- Barr, Cameron, Tibby, John, Gell, Peter, Tyler, Jonathan, Zawadzki, Atun, Jacobsen, Geraldine
- Authors: Barr, Cameron , Tibby, John , Gell, Peter , Tyler, Jonathan , Zawadzki, Atun , Jacobsen, Geraldine
- Date: 2014
- Type: Text , Journal article
- Relation: Quaternary Science Reviews Vol. 95, no. (July 2014 2014), p. 115-131
- Full Text: false
- Reviewed:
- Description: Climates of the last two millennia have been the focus of numerous studies due to the availability of high-resolution palaeoclimate records and the occurrence of divergent periods of climate, commonly referred to as the 'Medieval Climatic Anomaly' and 'The Little Ice Age'. The majority of these studies are centred in the Northern Hemisphere and, in comparison, the Southern Hemisphere is relatively under-studied. In Australia, there are few high-resolution, palaeoclimate studies spanning a millennium or more and, consequently, knowledge of long-term natural climate variability is limited for much of the continent. South-eastern Australia, which recently experienced a severe, decade-long drought, is one such region.Results are presented of investigations from two crater lakes in the south-east of mainland Australia. Fluctuations in lake-water conductivity, a proxy for effective moisture, are reconstructed at sub-decadal resolution over the past 1500 years using a statistically robust, diatom-conductivity transfer function. These data are interpreted in conjunction with diatom autecology. The records display coherent patterns of change at centennial scale, signifying that both lakes responded to regional-scale climate forcing, though the nature of that response varied between sites due to differing lake morphometry. Both sites provide evidence for a multi-decadal drought, commencing ca 650 AD, and a period of variable climate between ca 850 and 1400 AD. From ca 1400-1880 AD, coincident with the timing of the 'Little Ice Age', climates of the region are characterised by high effective moisture and a marked reduction in inter-decadal variability. The records provide context for climates of the historical period and reveal the potential for more extreme droughts and more variable climate than that experienced since European settlement of the region ca 170 years ago.
Resilience in a aquatic ecosystems : Developing predictive models to explain the effects of anthropogenic stressors on Murray-Darling Basin billabongs
- Reid, Michael, Gell, Peter, Davidson, Thomas, Sayer, Carl, Tibby, John, Fluin, Jennie
- Authors: Reid, Michael , Gell, Peter , Davidson, Thomas , Sayer, Carl , Tibby, John , Fluin, Jennie
- Date: 2014
- Type: Text , Conference paper
- Relation: Symposium on Australia-China Wetland Network Research Partnership; Nanjing Institute of Geography and Limnology Chinese Academy of Sciences (NIGLAS) Nanjing, China; 23rd-28th December 2014 p. 61-67
- Full Text:
- Reviewed:
- Description: Freshwater ecosystems are among the most threatened in the world (MEA 2005) and have been identified as one of the ten Australian ecosystems most vulnerable to tipping points. The floodplain lakes and wetlands (billabongs) of the Murray-Darling Basin (MDB) are hotspots of productivity and diversity and provide important breeding, feeding and refuge habitat for a range of floodplain river biota, as well as important ecosystem goods and services by way of flood mitigation, nutrient cycling and sediment trapping. Nonetheless, MDB billabongs are threatened by water resource and agricultural development and climate change. In recognition of these threats, water dependent ecosystems of the MDB are currently subject to expensive and controversial management measures involving water buy backs estimated to cost up to $30 billion and the subsequent delivery of environmental water. The need to understand the critical drivers of change and the internal system interactions that underlie ecosystem responses in floodplain river ecosystems has never been greater. This project will develop ecosystem response models that will not only identify the critical threatening drivers, but also provide the guidance necessary to rehabilitate these important ecosystems.
