Moreton Bay Case Study
To date, there is very little information on the type and levels of contaminants in the marine environment of Australia. Over the past years, a number of studies have been initiated that investigate the presence and distribution of POPs (in particular dioxins and dioxin-like contaminants) in the environment from Australia, including Moreton Bay. The studies in Moreton Bay aim to evaluate the distribution these contaminants in sediments, their accumulation in seafood and other biota and to investigate their sources. One of these studies also aims to assess the exposure of the North Stradbroke Island community via consumption of locally sourced seafood and intends to provide the community with the opportunity to engage in and learn about these issues and the associated studies. The latter will be provided by the researchers via locally distributed newsletters and community workshops. The following provides an overview on the results of some of these studies.
Dioxins in Moreton Bay Sediment (Hermanussen et al 2006)
A study was carried out to determine the distribution of dioxins in Moreton Bay surface sediments. To obtain a clearer picture of this distribution, approximately 300 ??check?? sediment samples were collected and analysed. The results were then interpreted using spatial analysis software to predict the dioxin concentrations between the sampled points, as shown in the map below: p
The dioxin concentrations in sediments from Moreton Bay range from very low, background concentrations (0-100 pg/g dry weight) to levels that can be considered elevated (i.e. are comparable to those in sediments from more industrialized areas). . The highest concentrations are found in the southern and western parts of the bay (however, the northern parts have not been included in this study). The lowest concentrations are present around the eastern sandbanks near Moreton and Stradbroke Island. Despite the higher levels at some sites, the toxic equivalency (or TEQ; an estimate of the toxic potency of the dioxin mixture present) is relatively low in most Moreton Bay sediments, meaning exposure of humans via direct contact with sediment is not of concern. As expected, this TEQ increases from bottom feeding fish to higher trophic animals, such as tuna, mackerel, and also loggerhead turtles. The TEQ is also higher in the more sessile marine organisms caught from western, compared to eastern habitat locations. In organisms that move and feed throughout the bay, TEQlevels are similar among different locations within Moeton Bay.
Dioxins and Dioxin-like Compounds in Moreton Bay Seafood (Matthews et al 2008)
As previous studies identified elevated levels of dioxins in sediments and megafauna (dugongs and turtles) in the marine environment of southeast Queensland, this study aims to establish baseline information on dioxin and other dioxin-like compound contamination in a range of seafood species from Moreton Bay and to investigate environmental and other factors that influence contaminant concentrations in seafood. The following graph provides an overview on the TEQ levels found in a number of seafood species from Moreton Bay:
Overall, the TEQ levels in seafood from Moreton Bay were found to be higher compared to background levels reported for Australian marine/estuarine (National Dioxins Program 2004) and retail fish (FSANZ 2004).
However, TEQ levels of most seafood from Moreton Bay were well below those present at highly polluted areas such as Sydney Harbour (NSW Food Authority 2006) and mostly below international limits for human consumption (European Commission, 2006).
FSANZ 2004. Dioxins in Food: Dietary Exposure Assessment and Risk Characterisation. Canberra, Food Standards Australia New Zealand.
Hermanussen, S., Limpus, C., Paepke, O., Connell, D.W., Gaus, C., 2006. Foraging habitat contamination influences on green sea turtle PCDD/F exposure. Organohalogen Compounds 68, 592–595.
Matthews, V., Paepke, O., Gaus, C., 2008. PCDD/Fs and PCBs in seafood species from Moreton Bay, Queensland, Australia. Marine Pollution Bulletin, doi:10.1016/j.marpolbul.2008.01.034
Mueller, J., Muller, R., Goudkamp, K., Mortimer, M., 2004. National dioxins program: dioxins in aquatic environments in Australia. Department of the Environment and Heritage.
NSW Food Authority, 2006. Dioxins in Seafood in Port Jackson and its Tributaries.