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:
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- 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.
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
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- 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.
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
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- 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.
- Grundell, Rosie, Gell, Peter, Mills, Keely, Zawadzki, Atun
- Authors: Grundell, Rosie , Gell, Peter , Mills, Keely , Zawadzki, Atun
- Date: 2012
- Type: Text , Journal article
- Relation: Journal of Paleolimnology Vol. 47, no. 2 (2012), p. 205-219
- Full Text: false
- Reviewed:
- Description: Sinclair Flat is small wetland, located within the gorge section of the Murray River floodplain. situated near Blanchetown, South Australia, the wetland is closely linked to the River and, since regulation, has become permanently inundated. High summer evaporation rates deplete the volume of water within the wetland. However, this is compensated by perennial inflow via a permanent inlet from the River. This site provides an opportunity to explore the relative contribution of river and wetland diatom flora to the sediment record, and the fluvial and aerial contribution of radiometric isotopes to the system. The geochronological and biostratigraphic data provide an insight into the history of the water quality of Sinclair Flat. Evidence exists for the River being a source of sediments and isotopes and of diatom species typical of the main river channel. Prior to 1950, Sinclair Flat was an oligotrophic, oligosaline, clear-water wetland. The wetland shifted gradually to an environment that favoured clear-water benthic species, most likely as a consequence of changes following river regulation in the 1920s, although the capacity to date these sediments is limited. During the 1950s, the wetland became plankton dominated. Peaks in epiphytic diatoms during the 1960s suggest increased emergent macrophyte cover. The contemporary condition is of a connected, turbid, eutrophic and mesosaline lagoon. The ecological condition of Sinclair Flat has diverged considerably from its historical range of condition. This record supports evidence from upstream of widespread state switches in the Murray-Darling Basin floodplain wetlands. This record also lends considerable weight to modern studies attesting to the degraded state of the waterways of the Murray-Darling Basin and the impact of river regulation practices on the water quality of these ecosystems. © 2011 Springer Science+Business Media B.V.
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