- Authors: Reid, Michael , Gell, Peter , Davidson, Thomas , Sayer, Carl , Tibby, John , Fluin, Jennie
- Date: 2014
- Type: Text , Conference paper
- Relation: Symposium on Australia-China Wetland Network Research Partnership; Nanjing Institute of Geography and Limnology Chinese Academy of Sciences (NIGLAS) Nanjing, China; 23rd-28th December 2014 p. 61-67
- Full Text:
- Reviewed:
- Description: Freshwater ecosystems are among the most threatened in the world (MEA 2005) and have been identified as one of the ten Australian ecosystems most vulnerable to tipping points. The floodplain lakes and wetlands (billabongs) of the Murray-Darling Basin (MDB) are hotspots of productivity and diversity and provide important breeding, feeding and refuge habitat for a range of floodplain river biota, as well as important ecosystem goods and services by way of flood mitigation, nutrient cycling and sediment trapping. Nonetheless, MDB billabongs are threatened by water resource and agricultural development and climate change. In recognition of these threats, water dependent ecosystems of the MDB are currently subject to expensive and controversial management measures involving water buy backs estimated to cost up to $30 billion and the subsequent delivery of environmental water. The need to understand the critical drivers of change and the internal system interactions that underlie ecosystem responses in floodplain river ecosystems has never been greater. This project will develop ecosystem response models that will not only identify the critical threatening drivers, but also provide the guidance necessary to rehabilitate these important ecosystems.
- Mills, Keely, Gell, Peter, Gergis, Joelle, Baker, Patrick J., Finlayson, C. Max, Hesse, Paul, Jones, R., Kershaw, Peter, Pearson, Stuart, Treble, Pauline, Barr, Cameron, Brookhouse, Matthew, Drysdale, Russell, McDonald, Janece, Haberle, Simon, Reid, Michael, Thoms, M., Tibby, John
- Authors: Mills, Keely , Gell, Peter , Gergis, Joelle , Baker, Patrick J. , Finlayson, C. Max , Hesse, Paul , Jones, R. , Kershaw, Peter , Pearson, Stuart , Treble, Pauline , Barr, Cameron , Brookhouse, Matthew , Drysdale, Russell , McDonald, Janece , Haberle, Simon , Reid, Michael , Thoms, M. , Tibby, John
- Date: 2013
- Type: Text , Journal article
- Relation: Australian Journal of Earth Sciences Vol. 60, no. 5 (2013), p. 561-571
- Full Text: false
- Reviewed:
- Description: The management of the water resources of the Murray-Darling Basin (MDB) has long been contested, and the effects of the recent Millennium drought and subsequent flooding events have generated acute contests over the appropriate allocation of water supplies to agricultural, domestic and environmental uses. This water-availability crisis has driven demand for improved knowledge of climate change trends, cycles of variability, the range of historical climates experienced by natural systems and the ecological health of the system relative to a past benchmark. A considerable volume of research on the past climates of southeastern Australia has been produced over recent decades, but much of this work has focused on longer geological time-scales, and is of low temporal resolution. Less evidence has been generated of recent climate change at the level of resolution that accesses the cycles of change relevant to management. Intra-decadal and near-annual resolution (high-resolution) records do exist and provide evidence of climate change and variability, and of human impact on systems, relevant to natural-resource management. There exist now many research groups using a range of proxy indicators of climate that will rapidly escalate our knowledge of management-relevant, climate change and variability. This review assembles available climate and catchment change research within, and in the vicinity of, the MDB and portrays the research activities that are responding to the knowledge need. It also discusses how paleoclimate scientists may better integrate their pursuits into the resource-management realm to enhance the utility of the science, the effectiveness of the management measures and the outcomes for the end users.
- Description: C1
A history of aquatic plants in the Coorong, a Ramsar-listed coastal wetland, South Australia
- Dick, J., Haynes, Deborah, Tibby, John, Garcia, Adriana, Gell, Peter
- Authors: Dick, J. , Haynes, Deborah , Tibby, John , Garcia, Adriana , Gell, Peter
- Date: 2011
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. 46, no. 4 (2011), p. 623-635
- Full Text: false
- Reviewed:
- Description: The Coorong in South Australia is an internationally recognised ecologically significant coastal lagoon that extends 140 km south-east from the mouth of the River Murray. The Coorong has increasingly been impacted by a variety of human activities. Declining migratory bird abundance has been linked to the loss of Ruppia tuberosa, an aquatic plant that is the main feedstock for a wide variety of water birds. Analysis of Ruppia remains from a radiometrically dated core in the southern lagoon of The Coorong shows that the salt-tolerant annual Ruppia tuberosa has only been present at this site in recent times. By contrast, the perennial Ruppia megacarpa, which has limited tolerance to elevated salinity, appears to have been present at the site for several millennia, although it had never been observed in ecological surveys of this part of The Coorong. Diatom analysis from the same core reveals a shift from estuarine/marine assemblages to an assemblage reflective of elevated salinity levels. Charophyte, ostracod and foraminifera remains also indicate that the change in the aquatic plant community is associated with increased salinity at the study site since European settlement. Elevated salinity is the result of catchment modifications which have reduced freshwater inflows at the northern and southern extremities of The Coorong, and marine input via the Murray Mouth. This study demonstrates the utility of multiproxy palaeoecological data in addressing complex management questions. In the absence of such information, managers must ultimately rely on data sourced only from the historical record which, more often than not, is already skewed by the impact of European settlement. © 2011 Springer Science+Business Media B.V.
