The distribution of metal and petroleum-derived contaminants within sediments around oil and gas infrastructure in the Gippsland Basin, Australia.

As oil and gas infrastructure comes to the end of its working life, a decommissioning decision must be made: should the infrastructure be abandoned in situ, repurposed, partially removed, or fully removed? Environmental contaminants around oil and gas infrastructure could influence these decisions because contaminants in sediments could degrade the value of the infrastructure as habitat, enter the seafood supply if the area is re-opened for commercial and/or recreational fishing, or be made biologically available as sediment is resuspended when the structures are moved. An initial risk hypothesis, however, may postulate that these concerns are only relevant if contaminant concentrations are above screening values that predict the possibility of environmental harm or contaminant bioaccumulation. To determine whether a substantive contaminants-based risk assessment is needed for infrastructure in the Gippsland Basin (South-eastern Australia), we measured the concentration of metals and polycyclic aromatic hydrocarbons (PAHs) in benthic sediments collected around eight platforms earmarked for decommissioning. The measurements were compared to preset screening values and to background contaminant concentrations in reference sites. Lead (Pb), zinc (Zn), PAHs and other contaminants were occasionally measured at concentrations that exceeded reference values, most often within 150 m of the platforms. The exceedance of a few screening values by contaminants at some platforms indicates that these platforms require further analysis to determine the contaminant risks associated with any decommissioning option.

Gamma-irradiation of common biological samples for stable carbon and nitrogen isotope and elemental analyses.

RATIONALE: Around the world biosecurity measures are being strengthened to prevent the spread of pests and diseases across national and international borders. Quarantine protocols that involve sample sterilisation have potential effects on sample integrity. The consequences of sterilisation methods such as gamma (γ)-irradiation on the elemental and chemical properties of biological samples have not been widely examined. METHODS: We tested the effect of γ-irradiation (50 kGy) on the stable carbon and nitrogen isotope compositions (δ13 C and δ15 N values) and elemental concentrations (C % and N %) of common biological samples (fish, plants and bulk soils). The analysis used a continuous flow system consisting of a Delta V Plus isotope ratio mass spectrometer connected with a Thermo Flash 1112 elemental analyser via a ConFlo IV interface. Results were compared using two one-sided tests (TOST) to test for statistical similarity between paired samples. RESULTS: There was no change in the δ15 N values or N % of γ-irradiated samples, and only small changes to the δ13 C values of consumers (range: 0.01‰ to 0.04‰), producers (-0.02‰ to 0.04‰) and sediments (0‰ to 0.07‰). The magnitude of change in δ13 C values was greatest at low carbon concentrations but appeared negligible when measured against replicated sample analysis and the combined analytical uncertainty (i.e., 0.10‰). The C % values of irradiated samples were higher for consumers (0.23%) and lower for producers and sediments (0.04% and 0.05%, respectively) which may have implications for certain types of biological material. CONCLUSIONS: Routine γ-irradiation has little effect on the stable carbon and nitrogen isotope compositions of common biological samples and marginal effects on carbon elemental concentrations. This is unlikely to warrant concerns since the observed difference is typically of a magnitude lower than other sources of potential uncertainty.

Multi year observations reveal variability in residence of a tropical Demersal Fish, Lethrinus nebulosus: implications for spatial management.

Off the Ningaloo coast of North West Western Australia, Spangled Emperor Lethrinus nebulosus are among the most highly targeted recreational fish species. The Ningaloo Reef Marine Park comprises an area of 4,566 km2 of which 34% is protected from fishing by 18 no-take sanctuary zones ranging in size from 0.08-44.8 km2. To better understand Spangled Emperor movements and the adequacy of sanctuary zones within the Ningaloo Reef Marine Park for this species, 84 Spangled Emperor of a broad spectrum of maturity and sex were tagged using internal acoustic tags in a range of lagoon and reef slope habitats both inside and adjacent to the Mangrove Bay Sanctuary zone. Kernel Utilisation Distribution (KUD) was calculated for 39 resident individuals that were detected for more than 30 days. There was no relationship with fish size and movement or site fidelity. Average home range (95% KUD) for residents was 8.5±0.5 km2 compared to average sanctuary zone size of 30 km2. Calculated home range was stable over time resulting in resident animals tagged inside the sanctuary zone spending ∼80% of time within the sanctuary boundaries. The number of fish remaining within the array of receivers declined steadily over time and after one year more than 60% of tagged fish had moved outside the sanctuary zone and also beyond the 28 km2 array of receivers. Long term monitoring identified the importance of shifting home range and was essential for understanding overall residency within protected areas and also for identifying spawning related movements. This study indicates that despite exhibiting stable and small home ranges over periods of one to two years, more than half the population of spangled emperor move at scales greater than average sanctuary size within the Ningaloo Reef Marine Park.

