- MacGregor, Angus, Gell, Peter, Wallbrink, Peter, Hancock, Gary
- Authors: MacGregor, Angus , Gell, Peter , Wallbrink, Peter , Hancock, Gary
- Date: 2005
- Type: Journal article
- Relation: River Research and Applications Vol. 21, no. 2-3 (2005), p. 201-213
- Full Text: false
- Reviewed:
- Description: Millennial to decadal resolution palaeoenvironmental records from the terminal floodplain lakes of the lower Snowy River in eastern Victoria have been obtained to determine the water quality history of the lower Snowy River floodplain and more specifically, the ecological impact of the inter-basin diversion of water from one of Australia's hallmark river systems. Lake Curlip, as evidenced through variations in the fossil-diatom flora, has evolved through the Holocene from a saline (17-22 g salt/l) open system (c. 7000 years BP) as sea levels reached their maxima, to a brackish (5-10 g/l), and then a fresh (as low as 0.4 g/l), possibly acidic system prior to European settlement (c. 300 years BP). The upper post-European sediments reveal a complex, highly variable, anthropogenically induced shift to a brackish and nutrient-tolerant diatom flora, with recent diatom-inferred salinities in the order of 20 g/l. Explained as a combination of land clearance, drainage practices, and more recently, the regulation of the Snowy River, recent changes are as pronounced as any experienced through the Holocene, but have occurred at a rate faster than any brought on by past climatic or geomorphic change. By quantifying the limnological changes before and after regulation this study informs on the relative benefits that may accrue from allocating environmental flows to the Snowy River. Copyright © 2005 John Wiley & Sons, Ltd.
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.
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).
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.
- 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.
- Atazadeh, Islam, Edlund, Mark, Van Der Vijver, Bart, Mills, Keely, Spaulding, Sarah, Gell, Peter, Crawford, Simon, Barton, Andrew, Lee, Sylvia, Smith, Kathryn, Newall, Peter, Potapova, Maria
- Authors: Atazadeh, Islam , Edlund, Mark , Van Der Vijver, Bart , Mills, Keely , Spaulding, Sarah , Gell, Peter , Crawford, Simon , Barton, Andrew , Lee, Sylvia , Smith, Kathryn , Newall, Peter , Potapova, Maria
- Date: 2014
- Type: Text , Journal article
- Relation: Diatom Research Vol. 29, no. 4 (2014), p. 455-464
- Full Text: false
- Reviewed:
- Description: Stauroneis pachycephala was described in 1881 from the Baakens River, Port Elizabeth, South Africa. Recently, it was found during surveys of the MacKenzie River (Victoria, Australia), the Florida Everglades (USA) and coastal marshes of Louisiana (USA). The morphology, ecology and geographic distribution of this species are described in this article. This naviculoid species is characterised by lanceolate valves with a gibbous centre, a sigmoid raphe, an axial area narrowing toward the valve ends, and capitate valve apices. The central area is a distinct stauros that is slightly widened near the valve margin. The raphe is straight and filiform, and the terminal raphe fissures are strongly deflected in opposite directions. Striae are fine and radiate in the middle of the valve, becoming parallel and eventually convergent toward the valve ends. The external surface of the valves and copulae is smooth and lacks ornamentation. We also examined the type material of S. pachycephala. Our observations show this species has morphological characteristics that fit within the genus Envekadea. Therefore, the transfer of S. pachycephala to Envekadea is proposed and a lectotype is designated.
- Description: C1
- 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.
