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Carbon and nitrogen stable isotope analysis of estuarine sediment cores has proved useful for tracing nutrient sources and for assessing changes to nutrient loading through time. However, this technique has rarely been applied to estuaries in the Southern Hemisphere, despite the vulnerability of urban estuaries to excess nutrient loading and eutrophication because of mounting anthropogenic pressures. This study uses sediment core nutrient concentrations (total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP)) and stable isotope analysis (δ13C, δ15N, and δ34S) in combination with lead-210 (210Pb) dating, to reveal information about past and current nutrient loads and sources to various parts of the Derwent estuary, Tasmania, Australia. The upper estuary was found to experience periods of low dissolved oxygen levels and δ13C and δ15N values indicate that the nutrient sources to the upper estuary are predominantly riverine inputs and pulp and paper mill effluent. The middle estuary was found to have higher nutrient (TN and TP) concentrations than other Australian estuaries (Quibray Bay, Woolooware Bay, and Moreton Bay). Along the whole estuary there was a transition of predominantly terrestrial OM in upper estuary to predominantly marine OM in middle/lower estuary. However, there was a clear influence from a nitrogen source with an enriched δ15N value, likely wastewater treatment plant (WWTP) effluent. 3-endmember mixing analysis between terrestrial OM, marine OM, and WWTP effluent shows that WWTP effluent has contributed to up to 30.9% of sediment composition in the past—highlighting the significance of anthropogenic nutrient inputs, such as waste-water treatment plant effluent, to an urban estuary. [ABSTRACT FROM AUTHOR]

Coastal systems such as estuaries are threatened by multiple anthropogenic stressors worldwide. However, how these stressors and estuarine hydrology shape benthic bacterial communities and their functions remains poorly known. Here, we surveyed sediment bacterial communities in poorly flushed embayments and well flushed channels in Sydney Harbour, Australia, using 16S rRNA gene sequencing. Sediment samples were collected monthly during the Austral summer-autumn 2014 at increasing distance from a large storm drain in each channel and embayment. Bacterial communities differed significantly between sites that varied in proximity to storm drains, with a gradient of change apparent for sites within embayments. We explored this pattern for embayment sites with analysis of RNA-Seq gene expression patterns and found higher expression of multiple genes involved in bacterial stress response far from storm drains, suggesting that bacterial communities close to storm drains may be more tolerant of localised anthropogenic stressors. Several bacterial groups also differed close to and far from storm drains, suggesting their potential utility as bioindicators to monitor contaminants in estuarine sediments. Overall, our study provides useful insights into changes in the composition and functioning of benthic bacterial communities as a result of multiple anthropogenic stressors in differing hydrological conditions. [ABSTRACT FROM AUTHOR]

Arcid cockles support extensive subsistence, recreational and commercial fisheries across the world. In south-eastern Australia, there is minimal published research and a lack of quantitative surveys for the primary harvested species, Sydney Cockle Anadara trapezia , with which to inform management of the resource. Here, we describe the modification and application of an off-the-shelf lightweight recreational scallop dredge for conducting scientific surveys of arcid clams in estuarine soft sediment habitats. Specifically, we look at performance of the gear for sampling medium-large (>45 mm shell length) cockles, and report on the outcomes of preliminary trials of the gear for surveying Sydney Cockle. Efficiency trials showed that the gear captured and retained ∼95% of the cockles in the tow path, however efficiency decreased in compacted sediments (∼66%). Trial surveys captured cockles between 33 and 78 mm shell length, at densities as high as 186 individuals 100 m−2. The modified scallop dredge provides a robust and portable (∼10 kg weight) fishing gear for sampling estuarine soft sediment habitats from small vessels. Both the sampling gear, and the methodology presented here, are broadly applicable for surveying arcid cockles and other bivalve species from similar soft sediment habitats elsewhere. • An off-the-shelf recreational scallop dredge is modified for sampling arcid clams. • The modified dredge sampled the target size range with 66–95% efficiency. • Lightweight but robust construction make the dredge ideal for use from small boats. • In a pilot survey, cockles were captured at densities up to 186 individuals 100 m−2. [ABSTRACT FROM AUTHOR]

Agriculture activities in coastal catchments often contribute pollutant runoff such as nitrogen (N), phosphorus (P), and trace metals to estuarine environments. Here, we determine the historical impacts from agricultural expansion using sediment samples from an estuary and a coastal wetland downstream from intensive historical banana, and now, blueberry plantations (Hearnes Lake estuary, NSW, Australia). The three 210Pb dated sediment cores and surface sediment samples analyzed in this study revealed that trace metals (As, Cd, Cu, Pb, Zn, Cr) and N fluxes recently increased as a result of increasing sedimentation rates. Several moderate localized enrichments were observed in recent sediment layers. Most importantly, we found a clear link between the sediment P profile and recent blueberry cultivation. P enrichment increased by 9-fold and sediment fluxes by over 40-fold (up to 12.6 mg m−2 year−1) during the expansion of blueberry cultivation within the catchment since 2002. The trapping of sediments enriched in P by the wetlands provided a good chronology of agricultural practices in the region. With a global and regional increase in estuarine eutrophication, this study further demonstrates the importance of agricultural sources and the role coastal wetlands play in sequestering P from runoff. [ABSTRACT FROM AUTHOR]

