The Gladstone (Australia) oil spill – Impacts on intertidal areas: Baseline and six months post-spill Felicity Melville a, * , Leonie E. Andersen a , Dianne F. Jolley b a Centre for Environmental Management, CQ University, GPO Box 1319, Gladstone, Queensland 4680, Australia b Geoquest, School of Chemistry, University of Wollongong, New South Wales 2522, Australia article info Keywords: Heavy fuel oil Polycyclic aromatic hydrocarbons Sediment Mangroves Crabholes Macroinvertebrates abstract In January 2006, 25 tonnes of heavy fuel oil spilled into the Port of Gladstone in Queensland, Australia, from the breached hull of a bulk carrier ship. While approximately 18 tonnes of the oil was recovered, a certain amount of oil was deposited in the intertidal areas of Port Curtis leaving a highly visible, viscous residue. The objectives of this research were to assess the short-term (one month post-spill) and med- ium-term (six months post-spill) impacts on the intertidal habitat. Sediment polycyclic aromatic hydrocarbons (PAHs) and metal concentrations, mangrove communities and intertidal macroinvertebrates were assessed at oil impacted sites, adjacent sites which were not vis- ibly impacted and reference sites which were located outside the recorded distribution of the oil spill. At one month post-spill, highest PAH concentrations were found at the impacted sites, with concentra- tions of some PAHs exceeding Australian and New Zealand sediment quality guidelines (SQG) [ANZECC/ ARMCANZ, 2000. Sediment Quality Guidelines. Australia and New Zealand Environment and Conserva- tion Council and Agriculture and Resource Management Council of Australia and New Zealand]. However, by six months post-spill PAH concentrations had significantly decreased. PAH concentrations tended to be higher in the back (upper) intertidal zone than at the front of the mangrove stand, and sediment cores indicated that PAH contaminants had remained in the top 4 cm of the sediment. These results indicate that the overall decreased PAH concentrations are likely to be due to evaporation, photoxidation and tidal flushing of the residual oil in these impacted sites. During the initial survey, the impact site contained very few or no crabholes in the high intertidal area, indicating a low crab density in comparison to reference sites. However, at six months post-spill man- grove crab communities appeared to be fully recovered with crabhole densities in impact sites similar to reference sites. While little immediate impact was evident on mangrove parameters, significantly higher seedling mor- tality and defoliation was apparent at six months post-spill, particularly in the upper intertidal zone. Intertidal macrobenthic communities did not appear to be impacted, either immediately or at six months post-spill. Monitoring of these oil impacted intertidal areas will continue to examine the long-term impacts/recovery from the oil spill. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction On January 24th, 2006 at approximately mid-night, oil spilled from a ruptured fuel tank aboard the Korean bulk carrier global peace after a collision with a tugboat (AMSA, 2006). Approximately 25 tonnes of heavy fuel oil was spilt into Gladstone harbour (Aus- tralia) and surface oil dispersed across the harbour. Oil skimmer boats were able to remove patches of heavy oil from the water sur- faces in the worst affected areas and dispersants were not used in the clean-up process. Over 18 tonnes of the oil was recovered, however, due to the prevailing weather conditions at the time of the spill, some oil was deposited in the intertidal areas of Port Cur- tis, leaving a viscous and persistent residue (Andersen et al., 2008). This study aimed to assess the short (within one month post-spill) and longer-term (six months post-spill) impacts of this oil on the intertidal areas by examining sediments, mangroves and macro- invertebrates communities. Oil is comprised of a variety of hydrocarbon-based substances, particularly alkanes, cycloalkanes and aromatics (polycyclic aro- matic hydrocarbons, PAHs), with each type of oil exhibiting distinct physical and chemical properties (CONCAWE, 1998). Heavy fuel oil, as spilled into Gladstone Harbour, is highly viscous and may contain high concentrations of metals. In addition to smothering organisms, 0025-326X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2008.09.022 * Corresponding author. Tel.: +61 7 4970 7309; fax: +61 7 4970 7207. E-mail address: f.melville@cqu.edu.au (F. Melville). Marine Pollution Bulletin 58 (2009) 263–271 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul