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Blooms of cyanobacteria in a temperate Australian lagoon system post and prior to European settlement
Get PDFBlooms of noxious N2 fixing cyanobacteria such as Nodularia spumigena are a recurring problem in some estuaries; however, the historic occurrence of such blooms in unclear in many cases. Here we report the results of a palaeoecological study on a temperate Australian lagoon system (the Gippsland Lakes) where we used stable isotopes and pigment biomarkers in dated cores as proxies for eutrophication and blooms of cyanobacteria. Pigment proxies show a clear signal, with an increase in cyanobacterial pigments (echinenone, canthaxanthin and zeaxanthin) in the period coinciding with recent blooms. Another excursion in these proxies was observed prior to the opening of an artificial entrance to the lakes in 1889, which markedly increased the salinity of the Gippsland Lakes. A coincident increase in the sediment organic-carbon content in the period prior to the opening of the artificial entrance suggests that the bottom waters of the lakes were more stratified and hypoxic, which would have led to an increase in the recycling of phosphorus. After the opening of the artificial entrance, there was a ˜ 60-year period with low values for the cyanobacterial proxies as well as a low sediment organic-carbon content suggesting a period of low bloom activity associated with the increased salinity of the lakes. During the 1940s, the current period of re-eutrophication commenced, as indicated by a steadily increasing sediment organic-carbon content and cyanobacterial pigments. We suggest that increasing nitrogen inputs from the catchment led to the return of hypoxia and increased phosphorus release from the sediment, which drove the re-emergence of cyanobacterial blooms
A medium-energy photoemission and ab-initio investigation of cubic yttria-stabilised zirconia
No full textExperimental and theoretical investigations into the electronic properties and structure of cubic yttria-stabilized zirconia are presented. Medium-energy x-ray photoemission spectroscopy measurements have been carried out for material with a concentration of 8-9 mol. % yttria. Resonant photoemission spectra are obtained for a range of photon energies that traverse the L2 absorption edge for both zirconium and yttrium. Through correlation with results from density-functional theory (DFT) calculations, based on structural models proposed in the literature, we assign photoemission peaks appearing in the spectra to core lines and Auger transitions. An analysis of the core level features enables the identification of shifts in the core level energies due to different local chemical environments of the constituent atoms. In general, each core line feature can be decomposed into three contributions, with associated energy shifts. Their identification with results of DFT calculations carried out for proposed atomic structures, lends support to these structural models. The experimental results indicate a multi-atom resonant photoemission effect between nearest-neighbour oxygen and yttrium atoms. Near-edge x-ray absorption fine structure spectra for zirconium and yttrium are also presented, which correlate well with calculated Zr- and Y-4d electron partial density-of-states and with Auger electron peak area versus photon energy curve. © 2014, AIP Publishing LLC
Geochemical investigation of the South Wellesley Island wetlands: Insight into wetland development during the Holocene in tropical northern Australia
No full textThe South Wellesley Islands in the Gulf of Carpentaria, northern Australia, were the recent focus of a palynological investigation which found vegetation change during the Holocene was driven by coastal progradation and regional climate. Here, we present new elemental data from x-ray fluorescence core scanning which provides non-destructive, continuous and high resolution analysis from three wetlands across Bentinck Island, the largest of the South Wellesley Islands. Elemental data and grain size analyses are combined with lead-210 (210Pb) and accelerator mass spectrometry (AMS) carbon-14 (14C) dates. An open coastal environment was present 1250 cal. a BP on the south east coast of Bentinck Island, with sediment supply incorporating fluvial deposition and detrital input of titanium and iron from eroding lateritic bedrock. Prograding shorelines, dune development and river diversion formed a series of swales parallel to the coast by ~800 cal. a BP, forming the Marralda wetlands. Wetlands developed at sites on the north and west coasts ~500 and ~450 cal. a BP, respectively. Geochemical and grain size analyses indicate that wetlands formed as accreting tidal mudflats or within inter-dune swales that intercepted groundwater draining to the coastal margins. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Elemental data provide new records of wetland development across Bentinck Island, highlighting the value of a multi-proxy approach to understanding environmental change during the Holocene in tropical northern Australia
Pleistocene occupation of Yellabidde Cave in the northern Swan Coastal Plain, southwestern Australia
No full textEvidence for human occupation of Western Australia’s northern Swan Coastal Plain derives mainly from Holocene coastal midden sites. Here, we present preliminary results from archaeological investigations at Yellabidde Cave, located 9 km inland from the present coast. Excavations in the limestone cave’s sandy floor deposit revealed cultural and palaeontological materials dating from c. 25,500 cal. BP to the 19th C. These provide the first evidence for Pleistocene occupation in the region, indicating that Yellabidde Cave was intermittently occupied throughout the late Pleistocene and Holocene, and reflecting dynamic human-environment relationships in present near-coastal to littoral environments
Relationship between damage and hardness profiles in ion irradiated SS316 using nanoindentation–Experiments and modelling.