Novel combinations of climatic conditions due to climate change and prolonged fire seasons have contributed to an increased occurrence of "megafires". Such large-scale fires pose an unknown threat to biodiversity due to the increased extent and severity of burn. Assessments of wildfires often focus on terrestrial ecosystems and effects on aquatic habitats are less documented, particularly in coastal environments. In a novel application of eDNA techniques, we assessed the impacts of the 2019–2020 Australian wildfires on the diversity of estuarine benthic sediment communities in six estuaries in NSW, Australia, before and after the fires. Estuaries differed in area of catchment burnt (0–92%) and amount of vegetative buffer that remained post-fire between burnt areas and waterways. We found greater dissimilarities in the composition and abundance of eukaryotic and bacterial sediment communities in estuaries from burnt catchments with no buffer compared to those with an intact buffer or from unburnt catchments. Shifts in composition in highly burnt catchments were associated with increased concentrations of nutrients, carbon, including fire-derived pyrogenic carbon, and copper, which was representative of multiple highly correlated trace metals. Changes in the relative abundances of certain taxonomic groups, such as sulfate-reducing and nitrifying bacterial groups, in the most impacted estuaries indicate potential consequences for the functioning of sediment communities. These results provide a unique demonstration of the use of eDNA to identify wildfire impacts on ecological communities and emphasize the importance of vegetative buffers in limiting wildfire-associated impacts. [Display omitted] • Estuarine benthic eukaryotic and bacterial community composition changed post-fire. • Greater differences were observed in severely burnt compared to unburnt catchments. • Changes were associated with increased sediment py-C, TOC, Cu and nutrients. • Shifts in certain bacterial groups may have implications for sediment functioning. • EDNA is a useful tool for rapid assessment of wildfire impacts in aquatic systems. [ABSTRACT FROM AUTHOR]

Estuaries are critical habitats subject to a range of stressors requiring effective management. Microbes are gaining recognition as effective environmental indicators, however, the response of host associated communities to stressors remains poorly understood. We examined microbial communities from seawater, sediments and the estuarine fish Pelates sexlineatus , in Australia's largest urbanised estuary, and hypothesised that anthropogenic contamination would be reflected in the microbiology of these sample types. The human faecal markers Lachno3 and HF183 were not detected, indicating negligible influence of sewage, but a gradient in copy numbers of the class 1 integron (intI-1), which is often used as a marker for anthropogenic contamination, was observed in sediments and positively correlated with metal concentrations. While seawater communities were not strongly driven by metal contamination, shifts in the diversity and composition of the fish gut microbiome were observed, with statistical links to levels of metal contamination (F 2, 21 = 1.536, p < 0.01). Within the fish gut microbiome, we further report increased relative abundance of amplicon sequence variants (ASVs; single inferred DNA sequences obtained in sequencing) identified as metal resistant and potentially pathogenic genera, as well as those that may have roles in inflammation. These results demonstrate that microbial communities from distinct habitats within estuarine systems have unique response to stressors, and alterations of the fish gut microbiome may have implications for the adaptation of estuarine fish to legacy metal contamination. [Display omitted] [ABSTRACT FROM AUTHOR]

Saintilan, N.; Rogers, K.; Toms C. Stein, E.D., and Jacobs, D.K., 2016. Intermittent Estuaries: linking Hydro-geomorphic Context to Climate Change Resilience In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 133-137. Coconut Creek (Florida), ISSN 0749-0208. Intermittent estuaries are temporarily open to exchange with the open ocean, and the influence of their entrance opening regime on hydrological and ecological function has received considerable attention. Here we consider the influence of tectonic, climatic and geomorphic controls on the distribution of estuarine habitats by contrasting two settings: the south coasts of New South Wales, Australia, and California USA. The combination of tectonic uplift and semi-arid, variable hydrology in southern California provides a stronger sediment yield to estuaries than in the tectonically stable temperate setting of southern Australia. This reflects in a greater proportional area of intertidal vegetation and a higher elevation capital than encountered in SE Australia. The implications for estuary management in the context of sea-level rise and urbanization are discussed. [ABSTRACT FROM AUTHOR]

