Sediment traps were deployed in the Gulf of Papua in June–July 1997, to determine fluxes of organic matter and inorganic elements from the photic zone to deeper waters at the base of the continental slope and in the northern Coral Sea. Three stations, ranging from 900 to 1500m depth, had “shallow” traps at 300m below the water surface and “deep” traps set ∼100m above the bottom. Infiltrex II water samplers collected particulate and dissolved organic matter from the Fly, Purari and Kikori rivers, and near-surface water from the shelf of the Gulf of Papua. Samples were analysed for molecular organic biomarkers to estimate the sources of organic carbon and its cycling processes.Dry weight fluxes from the shallow traps ranged from 115 to 181mgm−2day−1 and particulate organic carbon (POC) fluxes ranged from 1.2 to 1.9mM OCm−2d−1 with molar organic carbon to particulate nitrogen ratios (C/N) ranging from 6.0 to 6.5. Fluxes in deep traps were likely influenced by both early diagenesis and entrapment of resuspended shelf sediments. Dry weight fluxes in deep traps ranged from 106 to 574mgm−2day−1 and POC fluxes ranged from 0.6 to 1.5mM OCm−2d−1, with C/N ratios ranging from 8.5 to 10.8. 13C/12C ratios were −20.2‰ to −21.7‰ in all trap samples, indicating that most of the settling POC was “marine-derived”. Shallow traps had δ15N values of 6.3‰ to 7.2‰ while the values in deep traps were 4.9–5.0‰, indicating the N-rich near-surface OC was less degraded than that in the deep traps. The biogenic lipids consisted of hydrocarbon, sterol and fatty acid biomarkers indicative of marine zooplankton, phytoplankton and bacteria. Sterol markers for diatoms and dinoflagellates were abundant in the water samples. Highly branched isoprenoid alkenes, usually attributable to diatoms, were also detected in both water and shallow traps. Traces of C26–C34 n-alcohols indicative of land–plant biomarkers, were found in river water samples and in the shallow sediment traps. A large unresolved complex mixture (UCM) of hydrocarbons, and a uniform distribution of n-alkanes, indicative of petroleum hydrocarbons, were also detected in the traps. Hopane and sterane biomarkers detected in the trap oil were characteristic of a marine carbonate source, and the aromatic hydrocarbon composition distinguished at least two different oil signatures.We concluded that mass and POC fluxes were similar to those reported for other continental shelves and marginal oceans in tropical and subtropical regions. There was a dramatic decrease in POC as particles sank, due to zooplankton repackaging and photochemical and bacterial decomposition. Carbon isotopic and biomarker patterns showed most of the POC in the sediment traps was marine-sourced with only traces of terrestrial input. There was a significant flux of petroleum, which may signal the existence of natural petroleum seeps in this region.

Organochlorines and organophosphates were measured in four fish species (Lateolabrax japonicus, Pagrasomus major, Miichthys miiuy and Epinephalus awoara) and the mussel Perna viridis collected from aquaculture cages in coastal waters of Xiamen, China. Polycyclic aromatic hydrocarbon (PAH) metabolites were also measured in fish bile. Sites in Xiamen coastal waters (the harbour, Maluan and Tongan) are compared with a “cleaner” reference site at Dongshan Island. DDT was found in livers of all fish sampled (May 1998, 1999 and December 1999) ranging from 0.15 to 2.2 μg/g WW, but levels in muscle tissue (<0.5 ng/g to 0.22 μg/g WW) were at least an order of magnitude lower in the harbour, and were not detectable (<0.5 ng/g) in Tongan samples. All other pesticides examined were not detected in fish or mussels, except for dieldrin in one liver sample (0.07 μg/g WW). Food of the caged fish, small fish and dried pellets, had very low (0.015–0.027 μg/g WW) or non-detectable levels of DDT, indicating significant bioaccumulation of contaminants in caged fish and/or other possible sources of uptake (water and sediments). DDT levels in fish varied with species. DDT contamination in fish livers and whole mussels varied significantly with location. Highest concentrations in fish occurred in the harbour, and less consistently so in Tongan. Dongshan and Maluan had comparatively low levels of DDT. Relatively low residues of DDT in both fish and mussels at Dongshan likely reflect lower levels of pesticide input at this reference site. However, the low levels of DDT contamination in fish tissues from Maluan were unexpected in view of the close proximity of the harbour and possibly reflect the removal of particulate-bound contaminants by the intensive bivalve culture there. Consistently high proportions of DDT in the form of the parent compound (p,p′-DDT: fish 30–45%; mussels 40–65%) from all sites suggest recent releases of this chemical to the environment. Levels of two main groups of PAH metabolites (naphthalene and phenanthrene) in fish bile suggest a different environmental distribution pattern than that of pesticides, in that Dongshan fish appear to be no less exposed to hydrocarbons than those from Xiamen coastal waters.

