51 research outputs found
Salinity variations in the northern Coorong Lagoon, South Australia: Significant changes in the ecosystem following human alteration to the natural water regime
European settlement and drought have significantly impacted the hydrology of the Coorong, a shallow coastal lagoon complex in South Australia, which is part of a terminal wetland at the mouth of the River Murray. An increased salinity associated with lower water levels and progressive isolation from ocean flushes contributed to a severe decline in ecological diversity over the past decades. Here we have conducted a molecular and stable isotopic study of a sedimentary core from the northern Coorong Lagoon spanning more than 5000 years to investigate the recent palaeoenvironmental history of the ecosystem. Major alterations were evident in many biogeochemical parameters in sediments deposited after the 1950s coinciding with the beginning of intensified water regulations. The most prominent shift occurred in ÎŽ13C profiles of C21âC33n-alkanes from average values of â23.5â° to an average of â28.2â°.Further changes included decreases in carbon preference index (CPI) and average chain length (ACL) of the n-alkane series as well as significant increases in algal (e.g. C20 HBI, long chain alkenes and C29-alkadiene) and bacterial (e.g. 13C depleted short chain n-alkanes and hopanoids, ÎŽ13C: â35.9â° to â30.1â°) derived hydrocarbons. Long chain n-alkanes with a strong odd/even predominance as observed here are typically attributed to terrigenous plants. In the Coorong however, terrigenous input to sedimentary OM is only minor. Therefore changes in the before mentioned parameters were attributed to a source transition from a major contribution of macrophytes towards predominantly microalgae and bacteria.ÎŽD values of C21âC33n-alkanes showed a general trend towards more enriched values in younger sediments, indicating an overall rising salinity. However, the most pronounced positive shift in these profiles again occurred after the 1950s. Altogether this study demonstrates that the recent human induced changes of the Coorong hydrology, compounded by a severe drought led to an increase in salinity and alterations of primary production which have been much more significant than natural variations occurring throughout the Holocene over several thousands of years
Hallyu and its effects on the complexities of Asian Australian identity
This thesis analyses the role of Hallyu (Korean popular media) amongst Asian Australian people as they negotiate the tensions between belonging in Australia and connections to their Asian heritage. By looking at how and why participants use and engage with Hallyu 1.0 (Korean television content, âK-dramasâ) and Hallyu 2.0 (Korean Pop Music, âK-popâ), the thesis offers a deep, qualitative study of the mediated experiences of being Asian in Australia. Young diasporic Asian people grow up with a distinct awareness of their cultural differences in Australia. They are often conflicted between feeling obligations to remain connected to their Eastern heritage, whilst trying to find belonging within a Western society. As a global media phenomenon, Hallyu offers symbolic material with which Asian Australians can construct and negotiate their identities. Hallyu (trans. Korean Wave) encompasses a global circulation of Korean media and popular culture which has had an increase in both media and scholarly attention. However, whilst literature goes into great depth on the reasons for its global success, there is a lack of investigation into how Hallyu media as a cultural product is a valuable facilitator for young Asian individuals who are exploring, testing, and understanding their complex identities as being âofâ Australia and simultaneously âotherâ. This thesis contributes to this understanding through semi-structured interviews with nine 1.5 â 3rd generation Asian Australians, aged 18-30 years old, as well as moments of ethnographic observation with selected Hallyu fans. The results show that interviewees feel misunderstood and excluded from White Australian society. In the context of being racialised through their Asianness, participants also discuss a sense of solidarity in being Asian Australian. Hallyu reconnects participants to the Eastern values of their individual cultures, despite being a Korean cultural product. Hallyu provides positive Asian representation and makes being Asian âcoolâ. It also encourages negotiation between Eastern and Western cultures that allows participants to build fluid identities and negotiate the inherent tensions of diaspora. Broadly, this project engages with understandings of dual-identities and how pop culture can influence and contribute to negotiations of identity. Hallyu acts as a heuristic diasporic media for Asian Australians and its consumption and reception provide insights into how young Asian Australians use pop culture to facilitate an understanding of themselves.Thesis (MPhil) -- University of Adelaide, School of Humanities, 202
A diatom-based palaeolimnological investigation of the lower Murray River (south east Australia)
Abstract not availabl
Assessing eutrophication and reference conditions for Scottish freshwater lochs using subfossil diatoms
The definitive version is available at www.blackwell-synergy.com1. The European Council Water Framework Directive requires reference conditions to be determined for all water body types including lakes. We examined the role of palaeolimnology, specifically the diatom record, as a tool for assessing eutrophication and for defining lake reference conditions and ecological status. 2. Sediment cores (representing c.1850 to present day) were taken from 26 Scottish freshwater loch basins. Radiometric dating techniques (210Pb and 137Cs) established a chronology for each core. Two levels of diatom analysis were employed: a relatively high resolution (15â20 samples) at 21 lochs considered of high interest, and a lower resolution (four to five samples) at the remaining sites. 3. Detrended correspondence analysis and dissimilarity measures were applied to the core top (present day) and bottom (reference state, c.1850) samples to assess floristic change at each site. Significant floristic change, indicative of nutrient enrichment, occurred in 18 lochs along a broad trophic gradient. 4. Two-way indicator species analysis (TWINSPAN) was applied to the bottom (c.1850) samples to classify the âreferenceâ diatom assemblages and thereby characterize the reference floras of the different lake types. TWINSPAN identified four site end-groups, each with a characteristic diatom assemblage, although there was some overlap in the taxa present in the four groups. Water depth and productivity were key factors that explained the groupings. 5. Diatom transfer functions that reconstructed total phosphorus (TP) concentrations were used to evaluate eutrophication. Nineteen lochs had increases in diatom-inferred (DI) TP of > 5{micro}g l-1 (five of these > 20{micro}g l-1), six lochs had no change or negligible increases in DI-TP (< 2{micro}g l-1), and there was evidence of a decline in DI-TP in one loch over the period represented by the sediment cores. The inferred increases were significant at 12 lochs. 6. Synthesis and applications . Our data indicate that it may be difficult to find minimally impacted waters to act as reference sites, particularly for shallow, lowland lake types, in the current population. The derivation of site-specific reference conditions from the sediment record is a particularly valuable approach in such cases. Ordination, clustering and dissimilarity measures applied to palaeodata, combined with transfer functions, offer powerful techniques for characterizing lake types, defining ecological and chemical reference conditions, and assessing deviation from the reference state.Helen Bennion, Jennie Fluin and Gavin L. Simpso
Seasonal and interannual variations in diatom assemblages in Murray River connected wetlands in north-west Victoria, Australia
© CSIRO PublishingEpipelic diatom assemblages collected from three wetlands connected to the Murray River displayed considerable variation in response to flooding and drying phases. Murray River water input usually generated diatom assemblages dominated by Aulacoseira species. After isolation, the diatom flora of two wetlands shifted to assemblages of small Fragilariaceae forms. Elevated nutrient levels corresponded with the appearance of eutraphentic taxa such as Cyclotella meneghiniana, Eolimna subminuscula, Luticola mutica and Nitzschia palea. Further evapoconcentration induced shifts to taxa tolerant of elevated salinity levels including Amphora coffeaeformis, Navicula incertata, Staurophora salina and Tryblionella hungarica. Ordination analyses reveal a strong chemical control on the diatom taxa present in the wetlands, in accordance with known ecological preferences for salinity and nutrients. The influence of nitrogen and phosphorus concentrations in controlling diatom assemblages was subordinate to salinity once conductivity values exceeded 1400 ÎŒS cmâ1. The results of such biomonitoring provide a means of interpreting wetland history from fossil assemblages contained in sediment sequences.Peter A. Gell, Ian R. Sluiter and Jennie Flui
Diatom-salinity relationships in wetlands: assessing the influence of salinity variability on the development of inference models
copyright Springer Science+Business Media B.V. 2007Diatoms are among the most widely used indicators of human and climate induced wetland salinity history in the world. This is particularly as a result of the development of diatom-based models for inferring past salinity. These models have primarily been developed from relationships between diatoms and salinity measured at the time of sampling or during the preceding year. Although within site variation in salinity has the potential to reduce the efficacy of such models, its influence has been rarely considered. Hence, diatomâconductivity relationships in eight seasonally monitored wetlands have been investigated. In developing a diatomâconductivity transfer function from these sites, we sought to assess the influence of conductivity variation on diatom inference model performance. Our sites were characterised by variability in conductivity that was not correlated to its range and thus were well suited to an investigation of this type. We found, contrary to expectations, that short-term (seasonal) changes in conductivity which were often dramatic did not result in unduly reduced transfer function performance. By contrast, sites that were more variable in the medium term (5â6 years) tended to have larger model errors. In addition, we identified a secondary ecological gradient in the diatom data which could not be related to any measured variable (including pH, turbidity or nutrient concentrations).John Tibby, Peter A. Gell, Jennie Fluin and Ian R. K. Sluite
Multiproxy palaeoeology reconstruction of the mid-Holocene to present salinity, marine incursions and flow regime of Lake Alexandrina and the Goolwa channel, South Australia.
