Ron Szymczak

Sources and sinks of unradiogenic osmium runoff from Papua New Guinea

The Fly and Sepik are two of the largest rivers draining the island of New Guinea and among the world’s large rivers in discharge and sediment yield. Sediment from the upper Fly River and its delta have low 187Os/188Os of 0.511–0.560, and sediments from the upper and lower Sepik River have even lower ratios of 0.294–0.418. Filtered waters ( 1.2). Burial of Os of both seawater and riverine derivation occurs in conjunction with organic carbon burial in the Gulf of Papua. There is a negative correlation between the Os isotopic composition of the bulk sediment and the fraction of organic matter of terrestrial origin based on C isotopes. The systematic relationship between C and Os isotopic compositions in these samples indicates that organic matter is the major host of Os in tropical estuarine sediments. The Os/Corg of Gulf of Papua surface sediments is intermediate between that of other modern and ancient sediments. Approximately 1011 mol/yr of Corg and 20–57 mol/yr of Os are buried in the inner shelf (<50 m depth) of the Gulf of Papua over an area of only 21 000 km2, corresponding to 1–3% of the global marine Os burial flux in 0.006% of the total sea surface area. These results suggest that a large proportion of the global burial flux of Os may take place in conjunction with the deposition of low-Corg sediments. Lowering of the Os isotopic composition of ambient seawater due to a large flux of unradiogenic riverine Os may be indicated by the Os isotopic composition of water from the Coral Sea (187Os/188Os=0.844) and marine sediments within the Gulf of Papua. The island of New Guinea is estimated to provide 4–5% of the global riverine Os flux. Given the very large particulate and dissolved flux to the oceans from rivers in the wet tropics, the effect of the weathering of young arc-related crust in the SW Pacific is an important source of unradiogenic Os to modern seawater.

Osmium isotope geochemistry of a tropical estuary

Abstract Fundamental aspects of the estuarine geochemistry of Os were investigated by analysis of the Os isotope composition and concentration variations in filtered water samples from a salinity transect taken in the estuary of the tropical Fly River of New Guinea. 187Os/188Os of the waters in the salinity transect increase with salinity from 0.6165 in the river endmember (0.1‰ salinity) to a maximum of 0.913 in the most saline water (33‰). These values are distinctly lower than the 187Os/188Os of 1.06 reported for open ocean waters from the Indian and Pacific Oceans Sharma et al 1997 , Levasseur et al 1998 , Woodhouse et al 1999 . The Os concentrations in the waters range from a minimum of 4.59 pg Os/g in the river to a maximum of 5.66 pg Os/kg at 12‰ salinity. These concentrations are all significantly lower than the open ocean range of 6.6 to 10.86 pg Os/kg Levasseur et al 1998 , Woodhouse et al 1999 . The isotopic results indicate that the rivers draining the New Guinea landmass provide unradiogenic dissolved Os to the oceans and led to a lowering of the 187Os/188Os of the local seawater. The Os concentration-salinity relationship indicates that the mixing process is not conservative and that removal of Os from the dissolved state has taken place. The proportion of Os lost from solution increases with salinity, resulting in removal of a large proportion of seawater Os in the estuary. High concentrations of Os in marine sediments within the Gulf of Papua were previously interpreted to be due to incorporation of seawater-derived Os into organic matter ( Martin et al., 2000 , Earth Planet. Sci. Lett.183, 261–274) and are the likely complement to the processes observed in the dissolved state. Enhanced removal of seawater Os in estuaries could help to resolve the differences in estimates of Os residence time made on the basis of oceanic deposits versus those based on measured river water concentrations.

Trophic importance of a temperate intertidal wetland to resident and itinerant taxa: evidence from multiple stable isotope analyses

Juveniles of commercially important fish species congregate in shallow vegetated estuarine habitats during high tides. Considerable debate has centred on whether the significance of these habitats lies in their provision of greater feeding opportunities, or shelter from predation afforded by greater structural complexity. We tested the hypothesis that an inundated mangrove and saltmarsh wetland provided feeding opportunities for itinerant species, and that the contribution of wetland primary producers and grazing herbivores could be identified in their diet, using stable isotopes of carbon and nitrogen. Potential sources of dietary carbon included mangrove, saltmarsh, seagrass, seagrass epiphytic material and benthic organic material. Saltmarsh plants (mostly Sporobolus virginicus and Juncus kraussii) and fine benthic organic material appeared to be the primary sources of dietary carbon for the resident grazing herbivores in the wetlands, based on IsoSource mixing models. During high tide, species of itinerant fish enter the mangrove and, when inundated, the saltmarsh, and feed primarily on crab larvae and copepods. Fine benthic organic matter, seagrass epiphyte, and C3 and C4 plant materials also supplement the diet of some fish. The crab larvae therefore provide a significant source of nutrition and an important link between the intertidal wetlands and the adjacent estuarine ecosystem. The carnivorous fish Acanthopagrus australis, at the highest trophic level, hunted within or adjacent to the mangrove–saltmarsh wetland and fed on several lower-order consumers within the wetland. The present study highlights the significance of mangrove and saltmarsh wetlands as a feeding habitat for resident grazers and itinerant nekton.

Variability of Stable Isotope Ratios of Glassfish (Ambassis jacksoniensis) from Mangrove/Saltmarsh Environments in Southeast Australia and Implications for Choosing Sample Size

Stable isotopes offer an accurate and cost-effective way to understand critical pathways of energy, and their use has application where aquatic habitats have been degraded. Isotope ratios can offer insights into appropriate conservation and rehabilitation techniques to manage these valuable resources. To date, the literature shows little attention to spatial and temporal variation in isotope signatures of samples taken from estuarine environments. This study reports on an investigation of sample size by which to determine isotopic signatures within a single species of fish, Ambassis jacksoniensis. Provided are two ways by which to determine how many samples are needed, and the results imply that care may be needed in interpreting previous studies based on small sample size. A minimum of five individuals would appear necessary in some cases.