Sediment and filamentous algae were collected from territories of the detritivorous blenny, Salarias patzneri, to identify sources of dietary detritus. Samples were collected during summer and winter and analysed for fatty acid, hydrocarbon and sterol biomarkers. Sediments predominantly contained: even carbon number fatty acids, a high percentage of polyunsaturated fatty acids and a prevalence of n-heptadecane and n-pentadecane. This composition of lipids is typical of organic matter derived from recently deposited algae, or living microalgae. Similarities between sediment and filamentous algal lipids imply filamentous algae may be a major source of detritus in the sediments. Sediments did however have a higher percentage of 16:1ω7 than filamentous algae samples and this is most likely due to inputs to the sediments from diatoms and bacteria. Based on 20:5ω3 concentrations, it was estimated that diatoms accounted for 18% of the organic matter in sediments during summer and 4% in the winter, whilst 18:1ω7 concentrations suggest bacteria accounted for 10% of organic matter in both seasons. In addition, lipid biomarkers indicated that dinoflagellates, corals, cyanobacteria and zooplankton also contribute to sediments, providing a diverse range of dietary nutrients. It is this combination of inputs to sedimentary detritus that provides S. patzneri with essential dietary nutrients.

The composition of essential fatty acids and biomarkers in the tissues of the blenny Salarias patzneri were compared to those in detritus and filamentous algae collected from S. patzneri territories in order to assess the relative contribution of these 2 resources to the diet. The ratio of 16:1 omega7/16:0 and percentage of 18:2 omega6 in S. patzneri body tissue and detritus was found to be significantly different to filamentous algae samples, suggesting that detritus was the major source of dietary lipids assimilated by S. patzneri. High levels of 16:1 omega7 in S. patzneri tissue and detritus relative to filamentous algae suggest that diatoms are an important component of detrital aggregates and S. patzneri diet. These results demonstrate that coral reef fishes assimilate detrital aggregates and confirm that detritus is a valuable dietary resource on coral reefs.

This field study was a combined chemical and biological investigation of the relative rates of weathering and biodegradation of oil spilled in sediments and testing the influence of a bioremediation protocol. The aim of the chemistry work presented here was to determine whether the bioremediation protocol affected the rate of penetration, dissipation or long-term retention of a medium range crude oil (Gippsland) and a Bunker C oil stranded in tropical Rhizophora sp. mangrove and Halosarcia sp. salt marsh environments. Permission for the planned oil spills was granted in the Port Authority area of Gladstone, Queensland (Australia). Sediment cores from three replicate plots of each treatment for mangroves and four replicate plots for the salt marsh (oil only and oil plus bioremediation) were analysed for total hydrocarbons (THC) and for individual alkane markers using gas chromatography with flame ionization detection (GC–FID). Sediments were collected at day 2, then 1, 2, 5 or 6 and 12 or 13 months post-spill for mangroves and day 2, 1, 3 and 9 months post-spill for salt marshes. Over this time, hydrocarbons in all of the oil treated plots decreased exponentially. There was no statistical difference in initial oil concentrations, penetration of oil to depth, or in the rates of oil dissipation between untreated oil and bioremediated oil in the mangrove plots. The salt marsh plots treated with the waxy Gippsland oil showed a faster rate of biodegradation of the oil in the bioremediated plots. In this case only, the degradation rate significantly impacted the mass balance of remaining oil. The Bunker C oil contained only minor amounts of highly degradable n-alkanes and bioremediation did not significantly impact its rate of loss in the salt marsh sediments. At the end of each experiment, there were still n-alkanes visible in the gas chromatograms of residual oils. Thus it was concluded that there was unlikely to be any change in the stable internal biomarkers of the oils over this time period. The predominant removal processes in both habitats were evaporation and dissolution, with a lag-phase of 1–2 months before the start of microbial degradation.

