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Banks J.L.,University of Melbourne | Ross D.J.,Institute of Marine and Antarctic Studies | Keough M.J.,University of Melbourne | Macleod C.K.,Institute of Marine and Antarctic Studies | And 2 more authors.
Marine Pollution Bulletin | Year: 2013

We investigated the effects of the burrowing cirratulid polychaete Cirriformia filigera (Delle Chiaje, 1828) on benthic respiration and nitrogen regeneration in metal-contaminated estuarine sediments using laboratory mesocosms. C. filigera is a dominant component of assemblages in the most severely contaminated sediments within the Derwent estuary, southern Australia. In the presence of C. filigera sediment O2 consumption doubled, with approximately 55% of this increase due to their respiration and the remaining 45% attributable to oxidation reactions and increased microbial respiration associated with burrow walls. Combined NO3 and NO2 fluxes were unaffected. The addition of labile organic matter did not affect benthic fluxes, in the presence or absence of C. filigera, presumably due to the short timeframe of the experiment and naturally enriched test sediments. The results suggest that a combination of tolerance and burrowing activity enables this species to provide an ecosystem service in the removal of N from contaminated sites. © 2013 Elsevier Ltd.

Banks J.L.,University of Melbourne | Jeff Ross D.,Institute of Marine and Antarctic Studies | Keough M.J.,University of Melbourne | MacLeod C.K.,Institute of Marine and Antarctic Studies | Eyre B.D.,Southern Cross University of Australia
Marine Ecology Progress Series | Year: 2012

Although much work has been done to predict the effects of hypoxia (dissolved oxygen < 2 mg l-1) at regional scales, individual estuaries consist of a patchwork of micro-environments that can have different responses. We followed the effects of extended dissolved oxygen (DO) depletion on benthic fluxes of CO2, O2, NO3 -, NH4 +, N2, PO43 - and Fe from estuarine sediments from 3 shallow sites with different macrofauna communities and levels of organic enrichment. DO depletion was achieved by a prolonged (40 d) dark incubation of sealed sediment cores. There were no discernible differences in NO3 - and N2 fluxes between sites, but the effects of hypoxia on sediment metabolism, and on bioavailable nutrient release, NH4 + and PO 4 3-, were modified by the initial macrofauna communities. The DO in cores containing sediments from a site dominated by small epifauna declined significantly faster than in cores containing a greater portion of burrowing infauna; burrows may provide an oxic reservoir within the sediments. Macrofauna mortality led to a more rapid efflux of mineralization products (CO2, NH4 + and PO4 3-) in the epifaunadominated sites, as the small surface-dwelling animals decomposed more quickly. However, the cores were sealed, preventing migration of mobile epifauna away from the hypoxic conditions. The site with the lowest abundance of macrofauna also contained a large amount of refractory organic matter. Decomposition of this material was slow, with little release of nutrients. The study highlights the fact that environmental patchiness can modify the effects of hypoxia and stresses the importance of deeper burrowing fauna as a buffer against declining DO conditions. © 2012 Inter-Research.

Banks J.L.,University of Melbourne | Ross D.J.,Institute of Marine and Antarctic Studies | Keough M.J.,University of Melbourne | Eyre B.D.,Southern Cross University of Australia | Macleod C.K.,Institute of Marine and Antarctic Studies
Science of the Total Environment | Year: 2012

Nutrient inputs to estuarine and coastal waters worldwide are increasing and this in turn is increasing the prevalence of eutrophication and hypoxic and anoxic episodes in these systems. Many urbanised estuaries are also subject to high levels of anthropogenic metal contamination. Environmental O2 levels may influence whether sediments act as sinks or sources of metals. In this study we investigated the effect of an extended O2 depletion event (40days) on fluxes of trace metals (and the metalloid As) across the sediment-water interface in sediments from a highly metal contaminated estuary in S.E. Tasmania, Australia. We collected sediments from three sites that spanned a range of contamination and measured total metal concentration in the overlying water using sealed core incubations. Manganese and iron, which are known to regulate the release of other divalent cations from sub-oxic sediments, were released from sediments at all sites as hypoxia developed. In contrast, the release of arsenic, cadmium, copper and zinc was comparatively low, most likely due to inherent stability of these elements within the sediments, perhaps as a result of their refractory origin, their association with fine-grained sediments or their being bound in stable sulphide complexes. Metal release was not sustained due to the powerful effect of metal-sulphide precipitation of dissolved metals back into sediments. The limited mobilisation of sediment bound metals during hypoxia is encouraging, nevertheless the results highlight particular problems for management in areas where hypoxia might occur, such as the release of metals exacerbating already high loads or resulting in localised toxicity. © 2012 Elsevier B.V.

