Contaminant pathways in Port Curtis: Final report - OzCoasts

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Contaminant pathways in Port Curtis: Final reportExecutive summarySublethal indicators of contaminant exposureImposex was detected in mulberry whelk specimens collected from Port Curtis,confirming a sublethal, biological response to TBT exposure. Although related tolocal shipping intensity, the frequency and grade of the imposex condition werenot severe in comparison to surveys of other ports in Australia and overseas.Globally, the condition is likely to slowly improve with the introduction of furtherrestrictions on the use of TBT in 2008.The concentrations of stress biomarkers (glutathione, glutathione-s-transferase,catalase and lipid peroxidase) in field-deployed oysters were quite variable, andfew consistent trends were observed that could be related to contaminantexposure. No firm conclusions could be drawn regarding the suitability of thesebiomarkers for biomonitoring in Port Curtis.Contaminant foodweb dynamicsA food web including mud crabs, other crustaceans, fish, molluscs and a variety ofplants was characterised in Port Curtis. In general, the food web was not unlikethose established for other estuarine embayments. It appears that very fewspecies rely on mangroves as a predominant food source but are more dependenton benthic organic matter and algae. Mud crabs were identified as one of thedominant predators in the food chain. Carbon isotope measurements suggestedthat prawns were feeding either directly or indirectly on a blue green algal bloom(Lyngbya majuscula) and this finding was supported by observations of pigmentfrom the algae being visually evident in the prawns.The finding may have consequences for consumers should the toxin produced bythe algae follow similar uptake pathways to the pigment and accumulate in theprawn muscle tissue. Although there were very few significant between-sitedifferences in metal bioaccumulation, organisms from inner harbour sites tendedto be more enriched in metals than those from the reference site outside theharbour. The findings of this study indicate that for the majority of organisms theuptake of metals through food pathways is likely to be complex and integrated,particularly for those in higher trophic positions and those that have the ability toregulate metal accumulation.Pulse exposure to contaminantsContaminant pulse studies were conducted in the laboratory using the marine algaPhaeodactylum tricornutum as the model organism and copper as the modelviii
Contaminant pathways in Port Curtis: Final reportExecutive summarycontaminant. These studies suggest that, at least for microalgae over shortexposure times (up to 72 h), bioaccumulation of copper from pulse exposure is nogreater than bioaccumulation from continuous exposure. Copper bioaccumulationmeasurements indicated that P. tricornutum did not have an effective mechanismfor eliminating copper from cells, rather the intracellular copper decreased as aresult of dilution by cell division. If predictive models were developed for keyorganisms in Port Curtis, this would allow better assessment of pulse exposure.This approach is currently the best practicable approach to solving this complexproblem.Future directionsAfter six years of activity, the Coastal CRC has left a lasting legacy in Port Curtis.There is an increased awareness amongst stakeholders of contaminant issuesbased on good quality data. The CRC study was the first to adopt a whole-of-portapproach to understanding contaminants in Port Curtis. With a few exceptions, themajority of previous research had either not focussed on contaminants or theireffects, or had been limited to studies of particular receiving environments.Specific project outputs, including reports, press releases and research papers,are listed in the appendix. A considerable database of accurate contaminantdistributions is now available for utilisation by local industry, researchers andregulators alike. The ‘report card’ for contaminants in Port Curtis is generally quitegood, although a recent oil spill event illustrates the sensitivity of the ecosystemand the need for reliable baseline information and strong environmentalmanagement.In the future, is it envisaged that the Port Curtis Integrated Monitoring Program(PCIMP) and the Centre for Environmental Management (CEM) at the Gladstonecampus of Central Queensland University (CQU) will carry on the legacy of theCRC. PCIMP is a consortium of members from 14 bodies representing industry,government (both local and state), research institutions and other stakeholders todevelop a cooperative, integrated program for monitoring the ecosystem health ofPort Curtis. A strong, long-term, annual monitoring program, building on the initialgroundwork established by the CRC, is being formulated by PCIMP members inconsultation with local stakeholders. Research will focus on water and sedimentquality—particularly bioavailable contaminants—and on mangrove ecosystems.Results will be presented to the community in the form of an Ecosystem HealthReport Card for Port Curtis.Based on the CRC studies of the last six years, we suggest the followingdirections for future contaminants management and research:ix
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