The distribution, composition, density, and biomass of benthic macrofauna within estuarine environments typically exhibit significant variations attributable to heterogeneity in and interactions between physical, biological, and chemical processes. The spatial and temporal dynamics of benthic macroinfauna assemblages and physicochemical sediment parameters within the intertidal mudflats of a subtropical estuarine lake (Coombabah Lake, Southern Moreton Bay) were studied at four sites from August 2006 to April 2007. No significant seasonal changes were observed at any site for all physical sediment parameters. The northern sample sites were characterised by fine- to medium-grained to moderately to poorly sorted sediments and the southern sample sites by fine-grained to moderately well to well-sorted. A total of 1029 individuals representing species from three orders, including deposit feeding and filter feeding macroinfaunal groups, were collected. The highest combined species densities occurred in the fine-grained southern sites, with the greatest combined species density occurring at Site 4 during winter. Amphipods (Victoriopisa australiensis) and polychaete worms (Simplisetia aequisetis) dominated the lake-wide faunal community with V. australiensis, representing 49% of the total retrieved macroinfauna. Significant correlations between mean macro-infauna densities, biomassow, sediment parameters, and seasonal maximum monthly temperatures were identified during the study. Seasonal trends in combined site densities were observed at each of the lake sites, with the highest combined density occurring during winter. Spatial and temporal variations might also be partially explained by the prédation pressures of fish and migratory wading birds within the lake, with the seasonal presence of migratory wading birds coinciding with the minimum observed macroinfauna densities at each sample site. [ABSTRACT FROM AUTHOR]

Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO2. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney - the site of European settlement of Australia - to look for human-induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (~6000 years) according to 210Pb profiles and radiocarbon ( 14C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 30-50 years were considerably higher than during the rest of the Holocene. C : N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of 12C/ 13C showed that the relative contribution of seagrass and C3 terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (~1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication. Given the lower carbon burial efficiencies of microalgae (~0.1%) relative to seagrasses and C3 terrestrial plants (up to 10%), such changes represent a substantial weakening of the carbon sink potential of Botany Bay - this occurrence is likely to be common to human-impacted estuaries, and has consequences for the role these systems play in helping to mitigate climate change. [ABSTRACT FROM AUTHOR]

In this study, we combined grain size and geochemical analyses with radioisotope analysis of lead-210 (Pb), caesium-137 (Cs) and radiocarbon (C) ages to reconstruct the sedimentation history of two urbanised coastal lagoons in south-east Australia. Towradgi and Fairy Lagoons were both found to exhibit slow initial sedimentation of less than 1 mm year prior to anthropogenic influences. Land clearing in the catchments increased runoff and erosion in the creeks feeding into the estuaries, and has resulted in progradation of fluvial material into the estuarine systems with a marked increase in sedimentation to between 2 and 7 mm year. The upper 20-50 cm of the sediment column in both lagoons contained elevated concentrations of heavy metals such as Pb, Cu, Ni and Zn. This pollution trend was found to be consistent with the history of industrialisation and urbanisation in the region, which expanded rapidly post World War 2. The total metal concentrations were consistent with other urbanised/industrialised estuaries around the world. Despite the fairly disturbed nature of these coastal lagoons, the use of Pb, Cs and C dating in combination with bulk geochemical analyses allowed detailed reconstruction of sedimentation history. [ABSTRACT FROM AUTHOR]

Abstract: We assess species composition, assemblage structure and distribution of the benthic foraminiferal assemblages from diverse substrates in Moreton Bay, South-East Queensland, Australia. Analysis of 47 surface sediment samples revealed 69 species, three distinct foraminiferal assemblages and six sub-assemblages. The assemblages from the western Bay are characterized by stress tolerant taxa and the lowest diversity, whereas the assemblages from the eastern Bay are characterized by symbiont-bearing taxa and high diversity. We found a correlation between foraminiferal assemblages and substrate conditions that was indicative of strong environmental gradients (substrate type, water quality and salinity), from an urban-impacted assemblage in the westernmost part of the Bay, to a hyposaline, estuarine-influenced assemblage in the western Bay to a nearly normal marine to hypersaline assemblage in the eastern Bay. The FORAM Index was consistent with the changes in water and sediment quality gradient, from the western shoreline to the eastern Bay. Thus the foraminiferal assemblages of Moreton Bay make excellent bio-indicators of environmental changes in a subtropical, estuarine setting in eastern Australia. [ABSTRACT FROM AUTHOR]

