4.3.1 Dredging
Dredging of the sea floor will cause increased suspended sediment and turbidity. This will directly affect seagrass and macro-invertebrate communities, beyond direct effects of habitat destruction and through the dredging process. Dredging activities can have major impact on coastal ecosystems, decreasing the amount of light available for photosynthesis, covering seagrass beds, coral reefs of fish spawning sites with a layer of sediment, or leading to suspension of pollutants which accumulate on the seafloor (Kuster et al. 2007 in Petus and Delvin 2012). The removal of large quantities of sediment can damage nearby coral reefs.
Impacts depend on exposure during operations (Salvat 1987). The removal of habitat reduces the productivity of the harbour and its ability to support fish populations (Hunt 2011). The dredge spoil is reportedly toxic, and the suspended sediment from this is also an issue. The toxins are reported to be from the industrial history in the region (Landos 2012).
The spread of mobilised sediment in the GBR is a serious issue associated with dredging.
As most dredging occurs in sheltered bays, the fine sediment remains suspended for long periods can be dispersed by tidal currents, thereby affecting more distant sites - the dredge
22 See appendix B examples of the approval and conditions for the LNG and dredging.
60 sediment plumes in Gladstone have been mapped 32km from the Harbour (Petus and Delvin 2012). This indicates that the impacts of the development are not only on a local scale, but have a region wide impact. While the plumes travelled the length of the coast, there is also the possibility of this spreading outwards to the pristine Heron-Wisteria complex, 50km east of the mainland [Figure 3.4].
4.3.2 Seagrass, mangroves and coral
The Gladstone region is primarily a seagrass bioregion, established in the 2004-zoning plan (GBRMPA 2011d). Seagrasses are a unique group of flowering plants that have adapted to live fully submerged in seawater, and provide numerous ecological roles within the marine environment (Orth et al. 2006). Seagrasses and mangroves are keystone ecosystems that provide unique habitat for high densities of marine species with respect to diversity and abundance (Blaber 1980; Robertson & Duke 1987; Morton 1990). One of their most important ecological roles is their function as a nursery ground for marine species (Nagelkerken et al. 2000). Seagrass beds also provide important connections between reef habitats and bioregions, interrupt freshwater discharge, are sinks for terrestrial pollution, and can generate an environment with clear, nutrient poor waters, which promotes coral reef growth offshore (Moberg and Folke 1999). Seagrasses, particularly in the GBR, act as a buffer between catchment inputs and reef communities (Waycott et al. 2005).
It is obvious that seagrass beds are important ecosystem providers, especially when surrounding coral reef ecosystems. However the rate of degradation of coral reefs and seagrass meadows is globally increasing as a result of direct human pressures (Schaffelke et al. 2005). An established seagrass ecosystem exists within the GBRMPA zone that also encompasses Gladstone Harbour. The seagrass habitat is in a very vulnerable position due to coastal development, port activities, and urban and industrial runoff (Coles et al. 2007). A baseline survey mapped 13,578 ha of seagrass habitat within the Port Curtis and Rodds Bay area (Rasheed et al. 2003 in Hunt 2011), with estimates of 15% likely to be affected by direct anthropogenic (specifically industrial) impacts (Hunt 2011). Seagrass levels are not only affected by physical removal, but the disturbance of sediment by the dredging processes will cause a reduction of light availability, blocking the photosynthetic process required for seagrass, as well as increasing pollutants such as heavy metals and petrochemicals, which seagrass absorb and can be heavily affected by (Schaffelke et al.
2005).
61 Figure 4.3: Seagrass areas mapping in Gladstone Harbour, and the multiple zones (black dotted line for port exclusion zone, red line for GBRMP) (seagrass health 2011)
Seagrass in the GBR region is also important as a major feeding ground for sea turtles [Table 1.1] and dugongs both of which are protected marine species and have strong links to indigenous Australian culture in the region [Figure 1.2]. For these reasons, the seagrass meadows in the Gladstone region are a protected dugong sanctuary (Coles et al. 2007). With increased shipping and industry in the area, dugongs and sea turtles will be heavily affected by the loss of feeding habitat (Hodgson and Marsh 2006). There is also a threat of poisoning and bioaccumulation of heavy metals from contaminated seagrass (Landos 2012). Both dugongs and sea turtles are already on the endangered species list because of direct anthropocentric consequences (Hodgson and Marsh 2007), and the protection of these species is a vital part of the WHL of the GBR and for the maintenance of the OUV of the reef (Marsh et al. 1999; Dryden et al. 2008).