- Greenslade, Penelope, Florentine, Singarayer, Hansen, Birgita, Gell, Peter
- Authors: Greenslade, Penelope , Florentine, Singarayer , Hansen, Birgita , Gell, Peter
- Date: 2016
- Type: Text , Journal article
- Relation: Environmental Monitoring and Assessment Vol. 188, no. 8 (2016), p. 1-9
- Full Text: false
- Reviewed:
- Description: Monitoring forms the basis for understanding ecological change. It relies on repeatability of methods to ensure detected changes accurately reflect the effect of environmental drivers. However, operator bias can influence the repeatability of field and laboratory work. We tested this for invertebrates and diatoms in three trials: (1) two operators swept invertebrates from heath vegetation, (2) four operators picked invertebrates from pyrethrum knockdown samples from tree trunk and (3) diatom identifications by eight operators in three laboratories. In each trial, operators were working simultaneously and their training in the field and laboratory was identical. No variation in catch efficiency was found between the two operators of differing experience using a random number of net sweeps to catch invertebrates when sequence, location and size of sweeps were random. Number of individuals and higher taxa collected by four operators from tree trunks varied significantly between operators and with their ‘experience ranking’. Diatom identifications made by eight operators were clustered together according to which of three laboratories they belonged. These three tests demonstrated significant potential bias of operators in both field and laboratory. This is the first documented case demonstrating the significant influence of observer bias on results from invertebrate field-based studies. Examples of two long-term trials are also given that illustrate further operator bias. Our results suggest that long-term ecological studies using invertebrates need to be rigorously audited to ensure that operator bias is accounted for during analysis and interpretation. Further, taxonomic harmonisation remains an important step in merging field and laboratory data collected by different operators. © 2016, Springer International Publishing Switzerland.
- Authors: Gell, Peter
- Date: 2017
- Type: Text , Book chapter
- Relation: Applications of paleoenvironmental techniques in estuarine studies (Developments in Paleoenvironmental Research series) Chapter 23 p. 587-613
- Full Text: false
- Reviewed:
- Description: The Coorong is a back-barrier lagoon that lies at the mouth of the Murray-Darling Basin, Australia. As part of a wider estuarine complex it was successfully nominated as a wetland of international significance under the Ramsar Convention where it was identified as a saline to hypersaline lagoon. Perceived obligations to retain this condition lead to limits on the release of freshwater from the hinterland to the lagoon. The Coorong has been identified as at risk of degradation with declining cover of its primary autotroph Ruppia spp. attributed to increasing salinity. Declining flows through the Murray-Darling Basin and recent drought induced extreme hypersalinity, particularly in the south lagoon. Increases in brine shrimp, declines in its fishery and replacement of a diverse avifauna with Banded Stilt led to calls that the Coorong was in crisis. Diatom-based palaeoecological assessment along the length of the lagoon revealed a natural subsaline, tidal system that shifted, after the commissioning of barrages, to a saline, closed lagoon with extensive sulphidic sediments. The misidentification of the natural character of the lagoon accentuated its degradation. Earlier sediment-based research may have provided for the identification of a more appropriate natural ecological character and an early warning of the degree to which the system had degraded. Palaeolimnological approaches represent a valuable tool to better evaluate the condition of wetlands listed under the Ramsar Convention.
- Soeprobowati, Tri, Suedy, Sri, Hadiyanto, Lubis, Ali, Gell, Peter
- Authors: Soeprobowati, Tri , Suedy, Sri , Hadiyanto , Lubis, Ali , Gell, Peter
- Date: 2018
- Type: Text , Journal article
- Relation: Environmental Technology and Innovation Vol. 10, no. (2018), p. 314-323
- Full Text: false
- Reviewed:
- Description: Lake Warna is a small shallow crater lake on the Dieng Plateau, Central Java, the second highest plateau in the world after Nepal. A 24 cm sediment core was extracted from Lake Warna to reconstruct environmental changes in the Lake and its catchment from preserved diatom assemblages. Diatoms are microalgae in the Bacillariophyte that have silicious cell walls that can be preserved in sediments. As diatom species are sensitive to water quality changes in the assemblages upcore reflect changes in lake condition. Sediment cores were collected from two sites, sliced at 1 cm intervals for diatom analysis and bulked across 3 cm for 210Pb radiometric dating. Examination of diatoms in a 24 cm sediment core from Lake Warna reveals clear correlation with human activities in the catchment area over the past 124 years. The record is divided into 2 zones based on sustained changes in the diatom assemblages. The lowest zone Zone I (21–15 cm, estimated 1935–1954) was dominated by Frustulia crassinervia (Brebisson ex W. Smith) Ross, Gomph onema parvulum (Kutzing) Kutzing, Pinnularia valdetolerans Mayama & H. Kobayasi, P. viridis (Nitzsch) Ehrenberg, and Aulacoseira distans (Ehrenberg) Simonson. Zone II (15–0 cm, estimated 1980–2013), the uppermost zone was dominated by P. viridiformis Krammer, P. latevittata Cleve, E. monodon var. tro p ica (Hustedt) Hustedt, S. seminulum Grunow, P a crosphaeria W. Smith. E. zygodon Ehrenberg, P. gibba Ehrenberg, and P. viridiformis Krammer. The 15 cm core from TW3 commenced sediment accumulation 114 years ago and is divided into 2 zones as well. Zone I (15–7 cm, estimated 1901–1981) was dominated by Brachysira brebissonii R. Ross, G. parvulum (Kutzing) Kutzing, E. monodon var. tropica (Hustedt) Hustedt, E. zygodon Ehrenberg and S. seminulum Grunow. Zone II (7–0 cm, estimated 1981–2006) was dominated by P. viridiformis Krammer, P. gibba Ehrenberg, Pinnularia viridis (Nitzsch) Ehrenberg, Sellaphora bacillum (Ehrenberg) Mann, S. seminulum Grunow, and Stauroneis sp. These assemblages reflect ongoing acid, clear water conditions for the time represented by the cores. The recent rise in S. seminulum Grunow reflects recent lake eutrophication likely owing to the accelerated agricultural and urban development in the lake's catchment in recent decades.