News Article | August 24, 2016
Site: www.rdmag.com

Elephant seals have helped scientists to demonstrate that fresh water from Antarctic’s melting ice shelves slows the processes responsible for the formation of deep-water ocean currents that regulate global temperatures. The study, led by Dr Guy Williams from the Institute of Marine and Antarctic Studies and Antarctic Climate and Ecosystems CRC, is published today in Nature Communications. Macquarie’s Professor Rob Harcourt from the Department of Biological Sciences is the Facility Leader for the elephant seal IMOS Animal Tracking program through which the data is collected. Dr Williams said the findings raised questions about potential future changes in global ocean circulation patterns. “Antarctica and the Southern Ocean are like a beating heart, producing deep and powerful currents of cold water that drive global ocean mixing and regulate atmospheric temperatures,” Dr Williams said. “These currents begin with intense sea ice formation around the Antarctic continent in winter, which creates cold, salty and dense water that sinks and flows away from the continent in large volumes. “If this production of Antarctic bottom water weakens, it leads to changes in global ocean circulation patterns that can, in turn, lead to changes in the global climate.” In 2011, the same team of researchers discovered a fourth source of Antarctic Bottom Water off Cape Darnley in East Antarctica. The latest research published today, including an additional two years of data, shows that Prydz Bay makes an important secondary contribution to Cape Darnley Bottom Water. “However we found that the contribution from Prydz Bay is less salty and dense due to the influence of nearby ice shelves,” Dr Williams said. “We can easily imagine that the production of these global ocean currents will slow as the rate of ice shelf melting all around Antarctica continues to increase.” Since 2011, elephant seals at Davis Station have been instrumented with oceanographic sensors as part of Australia’s Integrated Marine Observing System (IMOS) , supported by Australian Government.  The seal tagging component of IMOS is supported through logistical support and funding from the Australian Government’s Australian Antarctic Program. When the seals surface, their sensors relay information back to land via satellite, and the near real-time data is made available via the Global Telecommunication System of the World Meteorological Organization for immediate use. IMOS also makes the data available via their data portal. The oceanographic data collected by the seals is also used for ecological research into their behaviour and aids in conservation.

Simon K.J.,Australian Nuclear Science and Technology Organisation | Pedro J.B.,Institute of Marine and Antarctic Studies | Pedro J.B.,Australian Antarctic Division | Smith A.M.,Australian Nuclear Science and Technology Organisation | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2013

10Be accelerator mass spectrometry (AMS) is an increasingly important tool in studies ranging from exposure age dating and palaeo-geomagnetism to the impact of solar variability on the Earth's climate. High levels of boron in BeO AMS targets can adversely impact the quality of 10Be measurements through interference from the isobar 10B. Numerous methods in chemical sample preparation and AMS measurement have been employed in order to reduce the impact of excessive boron rates. We present details of a method developed to chemically reprocess a set of forty boron-contaminated BeO targets derived from modern Antarctic ice. Previously, the excessive boron levels in these samples, as measured in an argon-filled absorber cell preceding the ionisation detector, had precluded routine AMS measurement. The procedure involved removing the BeO + Nb mixture from the target holders and dissolving the BeO in hot concentrated H 2SO4. The solution was then heated with HF to remove the boron as volatile BF3 before re-precipitating as Be(OH)2 and calcining to BeO. This was again mixed with niobium and pressed into fresh target holders. Following reprocessing, the samples gave boron rates reduced by 10-100×, which were sufficiently low and similar to previous successful batches of ice core, snow and associated blank samples, thus allowing a successful 10Be measurement in the absence of any boron correction. Overall recovery of the BeO for this process averaged 40%. Extensive testing of relevant processing equipment and reagents failed to determine the source of the boron. As a precautionary measure, a similar H2SO4 + HF step has been subsequently added to the standard ice processing method. © 2012 Elsevier B.V. All rights reserved.

Currey L.M.,James Cook University | Williams A.J.,James Cook University | Williams A.J.,British Petroleum | Mapstone B.D.,CSIRO | And 10 more authors.
Journal of Fish Biology | Year: 2013

Life-history characteristics of six tropical Lethrinus species sampled from the Great Barrier Reef World Heritage Area were compared. Two species groups were identified based on fork length (LF): large species with maximum LF > 640 mm (longface emperor Lethrinus olivaceus, yellowlip emperor Lethrinus xanthochilus and spangled emperor Lethrinus nebulosus) and small species with maximum LF < 480 mm (Pacific yellowtail emperor Lethrinus atkinsoni, pink ear emperor Lethrinus lentjan and ornate emperor Lethrinus ornatus). Lifespan was not correlated with LF. Early growth for all species was rapid and similar during the first few years of life, but coefficients of the von Bertalanffy growth function varied considerably among species. Growth also differed between sexes for L. atkinsoni. Reproductive characteristics varied among species, with peak periods of spawning occurring in November to December for L. atkinsoni, July to August for L. nebulous, September to October for L. olivaceus and a protracted season for L. lentjan, although fewer samples were available for the last two species. Sex-specific LF and age distributions and gonad histology of L. lentjan were suggestive of a functional protogynous reproductive pattern, as observed in other lethrinids. Gonad histology indicated non-functional protogynous hermaphroditism for L. atkinsoni and L. nebulosus. The diversity of life histories among these closely related species emphasizes the difficulty in devising single management strategies appropriate for multi-species fisheries and illustrates the importance of understanding species-specific life histories to infer responses to exploitation. Journal of Fish Biology. © 2013 The Fisheries Society of the British Isles.

