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Oil Spill Assessment
In January 2006, oil spilled from a ruptured fuel tank aboard the bulk carrier, Global Peace. While the majority of oil was recovered over the following few days, some oil was deposited in the intertidal zones in the mouth of the Calliope River and near Fisherman’s Landing. As part of the Port Curtis Integrated Monitoring Programs (PCIMP) commitment to the ongoing assessment of health of Port Curtis Harbour, these areas were monitored in order to examine any potential short- and/or long-term effects of the oil spill.
Overall, only a small amount of the mangrove ecosystems within the harbour were affected (less than 0.02%). However, it was important to identify the extent of any unfavourable effects from the oil spill, and examine the recovery of the ecosystem. Not only will this provide valuable knowledge for the stakeholders of Port Curtis, but will also assist in the formulation of a management response for any future oil spills.
An assessment of the mangroves, sediments and invertebrate communities was undertaken shortly after the oil spill, similar to the monitoring strategies used in the Intertidal Monitoring program. This assessment was repeated at 6 months, 12 months and 2 years post-spill. While intertidal crab populations declined considerably immediately following the oil spill, these populations had fully recovered within six months. Concentrations of polycyclic aromatic hydrocarbons (PAHs) in the sediments had also decreased significantly by this time, and continue to do so. While the effects on the mangrove plants did not appear for some time, these included the death of some seedlings and defoliation of mature plants. However, within two years post-spill, recovery of the mangroves in these areas was well underway.
The results of the first two oil spill assessments have been published in an international peer-reviewed journal – Marine Pollution Bulletin. The references for these articles are below:
- Andersen, L. E., Melville, F. & Jolley, D. (2008). An assessment of an oil spill in Gladstone, Australia - impacts on intertidal areas at one month post-spill. Marine Pollution Bulletin 57, 607-615.
- Melville, F., Andersen, L. E. & Jolley, D. (2009). The Gladstone (Australia) oil spill - Impacts on intertidal areas: Baseline and six months post-spill. Marine Pollution Bulletin 58, 263-271.
Results of toxicity testing using sediments collected directly after the oil spill also showed promising results. The oil enriched sediments were diluted to different concentrations and small plants and animals, including algae, tube worms, soldier crabs and barramundi fingerlings, were exposed to varying concentrations to examine what level of contamination caused an adverse effect. The results demonstrated that the oiled sediments had little effect on water column organisms, such as fish, and only short-term effects would be apparent on the sediment-dwelling animals.
While the oil impacted sites have shown tremendous recovery from the spill, these sites will be monitored over the next few years as part of the Intertidal Monitoring Program to examine the full extent of recovery from the spill. This knowledge will be of great importance in the formulation of management strategies for any future oil spills within Gladstone harbour.
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