The influence of natural populations of the sub-surface deposit-feeding amphipod Victoriopisa australiensis on sediment biogeochemistry was assessed by randomly collecting 21 sediment cores in a zone of Coombabah Lake, southern Moreton Bay, Australia, where the benthic infauna was dominated by this species. Cores were incubated sequentially to determine sediment–water column fluxes of oxygen, dissolved inorganic carbon and inorganic N species, followed by incubations to determine rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) using the isotope pairing technique. Finally, each core was sieved in order to determine the population and biomass of amphipods present. Whilst all measures of overall benthic metabolism (sediment oxygen demand, and effluxes of inorganic carbon and nitrogen) showed increased with amphipod density, with rates being stimulated 70–220% at the highest categorised density range of 2,500–3,500 ind m−2, only the correlation with dissolved inorganic carbon was statistically significant. In contrast, there were no discernable trends between amphipod densities and any of the N-cycle processes with the slopes of all correlations being very close to zero. These results highlight the differences in mesocosm simulations of fauna effects, which primarily relate to shifts in rates of organic matter turnover, compared to natural sediments where fauna effects relate more to induced changes in rates of organic matter deposition. Therefore, while mesocosms represent a powerful tool to investigate the mechanisms by which fauna influences microbial metabolism in the sediment, only studies of natural sediments can determine to what extent these mechanisms function in situ. [ABSTRACT FROM AUTHOR]

Like many other coastal systems across the world, the Coorong lagoonal ecosystem (South Australia) has degraded over the last 100 years; in this case as a result of extensive regulation and diversions of water across the Murray-Darling Basin following European settlement. To evaluate whether the sources of organic matter (OM) supporting its food-web have changed since the inception of water management and barrage construction, sedimentary OM was characterised in cores spanning the Coorong’s salinity gradient at depths representative of the last 100 years over which the management alterations to river and estuarine flow were most marked. Detailed 210Pb, 137Cs and Pu dating in conjunction with palaeolimnological data ( Pinus pollen) allowed for the reconstruction of the timing of substantial changes observed in the composition of the OM, most of which occur during the early 1950s, concurrent with management-related variations in water flow and salinity. Negative shifts in δ13C of up to 8.3‰ in the 2–10 and <2 μm fractions after the 1950s suggest a pronounced alteration in biogeochemical cycling or in the origin of OM. Elemental ratios and δ13C values of potential sources are inconclusive as to the cause of these biogeochemical changes. However, 13C-NMR spectra of the sediments suggest that degraded phytoplankton constitutes a large proportion of today’s OM and also reveal that an OM source rich in lignin was present prior to the 1950s. The high δ13C (−18.3‰) and low C/N (7.5) signatures of the lignin-bearing sediments are inconsistent with a C3 terrestrial OM source and instead suggest that the lignin-bearing seagrass Ruppia megacarpa (δ13C of −13‰) contributed to a large degree to the sediment of the North Lagoon. R. megacarpa once was abundant in the North Lagoon but today has all but vanished from the system. Thus, only through a combination of isotopic and spectroscopic techniques was it possible to effectively decipher the changes in the composition of OM deposited throughout the Coorong over space and time. These results have important implications for research in estuarine OM dynamics in other geographic locations. Specifically, utilising complementary analytical techniques may sometimes be essential in reliably determining OM sources and processes in estuaries and lagoons. [ABSTRACT FROM AUTHOR]

A sediment compartment approach is an appropriate framework within which to undertake planning and management of coastal environments, and a hierarchical scheme has been adopted by several state governments in Australia. This study applies a geospatial comparison of terrain modelling to estimate decadal-scale sediment transfer in a closed wave-dominated coastal compartment in southeastern Australia. The Shoalhaven River, one of the larger rivers in southern New South Wales, drains from a temperate catchment of 7151 km2 into Shoalhaven Bight, a secondary compartment. The river has infilled the barrier estuary at its mouth in recent millennia, and delivers sediment that nourishes a well-developed strandplain to its north. We estimate sediment yield from the heterogeneous catchment based on deposition between 2003 and 2014 bathymetric surveys in a reservoir formed as a result of dam construction. Delivery of ~86,000 m3/y to the estuarine channel was calculated, adopting a known trap efficiency at the dam, augmented by sediment from a further unmodified tributary. Volumetric change of the estuary and adjacent nearshore was determined by comparison of surveys in 1981 and 2006. A complex pattern of estuarine surficial sediments reflects modification of the river's natural course, which is now artificially diverted to exit at Crookhaven Heads. During major flood events, the river intermittently discharges material to the shoreface at Shoalhaven Heads, its former mouth, which is impounded again by deposition of a sandy berm in the months following such storms. Between 1981 and 2006, at least 1,020,000 m3 was added to the estuary, and 1,065,000 m3 of sand was discharged to the shoreface. Sand sourced from the Shoalhaven River is retained within the northernmost of three tertiary compartments, Seven Mile Beach, as cliffed headlands and rocky reefs restrict along-shore sediment contributions from the south and inhibit leakage to the north. Balance of the budget based on shoreline accretion during 41 years is consistent with cross-shore transport and an ongoing shoreface supply rate of 1–2 m3/m/y. Although a number of uncertainties constrain the final sediment budget, with complex patterns of erosion or accretion in response to natural events or engineering interventions, this preliminary study indicates the potential for deriving decadal-scale estimates of sediment pathways and transfer rates using geospatial analysis of terrain changes, which can provide a basis for planning and management actions. • The Shoalhaven River infilled an estuary and delivers sand to its coastal compartment. • River sand, after minor estuarine deposition, augments sand from the shoreface • During major floods the river intermittently deposits a sandbar offshore of its mouth. • Redistribution of fluvial sand alongshore nourishes a strandplain to the north. • Decadal volume change indicates sediment transfers as basis for planning. [ABSTRACT FROM AUTHOR]