As part of a larger study on the bioremediation of oil spills in tropical mangrove habitats, we conducted a series of flask experiments to test for the presence of hydrocarbon degrading micro‐organisms in representative wetland habitats. Also tested was the biodegradation of selected oils (Gippsland Crude, Arabian Light Crude and Bunker C), that are transported along the Australian coast. We also tested for potential inhibition of biodegradation by natural organics in the mangrove pore waters and evaluated the ability of an oxygen release compound (ORC) to stimulate biodegradative processes. Evaporation was a significant factor in removing the light alkane and aromatic hydrocarbons from air and nitrogen sparged flasks. Evaporation removed ∼27% of the Gippsland, ∼37%of the Arabian, and ∼10% of the Bunker oils. Oxygen was necessary to support biodegradation as expected. The micro‐organisms were capable of biodegrading the non‐volatile saturate fraction of each oil. Degradation removed another 14 of the Gippsland, 30 of the Arabian, and 22 of the Bunker C oils. Normalisation of the individual aromatic hydrocarbon classes to internal triterpane biomarkers indicated some degradation of aromatics in the Arabian Light and Bunker C oils. Although alkane degradation rates were comparable in the three oils, the Gippsland oil had a higher wax content and after 14 days incubation, still contained as much as 25 of the alkanes present in the original oil. Thus, degradation of its aromatic fraction may have been delayed. Based on these results we estimate that Arabian Light Crude oil would have a shorter residence time than the other oils in mangrove sediment. It has a higher content of light hydrocarbons, which are readily removed by both physical and microbial processes. The Bunker C would be expected to have the longest residence time in mangrove sediment, because it contains a larger percentage of higher molecular weight, unresolved components. Comparison of the efficiency of inoculates from three tropical intertidal habitats (Avicennia and Rhizophora mangroves, plus salt marsh sediments) indicated the presence of hydrocarbon degrading micro‐organisms in all three habitats. There was no known history of oil contamination in the soil source area. There was no inhibition of degradation due to addition of mangrove pore waters. The ORC did not facilitate degradation in closed laboratory experiments. These results were used to formulate a bioremediation strategy to treat oiled sediments in mangrove forests in Queensland Australia, which was based on forced aeration and nutrient addition.

This field study was a combined chemical and biological investigation of the relative effects of using dispersants to treat oil spills impacting mangrove habitats. The aim of the chemistry was to determine whether dispersant affected the short- or long-term composition of a medium range crude oil (Gippsland) stranded in a tropical mangrove environment in Queensland, Australia. Sediment cores from three replicate plots of each treatment (oil only and oil plus dispersant) were analyzed for total hydrocarbons and for individual molecular markers (alkanes, aromatics, triterpanes, and steranes). Sediments were collected at 2 days, then 1, 7, 13 and 22 months post-spill. Over this time, oil in the six treated plots decreased exponentially from 36.6 +/- 16.5 to 1.2 +/- 0.8 mg/g dry wt. There was no statistical difference in initial oil concentrations, penetration of oil to depth, or in the rates of oil dissipation between oiled or dispersed oil plots. At 13 months, alkanes were >50% degraded, aromatics were similar to 30% degraded based upon ratios of labile to resistant markers. However, there was no change in the triterpane or sterane biomarker signatures of the retained oil. This is of general forensic interest for pollution events. The predominant removal processes were evaporation (less than or equal to 27%) and dissolution (greater than or equal to 56%), with a lag-phase of 1 month before the start of significant microbial degradation (less than or equal to 7%). The most resistant fraction of the oil that remained after 7 months (the higher molecular weight hydrocarbons) correlated with the initial total organic carbon content of the soil. Removal rate in the Queensland mangroves was significantly faster than that observed in the Caribbean and was related to tidal flushing. (C) 1999 Elsevier Science Ltd. All rights reserved.