- Reeves, Jessica, Gell, Peter, Reichman, Suzie, Trewarn, Adam, Zawadzki, Atun
- Authors: Reeves, Jessica , Gell, Peter , Reichman, Suzie , Trewarn, Adam , Zawadzki, Atun
- Date: 2016
- Type: Text , Journal article
- Relation: Marine and Freshwater Research Vol. 67, no. 6 (2016), p. 837-849
- Full Text: false
- Reviewed:
- Description: Around the globe, heavy industry has often been associated with estuaries, which provide water for operations, waste disposal and navigation. Many of these practices leave a legacy of contamination, which accumulate in the estuaries, which act as sediment sinks. Heavy metal contaminants may remain buried, even after the industrial practices are ceased. The Connewarre Complex is a series of wetlands, within the Port Philip and Bellarine Ramsar site. Through a unique combination of techniques, including diatom assemblages, biogeochemistry (δ13C, δ15N, C/N) and heavy metal content, the major anthropogenic influences over the last 170 years and the biotic response has been determined. Key features that can be elucidated include regulation of the waterways, establishment of heavy industry and major shifts in climatic conditions. In combination, these drivers have acted to rapidly shift the condition of the wetland from early in settlement such that the perceived 'natural ecological character' is actually an artificial one. The legacy of contamination is common to many Ramsar-listed wetlands. The lesson from this site is that, when making plans to manage the ecological condition of a wetland, past use needs to be considered to ensure that well meaning interventions do not exacerbate risk of mobilising contaminants best left undisturbed. Journal compilation © CSIRO 2016.
Ecological response to hydrological variability and catchment development : Insights from a shallow oxbow lake in Lower Mississippi Valley, Arkansas
- Bhattacharya, Ruchi, Hausmann, Sonja, Hubeny, J. Bradford, Gell, Peter, Black, Jessica
- Authors: Bhattacharya, Ruchi , Hausmann, Sonja , Hubeny, J. Bradford , Gell, Peter , Black, Jessica
- Date: 2016
- Type: Text , Journal article
- Relation: Science of the Total Environment Vol. 569-570, no. (2016), p. 1087-1097
- Full Text:
- Reviewed:
- Description: The ecological response of shallow oxbow lakes to variability in hydrology and catchment development in large river floodplain ecosystems (RFE) in Arkansas remains largely unknown. Investigating these responses will advance our understanding of ecological evolution of oxbow lakes in response to the major environmental drivers, which will establish baseline conditions required to develop effective management practices for RFE. In this pilot study, we examined the potential of using a dated surface sediment core from Adams Bayou, a floodplain lake located within the Cache-Lower White River Ramsar site in SE Arkansas. Stratigraphic records of diatoms and sediment geochemistry were used to ascertain variation in Adams Bayou's ecological condition. During 1968–2008, in response to hydrological and anthropogenic changes, Adams Bayou's diatom assemblages progressed from predominantly benthic (Gomphonema parvulum and Meridion circulare) to primarily planktonic assemblage (Aulacoseira granulata and Cyclotella meneghiniana), along with a decrease in magnetic susceptibility (k) and % silt. Statistical analyses reveled that during 1968–2000, higher hydrological connectivity and catchment alterations drove Adams Bayou's ecosystem. After 2000, lower hydrological connectivity and increase in cultivation were the major drivers. The potential impact of increasing air temperature was also noted. The shift in Adams Bayou from a connected, clear, mesotrophic state to a relatively isolated, turbid and nutrient enriched state is consistent with regime shift models and highlights its sensitivity to a combination of environmental stresses prevalent in the catchment. Although fluvial systems pose challenges in establishing clear chronologies, oxbow lake sediments can be a effective paleoecological archives. Our work provides clear evidence for the change in the ecological character of this wetland of international significance and flags the need for a wider assessment of water bodies across this site under obligations to the Ramsar Convention.