Influence of River Murray water on River Torrens' water quality
- Tibby, John, Cox, Asta, Gell, Peter
- Authors: Tibby, John , Cox, Asta , Gell, Peter
- Date: 2010
- Type: Text , Book chapter
- Relation: Adelaide: Water of a city p.
- Full Text: false
- Reviewed:
- Description: "Transfers of River Murray water to the River Torrens commenced in 1955. This box focuses on the water quality impacts of this transfer on River Torrens storages."
Anthropogenic acceleration of sediment accretion in lowland floodplain wetlands, Murray-Darling Basin, Australia
- Gell, Peter, Fluin, J., Tibby, John, Hancock, Gary, Harrison, Jennifer, Zawadzki, Atun, Haynes, Deborah, Khanum, Syeda, Little, Fiona, Walsh, Brendan
- Authors: Gell, Peter , Fluin, J. , Tibby, John , Hancock, Gary , Harrison, Jennifer , Zawadzki, Atun , Haynes, Deborah , Khanum, Syeda , Little, Fiona , Walsh, Brendan
- Date: 2009
- Type: Text , Journal article
- Relation: Geomorphology Vol. 108, no. 1-2 (2009), p. 122-126
- Full Text:
- Reviewed:
- Description: Over the last decade there has been a deliberate focus on the application of paleolimnological research to address issues of sediment flux and water quality change in the wetlands of the Murray-Darling Basin of Australia. This paper reports on the research outcomes on cores collected from sixteen wetlands along the Murrumbidgee-Murray River continuum. In all sixteen wetlands radiometric techniques and exotic pollen biomarkers were used to establish sedimentation rates from the collected cores. Fossil diatom assemblages were used to identify water source and quality changes to the wetlands. The sedimentation rates of all wetlands accelerated after European settlement, as little as two-fold, and as much as eighty times the mean rate through the Late Holocene. Some wetlands completely infilled through the Holocene, while others have rapidly progressed towards a terrestrial state due to accelerated accretion rates. Increasing wetland salinity and turbidity commenced within decades of settlement, contributing to sediment inputs. The sedimentation rate was observed to slow after river regulation in one wetland, but has accelerated recently in others. The complex history of flooding and drying, and wetland salinisation and eutrophication, influence the reliability of models used to establish recent, fine-resolution chronologies with confidence and the capacity to attribute causes to documented effects. © 2008 Elsevier B.V.
- Description: 2003006710
- Authors: Gell, Peter , Fluin, J. , Tibby, John , Hancock, Gary , Harrison, Jennifer , Zawadzki, Atun , Haynes, Deborah , Khanum, Syeda , Little, Fiona , Walsh, Brendan
- Date: 2009
- Type: Text , Journal article
- Relation: Geomorphology Vol. 108, no. 1-2 (2009), p. 122-126
- Full Text:
- Reviewed:
- Description: Over the last decade there has been a deliberate focus on the application of paleolimnological research to address issues of sediment flux and water quality change in the wetlands of the Murray-Darling Basin of Australia. This paper reports on the research outcomes on cores collected from sixteen wetlands along the Murrumbidgee-Murray River continuum. In all sixteen wetlands radiometric techniques and exotic pollen biomarkers were used to establish sedimentation rates from the collected cores. Fossil diatom assemblages were used to identify water source and quality changes to the wetlands. The sedimentation rates of all wetlands accelerated after European settlement, as little as two-fold, and as much as eighty times the mean rate through the Late Holocene. Some wetlands completely infilled through the Holocene, while others have rapidly progressed towards a terrestrial state due to accelerated accretion rates. Increasing wetland salinity and turbidity commenced within decades of settlement, contributing to sediment inputs. The sedimentation rate was observed to slow after river regulation in one wetland, but has accelerated recently in others. The complex history of flooding and drying, and wetland salinisation and eutrophication, influence the reliability of models used to establish recent, fine-resolution chronologies with confidence and the capacity to attribute causes to documented effects. © 2008 Elsevier B.V.