This was a study of produced formation water (PFW) discharged into a shallow tropical marine ecosystem on the Northwest Shelf of Australia. A combination of oceanographic techniques, geochemical tracer studies, chemical and biological assessment methods, and dispersion modelling was used to describe the distribution and fate of petroleum hydrocarbons and added nutrients discharged from an offshore production platform. Using fine scale volatile hydrocarbon data, the horizontal and vertical diffusion parameters for a three dimensional dispersion model were calibrated under local conditions. Trace hydrocarbon chemistry studies and integration of the data into a mass balance model, facilitated a comprehensive description of dispersion and degradation pathways and rates. Bio-accumulation into bivalves and water column microbial growth inhibition studies confirmed the chemistry and model predictions that the area of potential biological impact extended to 0.5 nautical miles (∼900 m) from the discharge with additional skewing in the direction of the predominant tidal flows. Impact would be expected to be concentrated in transient surface slicks and near surface seawater. Dispersion and degradation processes were fast enough to prevent any long-term build-up of contamination within the system. Trace levels of oil in the near field sandy sediments were directly related to the magnitude of the daily discharge. The study is a benchmark to help predict the effects of further oil industry expansion in this pristine coastal region.

Several truckloads of mixed waste oil were dumped onto a short section of road and into the intertidal wetlands near Cairns, Queensland in January, 1994. The oil contaminated a band of mangroves 15–44 m wide along approximately 200 m of road. Impacted marsh included Melaleuca forest and high-intertidal mangroves. The initial concentrations of petroleum hydrocarbons in surface sediments reached 17% of the dry weight in heavily impacted areas. These high concentrations observed in limited spatial areas were similar to those observed over large spatial areas after a catastrophic oil spill in Panama in 1986. No large scale biological damage was observed from this localised spill. Clean up efforts and natural dissipation processes reduced sediment hydrocarbon loads to non-acutely toxic levels in 1.5 years in the intertidal mangroves. High hydrocarbon concentrations remained in the Melaleuca sediments for at least two years post spill. Internal molecular markers were used to detail hydrocarbon dissipation and degradation rates. This study provides a contrast between impacts of localised versus catastrophic oil spills in tropical mangrove habitats.

In September 1994 and 1995, scientists from the Australian Institute of Marine Science (AIMS) and the Australian Geological Survey Organisation (AGSO) conducted surveys aboard the Research Vessel Lady Basten to determine the dispersion, fates and effects of Produced Formation Water (PFW) discharged from the Harriet A production platform near the Montebello Islands, on the North West Shelf of Australia. This report describes the non-volatile hydrocarbon chemistry studies.We measured the dispersion of the PFW into dissolved and particulate fractions of seawater using moored high volume water samplers, surface screen samplers and moored and drifting sediment traps. We studied bioaccumulation using transplanted oysters, and we measured dispersion into sediment with benthic grabs. Samples were analysed for total non-volatile hydrocarbons and individual hydrocarbon components using ultraviolet fluorescence spectroscopy (UVF), gas chromatography with flame ionisation detection (GC-FID), and GC with mass selective detection (GC/MS). The hydrocarbon concentrations were used to calculate vertical fluxes and the total concentrations of hydrocarbons in the various ecosystem compartments. A mass balance model was then used to calculate the rates of other important dispersion and degradation processes.We estimate the potential zone of biological impact in the water column extends to a distance of approximately 0.5 nmile (900 m). Concentrations of oil in sediments were too low to indicate potential toxicity. By the collaborative application of oceanographic and geochemical techniques to marine environmental problems, we endeavour to provide effective feedback to the oil industry to gauge the effectiveness of their operational strategies in minimising impact in these pristine regions.