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  • This dataset maps the geomorphic habitat environments (facies) for 63 Northern Territory coastal waterways. This version of the dataset includes 48 newly mapped estuaries, classified as 'Near pristine'. The classification system contains 12 easily identifiable and representative environments: Barrier/back-barrier, Bedrock, Central Basin, Channel, Flood- and Ebb-tide Delta, Fluvial (bay-head) Delta, Intertidal Flats, Mangrove, Rocky Reef, Saltmarsh/Saltflat, Tidal Sand Banks (and Unassigned). These types represent habitats found across all coastal systems in Australia. Estuaries on the northern Arnhem Land, Gulf of Carpentaria coasts are predominantly tide-dominated estuaries, which vary greatly in size and floodplain characteristics.

  • This dataset maps the geomorphic habitat environments (facies) for 103 Western Australia coastal waterways. The classification system contains 11 easily identifiable and representative environments: Barrier/back-barrier, Central basin, Channel, Coral, Flood- and Ebb-tide Delta, Fluvial (bay-head) Delta, Intertidal Flats, Mangrove, Rocky Reef, Saltmarsh/Saltflat, Tidal Sand Banks (and Unassigned). These types represent habitats found across all coastal systems in Australia. Western Australia has a diverse range of Estuaries due to different climates. Ranging from mostly "near pristine" and tide influenced estuaries in the north to "near pristine" wave dominated estuaries in the southwest region.

  • This dataset maps the geomorphic habitat environments (facies) for 54 Victorian coastal waterways. The classification system contains 11 easily identifiable and representative environments: Barrier/back-barrier, Central Basin, Channel, Coral, Flood- and Ebb-tide Delta, Fluvial (bay-head) Delta, Intertidal Flats, Mangrove, Rocky Reef, Saltmarsh/Saltflat, Tidal Sand Banks (and Unassigned). These types represent habitats found across all coastal systems in Australia. Most of the 54 coastal waterways have a "Modified" environmental condition (as opposed to "Near Pristine"), according to the National Land and Water Resources Audit definition.

  • Moreton Bay (MB) is a large (~1800 square km), stressed (with recent outbreaks of the cyanobacteria Lyngbia majscula), sub-tropical estuary which receives urban and rural runoff from a large catchment. Silicon is an essential nutrient for diatomaceous phytoplankton growth in coastal ecosystems. BSi (biogenic silicon) in surface sediments, pore water DSi (dissolved silicate, SiO4--) and benthic DSi fluxes were used as tracers of the formation and degradation of organic matter (OM) in MB. This work has implications for N & P cycling, water quality and eutrophication. BSi, TOC (both up to 2 wt%), TN & TP and diatom sterol biomarkers were all highest in the muddy sediments of western MB that is ~65% of the bay's area. We found that diatoms dominated OM cycling in western MB, and the benthic DSi flux accounted for ~80% of the pelagic productivity. Our conceptual model is that diatoms being heavy (because of their Si content) sink rapidly to the sediments where their biomass-N (OM-N) was denitrified to N2 and lost to the atmosphere with an efficiency of about 50%. Approximately 60% of OM-P, subsequent to degradation, remained trapped within the sediment. Diatoms therefore are an important vector to repeatedly deliver river-borne N & P to their respective sinks. However, diatomaceous OM contributed only about 20% of the OM input to the marine sands of eastern MB, about 34% of the bay's area. The principal OM input to the sandy sediments was attributed to benthic photosynthesis and N-fixation with rates of N-fixation (estimated from pore water DIN gradients) at 1.5 - 3.5 mmol m-2d-1. OM was rapidly and efficiently degraded (principally by O2), with little net accumulation and burial in sediments. N was denitrified efficiently (~100%). DIP must have been recycled rapidly in the top few cm's of the sandy sediments to support N-fixation. A whole-bay silicate budget indicated that: 1. DSi fluxes through the western margin of MB were about 4- fold those in eastern MB. 2. Pelagic diatom productivity was supported (approximately) by the benthic fluxes of DSi. 3. The DSi inventory was recycled through diatomaceous phytoplankton in about 15 days. 4. The export of DSi to the sea was about the same as the combined terrestrial and small marine inputs.

  • An investigation of beach-sand heavy-mineral deposits between the mouth of the Clarence River in northern New South Wales, and North Stradbroke Island in southern Queensland, was made by the Bureau of Mineral Resources during the years 1948 to 1950. The work done between the mouth of the Clarence River and Southport comprised detailed boring and sampling of beaches and coastal dunes and portion of coastal plains up to a mile or two inland. The levels of the bore-collars were determined in relation to high water mark on the beaches. On North Stradbroke Island, boring was done by Zinc Corporation and a reconnaissance geological investigation by the Bureau of Mineral Resources. The results of this work are being published by the Bureau, and portions of it which have a bearing on the changing sea-levels are summarized below.