- Description: 2003006710
Complex reservoir sedimentation revealed by an unusual combination of sediment records, Kangaroo Creek Reservoir, South Australia
- Tibby, John, Gell, Peter, Hancock, Gary, Clark, M.
- Authors: Tibby, John , Gell, Peter , Hancock, Gary , Clark, M.
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. , no. (2009), p. 1-15
- Full Text:
- Reviewed:
- Description: Despite their direct links to human use, reservoirs are not widely utilised, relative to natural lakes, for deriving sediment histories. One explanation is the complex sedimentation patterns observed in water storages. Here a highly unusual combination of sedimentary records is used to determine the sedimentation history of Kangaroo Creek Reservoir, South Australia. We compare contiguous high resolution (0.5 cm sampling interval) diatom records from an almost 1.3 m core extracted from the bottom of the reservoir and from a 0.4 m monolith of sediment perched 15 m above the reservoir bottom on a disused bridge that was submerged following initial reservoir filling in 1970. The diatom histories are supplemented by evidence provided by other indicators, most notably radionuclide concentrations and ratios. Interestingly, despite the fact that the reservoir has been >20 m deep for more than 70% of its recorded history, distinct sections of the reservoir bottom core, but not the bridge monolith, are dominated by non-planktonic diatoms. We attribute the occurrences of these phases to inflows that occur following heavy catchment rains at times when the reservoir is drawn down. These characteristic sections have, in turn, been used to refine the site's chronology. Despite having a length of almost 1.3 m, a variety of data suggests that the core has not recovered pre-reservoir sediment, but rather spans the period from 1981 (11 years after first filling) to 2001, when the core was extracted. It is clear, therefore, that sediments in the bottom of the reservoir are accumulating rapidly (>7 cm year-1), although more than 40% of this deposition occurs in less than 5% of the time. It appears that in the period 1996-2001, quiescent sedimentation rates, both in the perched bridge locality and on the reservoir bottom, slowed in response to reduced stream flow. Our findings indicate that, with caution, complex patterns of sedimentation in water storages can be disentangled. However, it was difficult to precisely correlate diatom sequences from the two records even in periods of quiescent sedimentation, suggesting that reservoir bottom diatom sequences should be interpreted with considerable caution. Furthermore, while storm-derived inflows such as those identified may deliver a substantial proportion of sediment and phosphorus load to storages, the ensuing deposition patterns may render much of the phosphorus unavailable to the overlying waters. © 2009 Springer Science+Business Media B.V.
- Description: Despite their direct links to human use, reservoirs are not widely utilised, relative to natural lakes, for deriving sediment histories. One explanation is the complex sedimentation patterns observed in water storages. Here a highly unusual combination of sedimentary records is used to determine the sedimentation history of Kangaroo Creek Reservoir, South Australia. We compare contiguous high resolution (0.5 cm sampling interval) diatom records from an almost 1.3 m core extracted from the bottom of the reservoir and from a 0.4 m monolith of sediment perched 15 m above the reservoir bottom on a disused bridge that was submerged following initial reservoir filling in 1970. The diatom histories are supplemented by evidence provided by other indicators, most notably radionuclide concentrations and ratios. Interestingly, despite the fact that the reservoir has been >20 m deep for more than 70% of its recorded history, distinct sections of the reservoir bottom core, but not the bridge monolith, are dominated by non-planktonic diatoms. We attribute the occurrences of these phases to inflows that occur following heavy catchment rains at times when the reservoir is drawn down. These characteristic sections have, in turn, been used to refine the site's chronology. Despite having a length of almost 1.3 m, a variety of data suggests that the core has not recovered pre-reservoir sediment, but rather spans the period from 1981 (11 years after first filling) to 2001, when the core was extracted. It is clear, therefore, that sediments in the bottom of the reservoir are accumulating rapidly (>7 cm year-1), although more than 40% of this deposition occurs in less than 5% of the time. It appears that in the period 1996-2001, quiescent sedimentation rates, both in the perched bridge locality and on the reservoir bottom, slowed in response to reduced stream flow. Our findings indicate that, with caution, complex patterns of sedimentation in water storages can be disentangled. However, it was difficult to precisely correlate diatom sequences from the two records even in periods of quiescent sedimentation, suggesting that reservoir bottom diatom sequences should be interpreted with considerable caution. Furthermore, while storm-derived inflows such as those identified may deliver a substantial proportion of sediment and phosphorus load to storages, the ensuing deposition patterns may render much of the phosphorus unavailable to the overlying waters. © 2009 Springer Science+Business Media B.V.
