred sites and sites of other cultural significance in the areas where dredging is undertaken and, previously, inadequate consultation with Traditional Owners has meant some of these values have been affected.111 In addition, dredging activities can disturb Indigenous cultural practices112. Aspects of the Region’s aesthetic value such as ‘beauty’, ‘naturalness’ and ‘remoteness’ are considered highly sensitive to industrial development including ports.113 Major direct impacts of sea disposal of dredge material include the burial or smothering of plants and animals on the seafloor106, degradation of water quality93, and loss and modification of habitats105. There is also emerging evidence of a higher prevalence of coral disease in areas exposed to dredge material.114 Understanding of the extent to which dredge material remains within the defined disposal area has improved.115,116 Modelling in a recent screening-level analysis of potential disposal areas — the first to incorporate the effects of large-scale oceanic currents — suggests dredge material has the potential to migrate over greater distances and for longer periods than previously understood (more than 100 kilometres).117 Dredging and disposal of dredge material can also remobilise, redistribute and resuspend sediments and nutrients that were otherwise held within seafloor sediments. Fine sediments can become resuspended over several years by wind and waves, contributing to increased turbidity.118,119 Increases in turbidity reduce the light available for photosynthesis, affecting coral and seagrass habitats and species that rely on them.105 This is particularly significant if these effects happen during periods critical for seagrass survival, growth and reproduction. Increased turbidity also affects coral growth, structure and survival.110,120 The consequential impacts of ports are also linked to those associated with shipping and ship anchorages (Section 5.8).