This study presents the first measurements of anthropogenic plutonium (239Pu and 240Pu) concentrations and atom ratios (240Pu/239Pu) for Tasmania, in sediment collected from Bathurst Harbour, in the Tasmanian Wilderness World Heritage Area, Australia. The weighted mean 240Pu/239Pu atom ratio measured at this site was 0.172 ± 0.007 which is consistent with published data from mainland Australia and global and Southern Hemisphere averages. The 240Pu/239Pu atom ratios ranged between 0.11 and 0.21 with the earliest recorded 240Pu/239Pu atom ratios being the lowest, suggesting an influence of low atom ratio fallout from nuclear testing in Australia. Post-moratorium fallout 240Pu/239Pu atom ratios were consistent with other records. Lead-210 (210Pb) sediment chronologies indicate sediment accumulation rates have increased since the early part of the 19th century at this location. [Display omitted] • Presents the first measurements of fallout plutonium concentrations and 240Pu/239Pu atom ratios in Tasmania, Australia. • Uses an estuarine sediment record from a World Heritage Area to reconstruct fallout from global nuclear weapons testing. • Early 240Pu/239Pu atom ratios indicate contribution of fallout from British testing in Australia. [ABSTRACT FROM AUTHOR]

Abstract: Extensive physical and biological measurements were made of the surface sediments within the shallow, semi-urbanised Coombabah Lake in southern Moreton Bay, Australia. Sediment bulk parameters (C/N ratios, δ 13C and δ 15N) and fatty acid biomarkers were used to determine distributions and sources of organic matter in the intertidal sediments. The determination of organic matter sources within coastal and estuarine settings is important in understanding the roles of organic matter as energy and nutrient sources. Spatial variability of biomarker values within the sediments were interpreted by thematic maps employing the Krigging algorithm. Grain size analysis indicated the lake was dominated by mud (<63μm) in the southern (landward) and sand (>63μm) in the northern (seaward) lake regions, respectively. Surface sediment organic C and N values ranged from 0.12% to 1.76% and 0.01% to 0.12% dry weight, respectively, and C/N ratios averaged 16.3±3.19%. Sedimentary δ 13C values ranged from −26.1‰ to −20.9‰, with an average value of −23.9±1.0‰. Sedimentary δ 15N values ranged from +1.7‰ to +4.8‰, with an average value of +2.8±0.8‰. Bulk sediment parameters suggested that sedimentary organic matter is provided predominantly by allochthonous sources in the form of fringing mangroves. Thirty-nine individual fatty acids were identified using gas chromatography–mass spectrometry. The mean contributions of long chain fatty acids (LCFAs), polyunsaturated fatty acids (PUFAs), saturated fatty acids (SAFAs) and bacterial fatty acids (BAFAs) were, respectively, 13.9±11.4%, 7.6±4.1%, 53.6±8.6% and 18.2±4.6% of the identified fatty acid methyl esters (FAMEs), with BAFAs occurring in all sampled sediments. Fatty acid compositions varied throughout lake sediments, which indicated spatial differences in autochthonous and allochthonous organic matter sources, including terrestrial and planktonic (i.e. zooplankton, diatoms and other algal species) sources. The contribution of organic matter from shoreline mangroves was confirmed by the presence of LCFAs and 18:2ω6 and 18:3ω3, which are markers for mangroves in this ecosystem. BAFAs were identified in increased proportions in sediments adjacent to urban developments and dominated by mud. Grain size was identified as a dominant factor in the fatty acid compositions and contributing values to FAME pool. Spatial patterns of C/N ratios, δ 13C and δ 15N values, and fatty acid biomarker contributions illustrated that there is a greater contribution of autochthonous and labile organic matter to the sedimentary organic matter pool in the northern (marine entrance) sediments compared to the more allochthonous sourced organic matter of the southern region of the lake. This study details the distribution and sources of organic matter within Coombabah Lake and illustrates the usefulness of a multiple biomarker approach in discriminating organic matter sources within estuarine environments. [Copyright &y& Elsevier]