- Authors: Tibby, John , Gell, Peter , Hancock, Gary , Clark, M.
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. , no. (2009), p. 1-15
- Full Text:
- Reviewed:
- Description: Despite their direct links to human use, reservoirs are not widely utilised, relative to natural lakes, for deriving sediment histories. One explanation is the complex sedimentation patterns observed in water storages. Here a highly unusual combination of sedimentary records is used to determine the sedimentation history of Kangaroo Creek Reservoir, South Australia. We compare contiguous high resolution (0.5 cm sampling interval) diatom records from an almost 1.3 m core extracted from the bottom of the reservoir and from a 0.4 m monolith of sediment perched 15 m above the reservoir bottom on a disused bridge that was submerged following initial reservoir filling in 1970. The diatom histories are supplemented by evidence provided by other indicators, most notably radionuclide concentrations and ratios. Interestingly, despite the fact that the reservoir has been >20 m deep for more than 70% of its recorded history, distinct sections of the reservoir bottom core, but not the bridge monolith, are dominated by non-planktonic diatoms. We attribute the occurrences of these phases to inflows that occur following heavy catchment rains at times when the reservoir is drawn down. These characteristic sections have, in turn, been used to refine the site's chronology. Despite having a length of almost 1.3 m, a variety of data suggests that the core has not recovered pre-reservoir sediment, but rather spans the period from 1981 (11 years after first filling) to 2001, when the core was extracted. It is clear, therefore, that sediments in the bottom of the reservoir are accumulating rapidly (>7 cm year-1), although more than 40% of this deposition occurs in less than 5% of the time. It appears that in the period 1996-2001, quiescent sedimentation rates, both in the perched bridge locality and on the reservoir bottom, slowed in response to reduced stream flow. Our findings indicate that, with caution, complex patterns of sedimentation in water storages can be disentangled. However, it was difficult to precisely correlate diatom sequences from the two records even in periods of quiescent sedimentation, suggesting that reservoir bottom diatom sequences should be interpreted with considerable caution. Furthermore, while storm-derived inflows such as those identified may deliver a substantial proportion of sediment and phosphorus load to storages, the ensuing deposition patterns may render much of the phosphorus unavailable to the overlying waters. © 2009 Springer Science+Business Media B.V.
- Description: Despite their direct links to human use, reservoirs are not widely utilised, relative to natural lakes, for deriving sediment histories. One explanation is the complex sedimentation patterns observed in water storages. Here a highly unusual combination of sedimentary records is used to determine the sedimentation history of Kangaroo Creek Reservoir, South Australia. We compare contiguous high resolution (0.5 cm sampling interval) diatom records from an almost 1.3 m core extracted from the bottom of the reservoir and from a 0.4 m monolith of sediment perched 15 m above the reservoir bottom on a disused bridge that was submerged following initial reservoir filling in 1970. The diatom histories are supplemented by evidence provided by other indicators, most notably radionuclide concentrations and ratios. Interestingly, despite the fact that the reservoir has been >20 m deep for more than 70% of its recorded history, distinct sections of the reservoir bottom core, but not the bridge monolith, are dominated by non-planktonic diatoms. We attribute the occurrences of these phases to inflows that occur following heavy catchment rains at times when the reservoir is drawn down. These characteristic sections have, in turn, been used to refine the site's chronology. Despite having a length of almost 1.3 m, a variety of data suggests that the core has not recovered pre-reservoir sediment, but rather spans the period from 1981 (11 years after first filling) to 2001, when the core was extracted. It is clear, therefore, that sediments in the bottom of the reservoir are accumulating rapidly (>7 cm year-1), although more than 40% of this deposition occurs in less than 5% of the time. It appears that in the period 1996-2001, quiescent sedimentation rates, both in the perched bridge locality and on the reservoir bottom, slowed in response to reduced stream flow. Our findings indicate that, with caution, complex patterns of sedimentation in water storages can be disentangled. However, it was difficult to precisely correlate diatom sequences from the two records even in periods of quiescent sedimentation, suggesting that reservoir bottom diatom sequences should be interpreted with considerable caution. Furthermore, while storm-derived inflows such as those identified may deliver a substantial proportion of sediment and phosphorus load to storages, the ensuing deposition patterns may render much of the phosphorus unavailable to the overlying waters. © 2009 Springer Science+Business Media B.V.