Probabilistic Risk Assessment and Risk Mapping of Sediment Metals in Sydney Harbour Embayments

ABSTRACT Sediment metal concentrations in embayments of Sydney Harbour, acquired from the literature and from samples collected for this study, were used to generate contaminant probability density distributions using AQUARISK. The sediment metal concentrations often exceeded Australias interim sediment quality guidelines. Similarly, estuarine spiked sediment toxicity test literature provided adverse biotic effects concentration data to generate species sensitivity distributions using AQUARISK. Although the harbor is subject to other inorganic and organic contamination, we have used sediment metals to demonstrate an approach for ecological risk mapping and environmental management prioritization. Sufficient spiked sediment toxicity test data were found for only three metals—Cd, Cu, and Zn—and some tests were likely to overestimate toxicity. The estimates of the hazardous concentration to 5% of species (the 50th percentile of the 95% species protection level) were 5, 12, and 40 mg/kg DW of total sediment metal for Cd, Cu, and Zn, respectively. These values were generally low when compared with the interim sediment quality guidelines due to the overestimation of toxic effects in the literature data. The parameters for the species sensitivity distributions have been combined with the measured sediment metal concentrations in Homebush Bay to generate risk maps of the estimated species impact for each metal as well as for all three metals collectively assuming proportional additivity. This has demonstrated the utility of comparing contaminants on a consistent scale—ecological risk.

Biological properties of coral GFP-type proteins provide clues for engineering novel optical probes and biosensors

In recent years, a variety of Green Fluorescent Protein (GFP)-like pigments have been discovered from corals and other marine organisms. They are widely used to expand the range of available GFP-type proteins in imaging applications, such as in vivo markers for gene expression and protein localization studies, FRET-based (Förster resonance energy transfer) multicolor imaging and biosensors. They have known diverse optical and biochemical properties but their in vivo spectral properties and biological function in marine organisms is only beginning to be understood. We have investigated their spectral diversity, optical properties and cellular microstructure in corals of the Great Barrier Reef with the aim of elucidating their photo-biological function/s as well as to identify novel proteins suitable for GFP-based technologies. We found numerous spectral variants, with emissions covering almost the full range of the visible spectrum. Many of these GFP-like proteins, especially in corals from the more extreme habitats, such as sun-exposed shallows or in deep water, showed a range of light-related spectral characteristics: high photostability, spectral tuning for energy transfer and dynamic photo-induced transformation properties. Intra-cellularly they were organized into spectral donor-acceptor pairs or even arrays, tuned for FRET. Coral color proteins thus offer an exciting potential to expand the use of the available GFPs in bio-imaging applications and as a basis for improved protein engineering.

Application of synchrotron radiation technique to analysis of environmental samples

Synchrotron radiation experiments were performed at the Australian National Beamline Facility at Photon Factory, Tsukuba, Japan using the X-ray absorption near edge structure technique to investigate changes in redox speciation of iron and manganese in estuarine particles from the Fly River in Papua New Guinea. In low salinity samples manganese was mostly present as Mn(III) and Mn(IV) compounds with some surface-adsorbed Mn(II). Similarly, iron was present as Fe(III) and Fe(II/III) compounds with some adsorbed Fe(II). The proportions of both Mn(II) and Fe(III) significantly increased in higher salinity samples.

Correction to: Probabilistic risk assessment and risk mapping of metals in tropical estuarine sediments using the Aquarisk model

The original version of this article unfortunately contained a mistake in the article title.

Tools based on nuclear and isotopic techniques for the management of threatened coastal ecosystems

Elucidation of in situ environmental processes is the key to effective ecosystem management. However, due to the complexity of coastal ecosystems, few tools are available to determine the inter-relationships and rates of these events. It is only when all of the important variables are understood and computationally described that effective ecological risk analysis can be accomplished. Model packages already exist which describe and predict specific coastal processes and further refinement of subroutines and user-interfaces has some value; however the truly significant advances lie in synergistic integration of different codes. Predictive ecological risk analysis requires transport models predicting contaminant concentrations under a range of environmental scenarios and bioaccumulation and trophic-transfer models using keystone species (or critical groups) identified by models elucidating trophic structure. In an attempt to elucidate natural processes, or solve environmental problems, stable and radioisotope tracers have a number of advantages over conventional techniques. Stable isotope studies replace visual observations of prey-predator interactions with statistically interpretable chemical data. Radiotracers provide real time kinetic data on uptake and transfer of specific contaminants and environmental transport processes. The unique assemblage and application of these nuclear and isotopic environmental probes will greatly assist in effective ecological risk assessment of present situations and the resource-economic evaluation of proposed management options. The nuclear-based technologies developed from studies undertaken in the Sydney (Australia) environs are transferred to developing countries via the IAEA/Regional Cooperative Agreement (RCA) Project: Improving Regional Capacity for Assessment, Planning and Responding to Aquatic Environmental Emergencies (RAS/8/095). The IAEA Project objectives were to improve the regional capacity for the management of aquatic radiological and environmental risks and to develop capabilities in the RCA countries to assess, plan and respond to pollution events in aquatic environments. Expert missions supported national projects in individual Member States, further developing and transferring skills and technologies.