Abstract: Strontium isotope data indicate that sediments of the Norwest Bend Formation were deposited within a large estuarine system during the Latest Miocene to Early Pliocene (probably > 5 Ma). The Norwest Bend Formation is divisible into two members; a lower sand-dominated member and an upper oyster coquina member. These two units are separated by an irregular, erosion surface that has no correlative within the adjacent Loxton–Parilla Sands. Tectonism in the western Murray Basin adjacent to the Adelaide Foldbelt has exerted a considerable control over the formation of these estuarine sediments. The Lower Norwest Bend Formation occupies a paleodrainage system that was restricted to a region west of the Hamley Fault and was presumably incised following uplift of this western block. Flooding of this paleodrainage system produced the Lower Norwest Bend estuarine system. Later tectonism on the Hamley Fault resulted in the formation of the erosion surface within the Norwest Bend Formation. We suggest that the Norwest Bend estuarine system owes its existence to marginal tectonism associated with the young uplift of the Mt. Lofty-Flinders Ranges. The paleodrainage system incised prior to deposition of the Norwest Bend Formation differs markedly in geometry from the present Murray River-gorge system. This suggests that the modern Murray River system developed after deposition of the Late Miocene–Pliocene Norwest Bend Formation. [Copyright &y& Elsevier]

This study examined the potential use of macroalgae epiphytic on mangrove aerial roots as biomonitors of estuarine contamination. The metal concentrations of macroalgae were investigated in four estuaries in the vicinity of Sydney, Australia, and compared to water and sediment metal concentrations over three seasonal surveys. Macroalgal metal concentrations (copper, zinc, cadmium, chromium, lead, nickel, manganese and iron) appeared to be more associated with sediment metal concentrations than water concentrations, suggesting they may be useful biomonitors of estuarine sediment contamination. Algae in the more contaminated estuaries generally contained higher metal concentrations. However, concentrations of iron, nickel and manganese appeared to be similar in the algae despite the varying sediment concentrations, while accumulation of copper, zinc, lead and chromium appeared to be associated with ambient environmental concentrations. The uptake of metals also varied among the different species, suggesting that algal parameters, such as morphology, may also influence metal uptake and accumulation. [Copyright &y& Elsevier]

This investigation revealed the presence of traffic-derived metals within road, stream and estuarine sediments collected from a coastal catchment, northern Australia. Studied road sediments displayed variable total metal concentrations (median Cd, Cu, Pb, Pd, Pt, Ni and Zn values: 0.19, 42.6, 67.5, 0.064, 0.104, 36.7 and 698 mg/kg, respectively). The distinctly elevated Zn values are due to abundant tyre rubber shreds (as verified by SEM-EDS and correlation analysis). By comparison to the road sediments, background stream sediments taken upstream from roads have relatively low median Pb, Pd, Pt and Zn concentrations (7.3 mg/kg Pb, 0.01 mg/kg Pd, 0.012 mg/kg Pt, 62 mg/kg Zn). Stream and estuarine sediment samples collected below roads have median values of 21.8 mg/kg Pb, 0.014 mg/kg Pd, 0.021 mg/kg Pt and 71 mg/kg Zn, and exhibit 207Pb/206Pb and 208Pb/206Pb ratios that appear on a mixing line between the isotopically distinct background stream sediments and the road sediments. Thus, mobilisation of dusts and sediments from road surfaces has resulted in relatively elevated Pb, Pd, Pt and Zn concentrations and non-radiogenic Pb isotope ratios in local coastal stream and estuarine sediments. The investigation demonstrates that traffic-derived metals enter coastal stream and estuary sediments at the fringe of the Great Barrier Reef lagoon. [ABSTRACT FROM AUTHOR]

This study addresses the mid- to late Holocene stratigraphy and sea level history of a macrotidal barrier and paleoestuary system located along the relatively unstudied northwest coast of Australia. Thirty-nine shallow cores were obtained from three transects perpendicular to the barrier and paleoestuary axis. Seven sedimentary facies were identified on the basis of sediment texture, carbonate content, and foraminifera assemblages: slope, upper intertidal mud, upper intertidal sand flat, lower intertidal sand flat, barrier, estuarine beach, and flood tide delta. The sedimentary infill reveals a fining upward succession of marine sediments up to 6 m thick, mostly along a regressive sequence. All facies are of Holocene age and started to be laid down when sea level was approximately 3 m below present elevation. A radiocarbon date from the topmost sedimentary facies (upper intertidal mud) indicates that relative sea level was at least 1 m higher than today by 2720 years BP. At this time, the estuary was at the final stages of sedimentary infill, with tidal inundation reduced to a minimum. Further evidence of a higher relative sea level during the Holocene is in the form of estuarine beach deposits found at the back of the paleoestuary at an elevation above the present day beach/dune interface. Net nearshore transport in the area, driven by tidal current asymmetry, is northward, and it is proposed that this has significantly influenced the alongshore component of the barrier progradation and evolution of the barrier estuary. [ABSTRACT FROM AUTHOR]