The palaeolimnological record from lake Cullulleraine, lower Murray River (south-east Australia) : Implications for understanding riverine histories
- Fluin, J., Tibby, John, Gell, Peter
- Authors: Fluin, J. , Tibby, John , Gell, Peter
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. , no. (2009), p. 1-14
- Full Text:
- Reviewed:
- Description: Australia's largest river system, the Murray-Darling Basin, is the focus of scientific and political attention, due mainly to the competing issues of economic productivity versus environmental flows. Central to this dialogue is the need to know about the Basin's natural condition and the degree to which the system has deviated from this pre-disturbance, baseline status. This study examines the patterns of ecological change in Lake Cullulleraine, a permanently connected artificial wetland adjacent to Lock Nine on the Murray River, south-east Australia. A 43-cm sediment core was collected in January 1998 and diatoms were analysed at 1-cm intervals for use as aquatic ecological indicators. The sediment core was dated using 210Pb. Changes in the diatom community have occurred since the time of lake formation in 1926, particularly shifts between Aulacoseira subborealis, Staurosira construens var. venter, Aulacoseira granulata, Staurosirella pinnata and Pseudostaurosira brevistriata. An electrical conductivity (EC) transfer function was applied to the fossil diatom assemblages and inferred EC values were compared to long-term, historical EC data from the River. Despite the presence of good analogues between fossil and modern diatom assemblages, inferred EC did not reflect measured EC accurately. In recent decades, patterns in the two data sets were reversed. Despite clear changes in the fossil record, quantitative palaeo-environmental interpretation was limited because the dominant taxa occupy broad ecological niches. Despite these limitations, changes in the Lake Cullulleraine record, particularly in the planktonic taxa, can be interpreted in terms of landscape change. Furthermore, because of the good chronology from the site, the record may be useful for dating changes observed in sites with poor chronological control. © 2009 Springer Science+Business Media B.V.
- Authors: Fluin, J. , Tibby, John , Gell, Peter
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. , no. (2009), p. 1-14
- Full Text:
- Reviewed:
- Description: Australia's largest river system, the Murray-Darling Basin, is the focus of scientific and political attention, due mainly to the competing issues of economic productivity versus environmental flows. Central to this dialogue is the need to know about the Basin's natural condition and the degree to which the system has deviated from this pre-disturbance, baseline status. This study examines the patterns of ecological change in Lake Cullulleraine, a permanently connected artificial wetland adjacent to Lock Nine on the Murray River, south-east Australia. A 43-cm sediment core was collected in January 1998 and diatoms were analysed at 1-cm intervals for use as aquatic ecological indicators. The sediment core was dated using 210Pb. Changes in the diatom community have occurred since the time of lake formation in 1926, particularly shifts between Aulacoseira subborealis, Staurosira construens var. venter, Aulacoseira granulata, Staurosirella pinnata and Pseudostaurosira brevistriata. An electrical conductivity (EC) transfer function was applied to the fossil diatom assemblages and inferred EC values were compared to long-term, historical EC data from the River. Despite the presence of good analogues between fossil and modern diatom assemblages, inferred EC did not reflect measured EC accurately. In recent decades, patterns in the two data sets were reversed. Despite clear changes in the fossil record, quantitative palaeo-environmental interpretation was limited because the dominant taxa occupy broad ecological niches. Despite these limitations, changes in the Lake Cullulleraine record, particularly in the planktonic taxa, can be interpreted in terms of landscape change. Furthermore, because of the good chronology from the site, the record may be useful for dating changes observed in sites with poor chronological control. © 2009 Springer Science+Business Media B.V.