  • Benthic nutrient fluxes from the sediments were measured at three Sites in the Bombah Broadwater of Myall Lakes during the winter (June) of 2000. Surface sediments (0-1 cm) and two cores were collected at each site and processed for measurements of carbon and nitrogen isotopic composition of the OM (organic matter), biomarkers and bulk sediment composition (OM and major cations). Pore waters were extracted from sediments and measured for both organic and inorganic metabolites. Biomarker, benthic flux data and the compositions of inorganic metabolites in pore waters indicated that Redfield OM (organic matter) was predominant in the sediments and mostly diatomaceous and probably responsible for the observed release of nutrients from the sediments to t he overlying waters. Carbon degradation rates in the sediments, during these winter month, varied between 5-47 mmol m-2 d-1 (60-564 µg m-2d-1) and were highest in the muddy sediments (mean = 21.3 +/-12.7 mmol m-2 d-1) as compared to the sandy sediments (mean = 11.6 +/-4.8 mmol m-2 d-1). DIN fluxes were less than those predicted from CO2 fluxes and Redfield stoichiometry and the `missing nitrogen' (subsequently determined by mass spectrometry as N2) was indicative of denitrification in the surface sediments. Rates of denitrification calculated from N2 directly and from `missing N' were similar and up to 5.1 mmol N m-2 d-1. There was no evidence of organic metabolite fluxes although the organic and inorganic metabolite concentrations were similar in the pore waters. Denitrification efficiencies were high (mean = 80 +/- 4%) in the sandy sediments and lower (although there was considerable variability) in the muddy sediments (mean =38% +/- 9%). Most DIP (generally > 70%) liberated to pore waters during OM degradation was not released into overlying waters but remained trapped and enriched in surface sediments. Benthic nutrient fluxes (average DIN/DIP = 131) were preferentially enriched in N compared to the OM (N/P = 16) raining into the sediments. Adjective biophysical processes (not diffusive) dominated the fluxes of metabolites across the sediment -water interface.

  • Permeable, sandy sediments cover most of the continental shelf. The important role of pore-water advective flow on biogeochemical processes in these sediments has been highlighted in recent studies. Such flow can be driven by wave-action, water-density and interactions between topography and bottom currents, in addition to biological activity, and can create spatially complex and highly dynamic benthic environments in which processes vary on timescales ranging from minutes to months. It is well known that the patchiness of soft sediment (organic matter/bacteria, particle diversity, redox) is likely to be a major determinant of species diversity, but previous studies have not specifically defined patches based on a range of biologically-relevant physico-chemical variables, nor observed how patches change across time. This study, as part of the Surrogates Program in the Commonwealth Environmental Research Facilities Marine Biodiversity Hub, investigated temporal changes in the geochemistry, physical sediments and infauna of sandy sediments in Jervis Bay at two times.

  • We examine surface sediment and water column total nutrient and chlorophyll a concentrations for 12 estuaries with average water depths <4 m, and calculated sediment loads ranging from 0.2 to 10.8 kg m-2 year-1. Sediment total nitrogen, phosphorus and organic carbon concentrations vary inversely with sediment loads due to: (i) the influx of more mineral-rich sediment into the estuaries; and (ii) increasing sediment sulfidation. Sediment total organic carbon (TOC) : total sulfur (TS) and TS : Fe(II) ratios correlated to sediment loads because enhanced sedimentation increases burial, hence the importance of sulfate reduction in organic matter degradation. Curvilinear relationships were found between a weathering index and organic matter 13C in sediment, and sediment load. The rising phase of the curve (increasing weathering, lighter isotopic values) at low to intermediate loads relates to soil erosion, whereas regolith or bedrock erosion probably explains the declining phase of the curve (decreasing weathering, heavier isotopic values) at higher sediment loads. The pattern of change for water column total nutrients (nitrogen and phosphorus) with sediment loads is similar to that of the weathering index. Most water quality problems occur in association with soil erosion, and at sediment loads that are intermediate for the estuaries studied. Limited evidence is presented that flushing can moderate the impact of sediment loads upon the estuaries.

  • A sequence of stranded coastal barriers in south-east South Australia preserves a record of sea-level variations over the past 800 ka. Huntley et al. (Quat. Sci. Rev. 12 (1993a) 1; Quat. Sci. Rev. 13 (1994a) 201) attempted to test thermoluminescence (TL) dating methods and found good agreement between quartz TL ages with independent ages for these dunes. We investigate the accuracy of the single-aliquot regenerative-dose (SAR) procedure (Radiat. Meas. 32 (2000) 57) over an extended age range of 0-250 ka, by comparing SAR-OSL ages determined on quartz extracts from these dunes with the existing chronology. We show that Robe II range is 60 ka, and that Robe III is 100 ka old. Not surprisingly, the OSL ages increase monotonically from the Robe II range to the West Naracoorte range. For the younger dunes (<240 ka), the SAR-OSL ages agree with the expected ages within 1 errors, whereas for the older dunes the SAR ages are consistent with independent ages within 2 error limits. We consider these results to be very promising, and lend support to the large number of quartz SAR-OSL ages being presented in the literature, where such comparisons with independent chronology are not usually possible.