- Description: The ecological response of shallow oxbow lakes to variability in hydrology and catchment development in large river floodplain ecosystems (RFE) in Arkansas remains largely unknown. Investigating these responses will advance our understanding of ecological evolution of oxbow lakes in response to the major environmental drivers, which will establish baseline conditions required to develop effective management practices for RFE. In this pilot study, we examined the potential of using a dated surface sediment core from Adams Bayou, a floodplain lake located within the Cache-Lower White River Ramsar site in SE Arkansas. Stratigraphic records of diatoms and sediment geochemistry were used to ascertain variation in Adams Bayou's ecological condition. During 1968–2008, in response to hydrological and anthropogenic changes, Adams Bayou's diatom assemblages progressed from predominantly benthic (Gomphonema parvulum and Meridion circulare) to primarily planktonic assemblage (Aulacoseira granulata and Cyclotella meneghiniana), along with a decrease in magnetic susceptibility (k) and % silt. Statistical analyses reveled that during 1968–2000, higher hydrological connectivity and catchment alterations drove Adams Bayou's ecosystem. After 2000, lower hydrological connectivity and increase in cultivation were the major drivers. The potential impact of increasing air temperature was also noted. The shift in Adams Bayou from a connected, clear, mesotrophic state to a relatively isolated, turbid and nutrient enriched state is consistent with regime shift models and highlights its sensitivity to a combination of environmental stresses prevalent in the catchment. Although fluvial systems pose challenges in establishing clear chronologies, oxbow lake sediments can be a effective paleoecological archives. Our work provides clear evidence for the change in the ecological character of this wetland of international significance and flags the need for a wider assessment of water bodies across this site under obligations to the Ramsar Convention. © 2016 Elsevier B.V.
- Authors: Bhattacharya, Ruchi , Hausmann, Sonja , Hubeny, J. Bradford , Gell, Peter , Black, Jessica
- Date: 2016
- Type: Text , Journal article
- Relation: Science of the Total Environment Vol. 569-570, no. (2016), p. 1087-1097
- Full Text:
- Reviewed:
- Description: The ecological response of shallow oxbow lakes to variability in hydrology and catchment development in large river floodplain ecosystems (RFE) in Arkansas remains largely unknown. Investigating these responses will advance our understanding of ecological evolution of oxbow lakes in response to the major environmental drivers, which will establish baseline conditions required to develop effective management practices for RFE. In this pilot study, we examined the potential of using a dated surface sediment core from Adams Bayou, a floodplain lake located within the Cache-Lower White River Ramsar site in SE Arkansas. Stratigraphic records of diatoms and sediment geochemistry were used to ascertain variation in Adams Bayou's ecological condition. During 1968–2008, in response to hydrological and anthropogenic changes, Adams Bayou's diatom assemblages progressed from predominantly benthic (Gomphonema parvulum and Meridion circulare) to primarily planktonic assemblage (Aulacoseira granulata and Cyclotella meneghiniana), along with a decrease in magnetic susceptibility (k) and % silt. Statistical analyses reveled that during 1968–2000, higher hydrological connectivity and catchment alterations drove Adams Bayou's ecosystem. After 2000, lower hydrological connectivity and increase in cultivation were the major drivers. The potential impact of increasing air temperature was also noted. The shift in Adams Bayou from a connected, clear, mesotrophic state to a relatively isolated, turbid and nutrient enriched state is consistent with regime shift models and highlights its sensitivity to a combination of environmental stresses prevalent in the catchment. Although fluvial systems pose challenges in establishing clear chronologies, oxbow lake sediments can be a effective paleoecological archives. Our work provides clear evidence for the change in the ecological character of this wetland of international significance and flags the need for a wider assessment of water bodies across this site under obligations to the Ramsar Convention.