Mangroves are intertidal marine plants, and support the shoreline by reducing erosion, and also benefit the marine ecosystem through nutrient uptake and turnover, carbon sink and sequestration, sediment trapping, and habitat formation and protection (Tomlison 1986).
Mangroves are extremely important ecosystem providers for a suite of organisms, and are especially important in providing a safe habitat for juvenile crustaceans, molluscs and fish
62 during development into adulthood (Nagelkerken et al.2000). This is well represented in the lifecycle of the Red Emperor, which is an iconic fish in coral reef ecosystems (Hutchings et al. 2008).
Figure 4.4: the Red Emperors lifecycle journey (Ryan [artist] in Hutchings et al. 2008)
Between 1941 and 1999, 1,470 ha of mangroves were cleared in the Gladstone region (Duke et al. 2003). Destruction of mangrove forests is mostly due to reclamation for coastal development around estuaries. This has resulted in river bank destabilisation, deterioration of natural water flow, and loss of key coastal marine habitat (Schaffelke et al. 2005). The removal and destruction of mangrove ecosystems also has dire implications on the lifecycle of many reef species, including those important in the fishing sector.
4.3.3 Marine life
The East Banks Dredge dump site has seen an increase in disease in fish since early-2011;
reports of dead fish and diseased fish and crabs are also reported from the Narrows (Petus and Delvin 2012). While there is no conclusive evidence for the cause of the increased disease, the majority of fishermen and researchers in the region attribute this directly to increased dredging activity (Hunt 2011; Landos 2012). The rebuttal of this by GPC attests
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64 important calving ground. Humpback whales will be most impacted by the increase in shipping based on these factors (Smith et al. 2012).
4.4.4 Terrestrial life
Marine species are not the only animals threatened by the development around Gladstone, with concern for the critically endangered Yellow Chat, which is endemic to the Fitzroy Basin area (Houston et al. 2004b). The Yellow Chat has been found on Curtis Island, but in recent years the numbers have diminished rapidly (Houston et al. 2004a, 2004b, 2006).
Industrial development and unrestricted access to the bird‘s natural habitat are identified as some of the major threats to this species (Houston and Melzer 2008).
4.3.5 Transport impacts
Boat traffic causes disturbance through noise and boat strikes, and persistent interruptions will undoubtedly have impacts on the behaviour of dugongs and sea turtles, including their feeding and mating patterns. This will affect the reproductive success of these species, and could lead to their displacement from the area, or even local extinction. Dugongs are already restricted to coastal waters around seagrass meadows, particularly wide shallow protected bays, and are therefore particularly vulnerable to boat strikes (Marsh et al. 1999; Hodgson and Marsh 2007). Turtles are also affected by boat strikes, with a significant level of mortality seen along the east coast of Queensland each year (Hazel and Gyuris 2006). MPAs have been recognised as an effective tool for protection for sea turtles, and the threats of coastal development, habitat loss and boat strikes are well documented threats to their survival (Dryden et al. 2008). Curtis Island is a significant turtle nesting site within the region, and increased development, boat traffic and habitat destruction will impact these local populations (Dryden et al. 2008).
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4.4 Conclusion
The historical context of Gladstone paints an image for its future as the industrial character of the town and harbour has, in part, eased the pathway for the current development to occur. The current developments are also important in contextualising the wider environmental impacts of increased coastal infrastructure development. If local patches of habitat collapse, a system-wide threshold may be surpassed that drives a larger scale regime shift (Hughes et al. 2007). Thresholds are dynamic and difficult to predict, because tipping points change in response to both local and larger-scale processes (Hughes et al. 2007).
While the potential environmental impacts are a cause of concern, the spatial element of locality and concentration, all occurring within an internationally protected zone and adjacent to a National Park raise further concern. While there is little doubt that physical processes of the GBR are changing, in part as a result of anthropocentric influences (Douvere and Badman 2012), coastal and port developments have impacts on the values associated with the OUV. This is particularly so with respect to the cumulative additional pressures on significant marine habitats and protected species which are of high concern to the WHA (Douvere and Badman 2012).
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