No full textIn this work, the authors apply the “top-down” nanoindentation testing method to assess the mechanical property changes in ion-irradiated metallic alloys for three different ion energies in order to understand the relationship between ion energy, damage peak depth and hardness peak depth. The samples were irradiated with He+2 ions having 1, 2 and 3 MeV beam energies respectively. The curves for ΔH (radiation induced hardness) have been obtained by calculating the difference of the irradiated and unirradiated hardness curves after these were corrected for indentation size effect. Three-dimensional analytical and numerical models have been developed to obtain greater insight into the mechanisms involved in the nanoindentation processes, the nature of the plastic zone, and how these affect the hardness results, including the full hardness profiles with respect to depth. This is particularly valuable in situations where the damage profile is non-uniform, as in the present case, and provides the means to predict expected hardness peak positions and values for a given irradiation dose. Copyright © 2017 Elsevier B.V
Sydney Particle Study- Stage-II
Get PDFThe relationship between particle mass (as PM10 and PM2.5) and health outcomes such as decreased lung function, increased respiratory symptoms, increased chronic obstructive pulmonary disease, increased cardiovascular and cardiopulmonary disease, and increased mortality is now well established. This is well recognised by policy makers in Australia where the Council of Australian Governments has agreed that the initial focus of a new National Plan for Clean Air should be on particles, with the first stage of development being 1/ a health risk assessment; 2/ construction of an exposure reduction framework; 3/ development of emission reduction options and 4/ the undertaking of a cost benefit analysis. As such a quantitative understanding of the sources and sinks of particles within the target airsheds is an essential requirement for achieving the goals of the National Plan for Clean Air.
The NSW Office of the Environment and Heritage (OEH) has been pro-active in undertaking, in collaboration with CSIRO, ANSTO and QUT, the subject of this report- the Sydney Particle Study- comprising two field studies (conducted in February 2011 and April, May 2012), and a program of particle model development and application. During the field studies, observations of particles, particle precursor gases and other relevant environmental data were carried out at the Westmead Air Quality Station within the Sydney basin. The modelling task has seen the coupling of a three-dimensional gas-aerosol chemical transport model with the OEH air emissions inventory and the simulation of key particle processes identified by the field campaigns. The study will culminate with the provision of the data, modelling tools and associated training to the OEH air quality modellers, who will then be well placed to contribute aerosol modelling capability to the science and policy development required for the National Plan for Clean Air
Pollen, biomarker and stable isotope evidence of late Quaternary environmental change at Lake McKenzie, southeast Queensland.
No full textUnravelling links between climate change and vegetation response during the Quaternary is important if the climate–environment interactions of modern systems are to be fully understood. Using a sediment core from Lake McKenzie, Fraser Island, we reconstruct changes in the lake ecosystem and surrounding vegetation over the last ca. 36.9 cal kyr. Evidence is drawn from multiple sources, including pollen, micro-charcoal, biomarker and stable isotope (C and N) analyses, and is used to gain a better understanding of the nature and timing of past ecological changes that have occurred at the site. The glacial period of the record, from ca. 36.9 to 18.3 cal kyr BP, is characterised by an increased abundance of plants of the aquatic and littoral zone, indicating lower lake water levels. High abundance of biomarkers and microfossils of the colonial green alga Botryococcus occurred at this time and included large variation in individual botryococcene δ13C values. A slowing or ceasing of sediment accumulation occurred during the time period from ca. 18.3 to 14.0 cal kyr BP. By around 14.0 cal kyr BP fire activity in the area was reduced, as was abundance of littoral plants and terrestrial herbs, suggesting wetter conditions from that time. The Lake McKenzie pollen record conforms to existing records from Fraser Island by containing evidence of a period of reduced effective precipitation that commenced in the mid-Holocene. © Springer Science+Business Media Dordrecht 201
Nocturnal food webs: partitioning of prey resources between terrestrial and aquatic ecosystems by a high level predator of floodplain habitats
No full textWhen dry When dry floodplain systems flood, terrestrial predators (e.g. birds, lizards and spiders) can focus their diet on aquatic taxa reflecting a subsidy from the aquatic to the terrestrial ecosystem. Despite the abundance of bats on floodplains, little is known of how this high-level predator balances terrestrial and aquatic prey, particularly during periods of high energy demand (pregnancy and lactation). We used stable isotope analysis (δ13C & δ15N) to compare short and medium term diet of four functional groups of bats (aquatic trawler, mesic edge-space, ubiquitous gleaner and arid edge-space) with available terrestrial and aquatic prey during flooding of Barmah-Millewa Forest. We predicted that diet of bats in the medium term would reflect expected functional roles, while short-term diets would reflect a shift to aquatic prey during flooding, with a stronger shift for lactating females.
