Contaminant pathways in Port Curtis: Final report - OzCoasts

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Contaminant pathways in Port Curtis: Final reportExecutive summary(i) Risk-based managementThe SLRA illustrated the utility of using a risk-based approach to contaminantmanagement. Owing to limited resources and more time-critical research priorities,the CRC was not able to assess the risks posed by many organic contaminants.We recommend that this issue now be covered, but with a staged approach. TheCRC research has shown the value of using contaminant bioaccumulation as anindicator of ecosystem health. A first stage would therefore be the measurement oforganic contaminants in indicator organisms in Port Curtis. Further investigationsmay be necessary if bioaccumulated organic contaminants prove to be significant.Mercury in piscivorous fish such as barramundi can be elevated owing to foodchain biomagnification. This is an issue of regional importance and should not beforgotten given the large recreational and commercial fishing industries present inPort Curtis and surrounding regions. The characterisation of mercurybioaccumulation and biomagnification through food webs over the coastal regionof the whole Central Queensland region is appropriate.(ii) Improved monitoringThe Contaminant Pathways study and the SLRA have shown the value of ‘goodquality data’. It is recommended that future monitoring adopt and enforce rigorousquality assurance protocols to ensure quality is maintained.As noted earlier, contaminant concentrations may fluctuate over various timescales in Port Curtis. Such variations are not easily discerned with a discretesampling approach. Time-integrated monitoring such as biomonitoring usingdeployed organisms (e.g. oysters) and chemical surrogates such as diffusivegradients in thin films (DGT) for metals and solvent-filled dialysis cells for organics(passive samplers) is therefore recommended. Seasonal monitoring may also beconsidered to determine if there are any seasonal fluctuations to contaminantloads in Port Curtis.(iii) Ability to predict contaminant concentrations and effectsA key tool in sustainable management is the ability to predict impacts. Werecommend that the further development of the hydrodynamic model inconjunction with contaminant data and a subsequent suite of predictive models ispursued. The model should be expanded to include The Narrows region and someof the major estuaries in Port Curtis to assist in understanding the contribution ofmetal load from point sources, and flows from the Fitzroy River to Port Curtis.Predictive models of metal bioaccumulation and biological impact (or establishingif environmental harm has occurred) are also worthy of consideration. The effect ofx
Contaminant pathways in Port Curtis: Final reportExecutive summarypulse versus continuous discharges on bioaccumulation should also be pursued.Information could result in management changes for a more favourable controlledrelease of contaminants at point source discharges.(iv) Future concernsIt is hard to predict the priorities for contaminant management over the nextdecade. It is necessary to keep a watching brief on emerging issues. Unforseenevents such as oil spills and resulting PAH contamination will always be a threat ina busy commercial port, and stringent protocols should be in place to manage andsubsequently assess the impacts of such events. Ross (2002) recently reported asurvey of acid sulfate soils (ASS) in the Central Queensland coast and found highoccurrence of these soils on the coastal plain along the Curtis and Capricorncoasts, Shoalwater Bay and Broadsound. When exposed to air, sulfides areoxidised, producing sulfuric acid and can also release iron, aluminium, and otherheavy metals. This is an issue of potential concern in Port Curtis especially inareas where development results in the aerial exposure of sulfide-containingsediments.The reduced flushing of the estuary highlighted by the hydrodynamic model alsobrings into question the resilience of the estuary in terms of its ability to cope withincreased contaminant loads from new industries or current industry expansions.A number of new industries are proposed in the near future including a nickelrefinery and aluminium smelter, in addition to the expansion of already existingindustries. Bioaccumulation of metals in the inner harbour area has already beendemonstrated indicating that the harbour has potentially a limited threshold forcontaminant loads. Ecosystem health should continue to be monitored over thelong term to ensure the threshold is not exceeded resulting in a decline in thecurrent state of the harbour.xi
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Contaminant pathways in Port Curtis: Final report - OzCoasts

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