Abrantes K.G.,Catholic University of Leuven | Abrantes K.G.,James Cook University | Barnett A.,Deakin University | Barnett A.,Institute of Marine and Antarctic Studies | And 2 more authors.
Ecosphere | Year: 2013

Little is known on the degree to which terrestrial organic matter delivered to tropical estuaries contributes to estuarine consumers. Here, stable isotope analysis is used to constrain this contribution for contrasting east African estuaries whose catchments differ in relative C3/C4 vegetation cover. As these two types of vegetation differ strongly in d13C, we anticipated that terrestrial subsidies would be reflected in a gradient in estuarine consumer d13C values, following the relative importance of C3 (characterised by low d13C) vs. C4 (characterised by high d13C) cover. Five estuaries were sampled for aquatic biogeochemical parameters, primary producers and consumers of different trophic ecologies: the Zambezi (catchment with a C3/C4 cover of 61/39%) in Mozambique, the Tana in Kenya (36/64%) and the Betsiboka (42/58%), Rianila (85/15%) and Canal des Pangalanes (C3-dominated) in Madagascar. Sampling was done before and after the 2010/2011 wet season. There were positive relationships between the proportion of C4 cover in the catchment and turbidity, d13CDIC, d13CDOC, d13CPOC and d15NPN. There were also significant positive relationships between d13CPOC and consumer d13C and between d15NPN and consumer d15N for all consumer trophic guilds, confirming the incorporation of organic material transported from the catchments by estuarine consumers, and implying that this material is transported up to high trophic level fish. Bayesian mixing models confirmed that C4 material was the most important source for the highly turbid, C4-dominated estuaries, contributing up to 61-91% (95% CI) to phytodetritivorous fish in the Betsiboka, whereas for the less turbid C3-dominated estuaries terrestrial subsidies were not as important and consumers relied on a combination of terrestrial and aquatic sources. This shows that the ecology of the overall catchment affects the estuaries at the most basic, energetic level, and activities that alter the turbidity and productivity of rivers and estuaries can affect food webs well beyond the area of impact. © 2013 Abrantes et al.

Abrantes K.G.,Catholic University of Leuven | Abrantes K.G.,James Cook University | Barnett A.,Deakin University | Barnett A.,Institute of Marine and Antarctic Studies | Bouillon S.,Catholic University of Leuven
Functional Ecology | Year: 2014

Quantitative tools to describe biological communities are important for conservation and ecological management. The analysis of trophic structure can be used to quantitatively describe communities. Stable isotope analysis is useful to describe trophic organization, but statistical models that allow the identification of general patterns and comparisons between systems/sampling periods have only recently been developed. Here, stable isotope-based Bayesian community-wide metrics are used to investigate patterns in trophic structure in five estuaries that differ in size, sediment yield and catchment vegetation cover (C3/C4): the Zambezi in Mozambique, the Tana in Kenya and the Rianila, the Betsiboka and Pangalanes Canal (sampled at Ambila) in Madagascar. Primary producers, invertebrates and fish of different trophic ecologies were sampled at each estuary before and after the 2010-2011 wet season. Trophic length, estimated based on δ15N, varied between 3·6 (Ambila) and 4·7 levels (Zambezi) and did not vary seasonally for any estuary. Trophic structure differed the most at Ambila, where trophic diversity and trophic redundancy were lower than at the other estuaries. Among the four open estuaries, the Betsiboka and Tana (C4-dominated) had lower trophic diversity than the Zambezi and Rianila (C3-dominated), probably due to the high loads of suspended sediment, which limited the availability of aquatic sources. There was seasonality in trophic structure at Ambila and Betsiboka, as trophic diversity increased and trophic redundancy decreased from the prewet to the postwet season. For Ambila, this probably resulted from the higher variability and availability of sources after the wet season, which allowed diets to diversify. For the Betsiboka, where aquatic productivity is low, this was likely due to a greater input of terrestrial material during the wet season. The comparative analysis of community-wide metrics was useful to detect patterns in trophic structure and identify differences/similarities in trophic organization related to environmental conditions. However, more widespread application of these approaches across different faunal communities in contrasting ecosystems is required to allow identification of robust large-scale patterns in trophic structure. The approach used here may also find application in comparing food web organization before and after impacts or monitoring ecological recovery after rehabilitation. © 2013 The Authors. Functional Ecology © 2013 British Ecological Society.

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