The distribution and enrichment of selected trace metals (Cd, Cr, Cu, Ni, Pb, Sn, Zn) in benthic sediments of the Southport Broadwater, a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia, was studied with the objective of assessing the extent and degree of sediment contamination. Sediment samples from the 0–10 cm and 10–20 cm depth intervals of 32 sites within the Southport Broadwater and surrounding residential canals were analysed for particle size distribution, pH, organic C and ‘near-total’ major (Al, Ca, Fe, Mn) and trace (Cd, Cr, Cu, Ni, Pb, Sn, Zn) metal contents. Sediment contamination for each trace metal was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical normalisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, the results indicate that submerged sediments in the study area are not presently enriched with Cd, Cr or Ni, with the spatial distribution of these metals being very well explained by the abundance of alumino-silicate clay minerals. However, several sites were strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The study indicates that several varying approaches are needed for a satisfactory assessment of contaminant enrichment in estuarine sediments. [ABSTRACT FROM AUTHOR]

This paper focuses on the distribution of 137Cs and 210Pbxs in 51 estuarine and marine sediment cores collected between the Upstart Bay and Rockingham Bay in the Great Barrier Reef Lagoon, north-eastern Australia. Historical records of 210Pbxs and 137Cs atmospheric deposition and present day terrestrial inventories in north-eastern Australia are presented. 210Pbxs and 137Cs fluxes measured on suspended sediments in the Burdekin River are considered to be a source of recent inputs of these nuclides to the nearshore region of this part of the Great Barrier Reef. Direct correlations between sediment nuclide inventories, maximum detectable depths, and sediment mass accumulation rates (MARs), calculated using both 137Cs and 210Pbxs, are explored. In relation to inventories of 210Pbxs, 60% of atmospheric fallout 137Cs appears to be missing from the sediments. The reasons for these differences in two tracers, primarily of atmospheric origin, are discussed in terms of the geochemical properties of these two nuclides. Evidence is presented to support the hypothesis that the 137Cs distribution in these cores can be a useful independent tracer which provides confirmation of MARs calculated from the decay of 210Pbxs. [Copyright &y& Elsevier]

Estuarine systems adjacent to urban areas are at risk of contamination by contaminants from anthropogenic sources, such as heavy metals. We anticipated that the sediments of the Swan River estuary, which runs through metropolitan Perth in Western Australia, would show metal contamination related to industrialization and inputs of stormwater. Total Cu, Pb and Cd concentrations, and Cu, Pb, Cr and Zn in operationally-defined fractions, were determined in separate sampling exercises in near-shore sediments of the upper Swan River estuary. Total metal concentrations in sediments were not high (maximum values of 297 mg kg-1 for Cu, 184 mg kg-1 for Pb and 0.9 mg kg-1 for Cd) when compared with Australian environmental assessment guidelines for soils. On the basis of linear regressions between sediment metal concentrations and physicochemical properties of the sediments (pH, organic carbon, particle size distribution), no single parameter could explain the variation in metal concentrations for all metals. Sediment organic carbon content was positively correlated with Cu concentration; Cu concentrations also increased significantly with increasing clay content and decreasing sand content. Pb concentrations showed a significant increase with increasing sediment pH, and were approximately three-fold higher in sediments adjacent to stormwater drain outfalls than in sediments remote from drains; no such effect was observed for Cu or Cd. No effect of distance downstream was observed. Sequential extraction of sediments showed that most of the metals were in relatively immobile forms, for example bound to Fe oxides, or only extractable by aqua regia. The enhanced concentrations of Pb near stormwater outfalls suggest that vehicle-derived Pb may be an important contributor of Pb to the estuary. [ABSTRACT FROM AUTHOR]

Port Hacking is a tide-dominated, drowned river valley at the southern edge of the Sydney conurbation (Australia) and is bordered by intense urbanization to the north and native bushland in the south. The current work provides a first-time, baseline evaluation of the magnitude of human-induced change and risk posed by sedimentary metals in Port Hacking and catchment. The estuary separates fluvial and estuarine sediment enriched in metals exhibiting moderate ecological risk from sediments with minimal anthropogenic change and no biological risk. A full set of baseline data is provided in support of new monitoring of recent and future anthropogenic impacts on the system. • Port Hacking estuary separates intense urbanization from pristine bushland. • First baseline evaluation of anthropogenic change and ecological risk posed by sedimentary metals • Estuary separates metal-enriched sediment with moderate ecological risk from sediments with no ecological risk. • Full set of baseline data is provided in support of new monitoring of future anthropogenic impacts. [ABSTRACT FROM AUTHOR]

