A legacy of climate and catchment change: the real challenge for wetland management
- Authors: Gell, Peter , Mills, Keely , Grundell, Rosie
- Date: 2013
- Type: Text , Journal article
- Relation: Hydrobiologia Vol. 708, no. 1 (May 2013), p. 133-144
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- Description: Wetland managers are faced with an array of challenges when restoring ecosystems at risk from changing climate and human impacts, especially as many of these processes have been operating over decadal-millennial timescales. Variations in the level and salinity of the large crater lakes of western Victoria, as revealed over millennia by the physical, chemical and biological evidence archived in sediments, attest to extended periods of positive rainfall balance and others of rainfall deficit. The recent declines in the depth of these lakes have been attributed to a 15% decline in effective rainfall since AD 1859. Whilst some sites reveal state shifts following past droughts, the response of most wetlands to millennial-scale climatic variations is muted. Regional wetland condition has changed comprehensively, however, since European settlement, on account of extensive catchment modifications. These modifications appear to have reduced the resilience of wetlands limiting their capacity to recover from the recent 'big dry'. These sedimentary archives reveal most modern wetlands to be outside their historical range of variability. This approach provides a longer-term context when assessing wetland condition and better establishes the restoration challenge posed by the impact of climate change and variability and human impacts.
- Description: C1
Interaction between a river and its wetland : Evidence from the Murray River for spatial variability in diatom and radioisotope records
- 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
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- 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.
Tracking a century of change in trophic structure and dynamics in a floodplain wetland: Integrating palaeoecological and palaeoisotopic evidence
- Authors: Kattel, Giri , Gell, Peter , Perga, Marie-Elodie , Jeppesen, Erik , Grundell, Rosie , Weller, Sandra , Zawadzki, Atun , Barry, Linda
- Date: 2015
- Type: Text , Journal article
- Relation: Freshwater Biology Vol. 60, no. 4 (2015), p. 711-723
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- Description: The palaeoecological assessment, and the use of stable isotopes of carbon in subfossils of herbivores and omnivores, represents a novel approach to understand transitions in past food-web structure and the dynamics of lake ecosystems in response to natural perturbations and human impacts. Combined with records of subfossil assemblages of cladocerans and chironomids, it may be possible to decipher whether changes are attributable to external forces or internally derived system shifts. A sediment record taken from the shallow (2.3 m depth) Kings Billabong in the River Murray floodplain (Australia) was analysed to explore changes in trophic dynamics over the past century. The palaeoecological assessment revealed that littoral assemblages of cladocerans and benthic diatoms were gradually replaced by planktonic (planktonic and facultative planktonic) assemblages after river regulation in the 1920s. The stable isotopic composition of carbon (