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Ning N.S.P.,The Murray Darling Freshwater Research Center | Ning N.S.P.,La Trobe University | Watkins S.C.,The Murray Darling Freshwater Research Center | Watkins S.C.,La Trobe University | And 4 more authors.
Journal of Environmental Management

Water sharing to meet both agricultural and environmental demands is a critical issue affecting the health of many floodplain river systems around the world. This study explored the potential for using wetlands as temporary off-river storages to conjunctively maintain ecological values and support agricultural demands by assessing the effects of artificial drawdown on wetland aquatic plant communities. An initial experiment was undertaken in outdoor mesocosms in which four different treatments were compared over a 131 day duration: (1) natural drawdown where the water was left to drawdown naturally via evaporation; (2) partial drawdown where approximately half of the volume of water was pumped out after 42 days; (3) stepped drawdown where approximately half of the volume of water pumped out after 42 days, and then the remaining volume of water was pumped out after 117 days; and (4) total drawdown where all of the of water was pumped out after 117 days. A complementary field study was subsequently undertaken where two wetlands were left to drawdown naturally and two were partially drawn down artificially (i.e. had approximately half of their volume removed by pumping). Results from both of these studies indicated that neither aquatic plant abundance nor taxon richness were adversely affected by partial drawdown. Rather, both studies showed that aquatic plant communities subjected to a partial drawdown treatment became more species rich and diverse than communities subjected to a natural drawdown treatment. This suggests that it may be possible to use wetlands as intermediary storages for the dual purposes of maintaining ecological values and supporting agricultural demands. © 2012. Source

Whitworth K.L.,The Murray Darling Freshwater Research Center | Whitworth K.L.,La Trobe University | Baldwin D.S.,The Murray Darling Freshwater Research Center | Baldwin D.S.,CSIRO | And 2 more authors.
Journal of Hydrology

Hypoxic blackwater events are characterised by high levels of dissolved organic carbon in the water column, the metabolism of which depletes dissolved oxygen, which can cause fish and crustacean mortality. Understanding the drivers of and controls on hypoxic blackwater events is important in order to reduce the potential for detrimental water quality impacts from both managed and natural flows. After a decade-long drought in south-eastern Australia, a series of spring and summer flood events in 2010-2011 resulted in a large-scale hypoxic blackwater event in the southern Murray-Darling Basin that affected over 2000. km of river channels and persisted for 6. months. We examined the biogeochemistry and hydrology underpinning this extreme event and found that multiple drivers contributed to the development and persistence of hypoxic blackwater. Inundation of both forested and agricultural floodplains that had not been flooded for over a decade mobilised large stores of reactive carbon. Altered flow seasonality, due to a combination of climatic effects and river regulation, not only increased the risk of hypoxic blackwater generation but also shifted the proportion of bioavailable carbon that was returned to the river channels. Hypolimnetic weir discharge also contributed to hypoxia at some sites. These findings highlight the need for a whole-of-system perspective for the management of regulated river systems - especially in the face of a changing climate. © 2012. Source

King A.J.,Charles Darwin University | King A.J.,Arthur Rylah Institute for Environmental Research | Gawne B.,The Murray Darling Freshwater Research Center | Gawne B.,La Trobe University | And 6 more authors.
Environmental Management

Environmental flows are now an important restoration technique in flow-degraded rivers, and with the increasing public scrutiny of their effectiveness and value, the importance of undertaking scientifically robust monitoring is now even more critical. Many existing environmental flow monitoring programs have poorly defined objectives, nonjustified indicator choices, weak experimental designs, poor statistical strength, and often focus on outcomes from a single event. These negative attributes make them difficult to learn from. We provide practical recommendations that aim to improve the performance, scientific robustness, and defensibility of environmental flow monitoring programs. We draw on the literature and knowledge gained from working with stakeholders and managers to design, implement, and monitor a range of environmental flow types. We recommend that (1) environmental flow monitoring programs should be implemented within an adaptive management framework; (2) objectives of environmental flow programs should be well defined, attainable, and based on an agreed conceptual understanding of the system; (3) program and intervention targets should be attainable, measurable, and inform program objectives; (4) intervention monitoring programs should improve our understanding of flow-ecological responses and related conceptual models; (5) indicator selection should be based on conceptual models, objectives, and prioritization approaches; (6) appropriate monitoring designs and statistical tools should be used to measure and determine ecological response; (7) responses should be measured within timeframes that are relevant to the indicator(s); (8) watering events should be treated as replicates of a larger experiment; (9) environmental flow outcomes should be reported using a standard suite of metadata. Incorporating these attributes into future monitoring programs should ensure their outcomes are transferable and measured with high scientific credibility. © 2015, Springer Science+Business Media New York. Source

Nielsen D.L.,CSIRO | Nielsen D.L.,The Murray Darling Freshwater Research Center | Nielsen D.L.,La Trobe University | Gigney H.,CSIRO | And 5 more authors.

Slackwater habitats within lowland rivers support abundant biotic communities and provide these communities with a refuge from increases in discharge. These refuges allow biota to persist as discharges, vary and provide a source of colonists for slackwaters further downstream. In order to investigate the response of slackwater benthic microfaunal communities to changes in discharge, artificial slackwaters were created within the main channel of a lowland river and benthic microfaunal communities were sampled over a 60-day period. Benthic microfauna within the artificial and reference slackwaters were recorded in higher richness and abundance than in the main river channel. Within days the communities in the artificial slackwaters were similar to those in the reference slackwaters. The rapid speed of colonisation suggests that initial colonisation of slackwaters is likely to occur via active or passive dispersal of biota and that these systems and communities are resilient to changes in discharge. © Springer Science+Business Media B.V. 2009. Source

Ning N.S.P.,The Murray Darling Freshwater Research Center | Ning N.S.P.,La Trobe University | Hladyz S.,The Murray Darling Freshwater Research Center | Hladyz S.,CSIRO | And 8 more authors.
Journal of Fish Biology

Morphological (growth, Fulton's condition factor), physiological (per cent dry mass, total lipid content) and behavioural (activity levels) response patterns of carp gudgeon Hypseleotris spp. were examined in response to food deprivation during a 56 day experiment. Considerable variability in the nature and magnitude of these response patterns was observed, suggesting that caution should be taken when interpreting changes in the health of small-bodied fishes based on individual response variables. © 2011 The Fisheries Society of the British Isles. Source

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