This study aimed to determine the prevalence and abundance of sewage and animal fecal contamination of sediment at seven estuarine locations in Sydney, NSW, Australia. Sediment samples were tested for the occurrence of microbial targets including molecular marker genes of enterococci (ENT), Bacteroides HF183 (HF183), Methanobrevibacter smithii (nifH) , human adenovirus (HAdV) and emerging sewage-associated marker genes crAssphage (CPQ_056) and Lachnospiraceae (Lachno3) and animal feces-associated marker genes, including avian feces-associated Helicobacter spp. (GFD), canine-feces associated Bacteroides (DogBact), cattle-feces associated (cowM2) and horse feces-associated Bacteroides (HoF597). Results from this study showed that urban estuarine sediment can act as a reservoir of fecal indicator bacteria (FIB) and several microbial source tracking (MST) marker genes, including previously unreported Lachno3. The sewage-associated marker gene CPQ_056 was most prevalent, in 63.8% of sediment samples, while the avian associated marker gene GFD had the highest mean abundance. The GFD marker gene was highly abundant and widely detected in sediment samples from all seven locations compared to the other animal feces-associated marker genes. In all, 31 (44.9%) sediment samples were positive for at least two sewage-associated marker genes. However, the non-quantifiable detection of the HAdV marker gene did not always align with the detection of two or more sewage-associated marker genes. In addition, the most frequent wet weather overflow exposure occurred at locations that did not have a consistent pattern of detection of the sewage-associated marker genes, suggesting sediments may not be a suitable measure of recent sewage contamination. To assist water quality and public health managers better understand past microbial contamination of estuarine sediment, further studies seem justified to explore the role of decay of MST marker genes in sediment. Further work is also needed on the role of resuspension of MST marker genes from sediment during storm events to the water column as a source of contamination for both the GFD and sewage-associated marker genes. • The crAssphage marker gene was detected in 63.8% of sediment samples. • The avian marker was highly abundant and widely detected in sediment. • Adenovirus did not always align with the detection of two or more sewage markers. • The prevalence of the sewage marker genes did not align well with wet weather overflows. [ABSTRACT FROM AUTHOR]

Great ecological and human health risks may arise from the presence of polycyclic aromatic hydrocarbons (PAHs) in aquatic environments and particularly in sediments, where they often partition. In spite of the apparent risk, knowledge about PAHs and their polar derivatives in sediments is limited. We, therefore, carried out an assessment of the concentrations of parent PAHs and their derivatives (polar PAHs) in sediments of Lake Macquarie: the largest saltwater lake in the southern hemisphere. A total of 31 sediment samples along the pollution prone western shoreline of the estuary were analysed. Multiple source apportionment methods were used to investigate PAH sources contributing to parent and polar PAH concentrations in the estuarine sediments. Concentration levels were highest for high molecular weight (HMW) PAHs compared to low molecular weight (LMW) PAHs. The highest PAH concentrations were recorded for oxygenated PAHs (oxy-PAHs) compared to parent and other polar PAHs. Polycyclic aromatic hydrocarbon diagnostic ratios and compositional analysis showed that PAHs in Lake Macquarie were predominantly pyrogenic exhibiting strong positive correlation (R2 = 0.972) with total PAH concentrations. Principal Component Analysis (PCA) identified three groupings of PAHs with oxy-PAHs and NPAHs dominating (40.2%). Carbazole, a heterocyclic PAH, was also a prominent contributor to sediment PAH concentrations. Atmospheric deposition, coal combustion and vehicular emissions were implicated as the major contributors to sediment pollution. Image 1 • Parent and polar PAH concentrations of Lake Macquarie sediment were assessed. • Sediment oxy-PAH concentrations were highest compared to other PAHs. • Compositional and multivariate analysis were carried out for source apportionment. • Forest and coal combustion, and vehicular emissions were the major PAH contributors. [ABSTRACT FROM AUTHOR]

Australia has a history of overlooking heavy metal contamination in towns and water bodies that can impact on human and environmental health. Airborne lead pollution in many regional Australian towns is often related to mining, smelting and transport of minerals. Recent studies in Townsville have shown inner city soil and playgrounds, creek and nearby off-shore sediment to have heavy metal concentrations that exceed Australian standards; this contamination is suspected to originate from the port. To assess the port as a current source of lead dust, we evaluated one year of data in 2015-2016 on lead concentration in air from the Department of Environment and Heritage Protection continuous metals monitoring station. The analysis shows that when the wind direction is from the port, and ships are present at the berth where the lead and zinc concentrates are loaded, there is a significant increase in lead concentration. This suggests that shipping activity at the port continues to be the source of lead-laden dust in inner Townsville and in estuarine and coastal marine sediments. The sediments have the highest concentration of lead in Ross Creek, southwest of the port. The geographical relationship between the port, metal analyser and the creek relative to the northeast winds, the latter being directly downwind, suggest that the Ross creek and metal monitoring station have the same source of lead contamination. Our results indicate lead testing in people and wildlife in the area may be warranted to directly assess risks, and that remedial action should continue to focus on reducing escape of lead dust from the port. [ABSTRACT FROM AUTHOR]