- Tibby, John, Gell, Peter, Fluin, J., Sluiter, Ian
- Authors: Tibby, John , Gell, Peter , Fluin, J. , Sluiter, Ian
- Date: 2007
- Type: Text , Journal article
- Relation: Hydrobiologia Vol. 591, no. 1 (2007), p. 207-218
- Full Text:
- Description: Diatoms 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, diatom-conductivity relationships in eight seasonally monitored wetlands have been investigated. In developing a diatom-conductivity 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 (5-6 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).
Changing fluxes of sediments and salts as recorded in lower River Murray wetlands, Australia
- Gell, Peter, Fluin, Jennie, Tibby, John, Haynes, Deborah, Khanum, Syeda, Walsh, Brendan, Hancock, Gary, Harrison, Jennifer, Zawadzki, Atun, Little, Fiona
- Authors: Gell, Peter , Fluin, Jennie , Tibby, John , Haynes, Deborah , Khanum, Syeda , Walsh, Brendan , Hancock, Gary , Harrison, Jennifer , Zawadzki, Atun , Little, Fiona
- Date: 2006
- Type: Conference proceedings
- Full Text:
- Description: The River Murray basin, Australia's largest, has been significantly impacted by changed flow regimes and increased fluxes of salts and sediments since settlement in the 1840s. The river's flood plain hosts an array of cut-off meanders, levee lakes and basin depression lakes that archive historical changes. Pre-European sedimentation rates are typically approx. 0.1-1 mm year-1, while those in the period after European arrival are typically 10 to 30 fold greater. This increased sedimentation corresponds to a shift in wetland trophic state from submerged macrophytes in clear waters to phytoplankton-dominated, turbid systems. There is evidence for a decline in sedimentation in some natural wetlands after river regulation from the 1920s, but with the maintenance of the phytoplankton state. Fossil diatom assemblages reveal that, while some wetlands had saline episodes before settlement, others became saline after, and as early as the 1880s. The oxidation of sulphurous salts deposited after regulation has induced hyperacidity in a number of wetlands in recent years. While these wetlands are rightly perceived as being heavily impacted, other, once open water systems, that have infilled and now support rich macrophyte beds, are used as interpretive sites. The rate of filling, however, suggests that the lifespan of these wetlands is short. The rate of wetland loss through such increased infilling is unlikely to be matched by future scouring as regulation has eliminated middle order floods from the lower catchment.
- Authors: Gell, Peter , Fluin, Jennie , Tibby, John , Haynes, Deborah , Khanum, Syeda , Walsh, Brendan , Hancock, Gary , Harrison, Jennifer , Zawadzki, Atun , Little, Fiona
- Date: 2006
- Type: Conference proceedings
- Full Text:
- Description: The River Murray basin, Australia's largest, has been significantly impacted by changed flow regimes and increased fluxes of salts and sediments since settlement in the 1840s. The river's flood plain hosts an array of cut-off meanders, levee lakes and basin depression lakes that archive historical changes. Pre-European sedimentation rates are typically approx. 0.1-1 mm year-1, while those in the period after European arrival are typically 10 to 30 fold greater. This increased sedimentation corresponds to a shift in wetland trophic state from submerged macrophytes in clear waters to phytoplankton-dominated, turbid systems. There is evidence for a decline in sedimentation in some natural wetlands after river regulation from the 1920s, but with the maintenance of the phytoplankton state. Fossil diatom assemblages reveal that, while some wetlands had saline episodes before settlement, others became saline after, and as early as the 1880s. The oxidation of sulphurous salts deposited after regulation has induced hyperacidity in a number of wetlands in recent years. While these wetlands are rightly perceived as being heavily impacted, other, once open water systems, that have infilled and now support rich macrophyte beds, are used as interpretive sites. The rate of filling, however, suggests that the lifespan of these wetlands is short. The rate of wetland loss through such increased infilling is unlikely to be matched by future scouring as regulation has eliminated middle order floods from the lower catchment.
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