Detection of Minchinia sp., in rock oysters Saccostrea cuccullata (Born, 1778) using DNA probes.

Haplosporidian parasites infect various invertebrate hosts including some commercially important shellfish. Haplosporidium nelsoni (along with Perkinsus marinus) has severely affected Eastern oyster production on the eastern seaboard of the United States and flat oyster production in Europe has been severely impacted by Bonamia ostreae. These parasites are also often present at a very low prevalence and there are a variety of morphologically similar species that can be difficult to differentiate during cytological or histological diagnosis hence the need to develop specific tests. Recently, a Minchinia sp. was described affecting rock oysters (Saccostrea cuccullata) in north Western Australia. In this study, two in situ hybridisation (ISH) assays and a PCR assay have been developed and optimised for use in investigating these parasites. The first ISH assay used a 166bp polynucleotide probe while the second used a 30bp oligonucleotide probe. The specificity of each ISH assay was assessed by applying each probe to a variety of haplosporidian (5), a paramyxian (1) or ciliophora (1) parasites. The polynucleotide probe produced strong hybridisation signals against all of the haplosporidian parasites tested (Minchinia sp., Minchinia teredinis, Bonamia roughleyi, H. nelsoni and Haplosporidium costale) while the oligonucleotide probe recognised only the Minchinia sp. Both probes failed to detect the paramyxian (Marteilia sp.) or the Rhynchodid-like ciliate. The PCR assay amplifies a 220bp region and detected Minchinia sp. DNA from 50ng of genomic DNA extracted from the tissues of infected oysters and 10fg of amplified Minchinia sp. DNA. The assay did not react to oysters infected with H. nelsoni or H. costale. The ability of the PCR and oligonucleotide ISH assay to diagnose Minchinia sp. infected oysters was compared to histological examination from a sample of 56 oysters. The PCR assay revealed 26 infections while histological examination detected 14 infections. The oligonucleotide ISH assay detected 29 infections. The oligonucleotide ISH and PCR assays were found to be significantly more sensitive than histology for detecting the parasite.

Molecular characterisation of a haplosporidian parasite infecting rock oysters Saccostrea cuccullata in north Western Australia.

A haplosporidian parasite was identified in rock oysters (Saccostrea cuccullata Born, 1778) from the Montebello Islands (latitude -20.4'S longitude 115.53'E) off the northern coast of Western Australia by histopathological examination, PCR amplification and DNA sequencing of a segment of the SSU region of the parasite's rRNA gene. An oligonucleotide probe was constructed from the parasite's SSU rRNA gene in order to confirm its presence by in situ hybridisation. The parasite was disseminated throughout the gonad follicles of the host and to a lesser extent in the gills. The only parasite life stages thus far observed in this study were a uninucleate naked cell assumed to be a precursor to multinucleate plasmodial stages and a binucleate plasmodial stage. Whilst no parasite spores were detected in affected rock oysters, a phylogenetic analysis of the SSU region of the parasite's rRNA gene indicates the parasite belongs to the genus Minchinia. A PCR and in situ hybridisation assay for the Minchinia sp. was used to identify haplosporidians described by Hine and Thorne [Hine, P.M.., Thorne, T., 2002. Haplosporidium sp. (Haplosporidia: Haplosporidiidae) associated with mortalities among rock oysters Saccostrea cuccullata in north Western Australia. Dis. Aquat. Organ. 51, 123-13], in archived rock oyster tissues from the same coastline.