Multiproxy palaeoecology techniques are used to reconstruct the mid-Holocene to present salinity, marine incursions and flow regime of Lake Alexandrina and the Goolwa channel, South Australia. Microfossils (foraminiferal, ostracoda and diatoms) are analysed in three sediment cores. Foraminiferal remains are used to reconstruct the frequency, duration, and spatial extent of marine incursions upstream through the Goolwa channel to Lake Alexandrina. Diatom analysis provides a quantitative reconstruction of salinity, while the ostracoda analysis is currently exploratory. Three C-14 AMS radiocarbon dates and eight Pb-210 dates for each of the three cores have been submitted for analysis. To support the flow-regime-reconstruction with quantitative data, grain size analysis is included. Preliminary data from the foraminiferal assemblage of core RS1 (taken from just above the Goolwa barrage) illustrates a substantial change in both grain size and presence of foraminifera at a core depth of 130 cm. This may represent a sedimentation rate of 2 cm/yr, since the placement of the Goolwa barrage in 1939. At depths between 130 cm and 0 cm the sediment is barren of foraminifera. Below 130 cm foraminifera are abundant; inner-shelf marine species, especially Elphidium crispum, are dominant from 130 cm to the bottom of the core (216 cm). Only three increments (140-144 cm; 164-168 cm; 174-182 cm) have very low foraminiferal counts (<100). The sediment at these depths is of a much finer grain size. For a majority of the time, it is likely that pre-river-regulation-flow rates of the Murray River were high enough to maintain an open mouth, allowing the mixing of marine and estuarine waters.International Union for Quaternary Researc
Assessing long-term pH change in an Australian river catchment using monitoring and palaeolimnological data
Copyright © 2003 American Chemical SocietyReviews of stream monitoring data suggest that there has been significant acidification (>1.0 pH unit at some sites) of Victorian streamwaters over the past 3 decades. To assess whether these declines are within the range of natural variability, we developed a diatom model for inferring past pH and applied it to a ca. 3500-yr diatom record from a flood plain lake, Callemondah 1 Billabong, on the Goulburn River, which has among the most substantial observed pH declines. The model has a jackkniffed r 2 between diatom inferred and measured pH of 0.77 and a root mean square error of prediction of 0.35 pH units. In the pre-European period, pH was stable (range 6.5-6.7) for approximately 3000 yr. Since European settlement around 160 yr ago, diatom-inferred billabong pH has increased significantly by >0.5 units. We hypothesize that this increase in pH is related to processes associated with land clearance (e.g., increased base cation load and decreased organic acid load). There is no evidence of the recent monitored declines in the Callemondah record, which may indicate that that flood plain lakes and the main stream are experiencing divergent pH trends or that the temporal resolution in the billabong sediment record is insufficient to register recent declines.John Tibby, Michael A. Reid, Jennie Fluin, Barry T. Hart, and A. Peter Kersha
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