- Description: The ecological response of shallow oxbow lakes to variability in hydrology and catchment development in large river floodplain ecosystems (RFE) in Arkansas remains largely unknown. Investigating these responses will advance our understanding of ecological evolution of oxbow lakes in response to the major environmental drivers, which will establish baseline conditions required to develop effective management practices for RFE. In this pilot study, we examined the potential of using a dated surface sediment core from Adams Bayou, a floodplain lake located within the Cache-Lower White River Ramsar site in SE Arkansas. Stratigraphic records of diatoms and sediment geochemistry were used to ascertain variation in Adams Bayou's ecological condition. During 1968–2008, in response to hydrological and anthropogenic changes, Adams Bayou's diatom assemblages progressed from predominantly benthic (Gomphonema parvulum and Meridion circulare) to primarily planktonic assemblage (Aulacoseira granulata and Cyclotella meneghiniana), along with a decrease in magnetic susceptibility (k) and % silt. Statistical analyses reveled that during 1968–2000, higher hydrological connectivity and catchment alterations drove Adams Bayou's ecosystem. After 2000, lower hydrological connectivity and increase in cultivation were the major drivers. The potential impact of increasing air temperature was also noted. The shift in Adams Bayou from a connected, clear, mesotrophic state to a relatively isolated, turbid and nutrient enriched state is consistent with regime shift models and highlights its sensitivity to a combination of environmental stresses prevalent in the catchment. Although fluvial systems pose challenges in establishing clear chronologies, oxbow lake sediments can be a effective paleoecological archives. Our work provides clear evidence for the change in the ecological character of this wetland of international significance and flags the need for a wider assessment of water bodies across this site under obligations to the Ramsar Convention. © 2016 Elsevier B.V.
Multiproxy approach to track changes in the ecological condition of wetlands in the Gunbower Forest, a Ramsar site
- Mall, Neeraj, Gell, Peter, Kattel, Giri, Gadd, Patricia, Zawadzki, Atun
- Authors: Mall, Neeraj , Gell, Peter , Kattel, Giri , Gadd, Patricia , Zawadzki, Atun
- Date: 2022
- Type: Text , Journal article
- Relation: Marine and Freshwater Research Vol. 73, no. 10 (2022), p. 1196-1211
- Full Text:
- Reviewed:
- Description: Gunbower Forest is bordered by the Murray River and Gunbower Creek and hosts several floodplain wetlands listed under the Ramsar Convention. Sediment cores were retrieved from three wetlands to trace changes to their ecological state over time. The basal sediments of the wetlands date back to the beginning of river regulation in the 1930s, suggesting that only after then were they inundated sufficiently often to allow for net sediment accumulation. The diatoms preserved in the lower levels of all cores suggest clear, freshwater conditions prevailed during that period. Increased sediment and nutrient loads are inferred by increased epiphytic forms and nutrient indicators. Over recent decades the wetlands have transitioned to plankton dominance, reflecting greater connectivity to the river and distributary, and a reduced light environment. This pattern resembles to that recorded both upstream and downstream, suggesting a regional-scale change in the wetlands of the southern Murray-Darling Basin. © CSIRO 2022.
- Authors: Mall, Neeraj , Gell, Peter , Kattel, Giri , Gadd, Patricia , Zawadzki, Atun
- Date: 2022
- Type: Text , Journal article
- Relation: Marine and Freshwater Research Vol. 73, no. 10 (2022), p. 1196-1211
- Full Text:
- Reviewed:
- Description: Gunbower Forest is bordered by the Murray River and Gunbower Creek and hosts several floodplain wetlands listed under the Ramsar Convention. Sediment cores were retrieved from three wetlands to trace changes to their ecological state over time. The basal sediments of the wetlands date back to the beginning of river regulation in the 1930s, suggesting that only after then were they inundated sufficiently often to allow for net sediment accumulation. The diatoms preserved in the lower levels of all cores suggest clear, freshwater conditions prevailed during that period. Increased sediment and nutrient loads are inferred by increased epiphytic forms and nutrient indicators. Over recent decades the wetlands have transitioned to plankton dominance, reflecting greater connectivity to the river and distributary, and a reduced light environment. This pattern resembles to that recorded both upstream and downstream, suggesting a regional-scale change in the wetlands of the southern Murray-Darling Basin. © CSIRO 2022.
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