We found that aquatic trawlers and mesic edge-space bats foraged predominantly within aquatic habitats while ubiquitous gleaner and arid edge-space bats fed on terrestrial prey in both short and medium term diets. This may be due to size and echolocation call frequency constraints on the type of prey bats can forage on. Lactating females did not show a consistent preference for aquatic habitats but foraged at a higher trophic level than males for all groups, except the aquatic trawlers. This may reflect a more generalist strategy in lactating females, or in the case of aquatic specialists, potentially a constraint on foraging for higher trophic level prey, such as fish. systems flood, terrestrial predators (e.g. birds, lizards and spiders) can focus their diet on aquatic taxa reflecting a subsidy from the aquatic to the terrestrial ecosystem. Despite the abundance of bats on floodplains, little is known of how this high-level predator balances terrestrial and aquatic prey, particularly during periods of high energy demand (pregnancy and lactation). We used stable isotope analysis (δ13C & δ15N) to compare short and medium term diet of four functional groups of bats (aquatic trawler, mesic edge-space, ubiquitous gleaner and arid edge-space) with available terrestrial and aquatic prey during flooding of Barmah-Millewa Forest. We predicted that diet of bats in the medium term would reflect expected functional roles, while short-term diets would reflect a shift to aquatic prey during flooding, with a stronger shift for lactating females.
We found that aquatic trawlers and mesic edge-space bats foraged predominantly within aquatic habitats while ubiquitous gleaner and arid edge-space bats fed on terrestrial prey in both short and medium term diets. This may be due to size and echolocation call frequency constraints on the type of prey bats can forage on. Lactating females did not show a consistent preference for aquatic habitats but foraged at a higher trophic level than males for all groups, except the aquatic trawlers. This may reflect a more generalist strategy in lactating females, or in the case of aquatic specialists, potentially a constraint on foraging for higher trophic level prey, such as fish
Depth-resolved structural and compositional characterization of ion-implanted polystyrene that enables direct covalent immobilization of biomolecules
No full textA polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) to activate its surface for single-step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)–visible (vis) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characterization by FTIR, atomic force microscopy (AFM), ellipsometry, and X-ray reflectometry shows that polystyrene films modified in this way immobilize dense layers of protein (tropoelastin) directly from solution. A substantial fraction of the immobilized protein layer remains after rigorous washing with sodium dodecyl sulfate solution, indicating that its immobilization is by covalent bonding. © 2015, American Chemical Society
Chronometry of pedogenic and stratigraphic events from calcite produced by earthworms
No full textDating phases of pedogenesis, soil carbonate deposition or even the burial of whole soil profiles using 14C is a valuable goal in archaeology and pedology, but one that has been consistently hampered by the presence of old carbon skewing the measurements to produce apparent dates older than the true formation date. Calcite produced by earthworms could be a useful alternative source of datable carbon. Since earthworms both inhabit and ingest soils with an old carbon content, however, the granules could yield a 14C date older than the date of their formation. In this study, by examining granules from two sites of known-age stratigraphy, we show that the radiocarbon date derived from the granules' calcite closely reflects their true formation date, opening up the possibility of using the granules either individually or as distributions of dates to understand soil processes and date sealed archaeological layers. © 2015, Elsevier B.V