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Dissolved organic carbon dynamics in a large lowland river

Darren Baldwin1, Kerry Whitworth2, Andrew Keough3
1 CSIRO and the Murray-Darling Freshwater Research Centre
2 La trobe University and The Murray-Darling Freshwater Research Centre
3 Murray-Darling Basin Authority

O 7.7 in Controls of dissolved organic matter fluxes in ecosystems

14.07.2014, 15:55-16:15, H19

The functioning of lowland river-floodplain ecosystems depends on the two-way exchange of water, nutrients and energy during flood events.  In particular, carbon export from floodplains during flood events is an important energy subsidy for lowland rivers.  However, the export of carbon from the river channel can also cause some significant disbenefits. Following a decade-long drought, substantial areas of floodplains in the southern Murray-Darling Basin in south-eastern Australia were flooded in the austral summer of 2010/2011.  The floods mobilised several hundred thousand tonnes of dissolved organic carbon from river floodplains. Microbial metabolism of this carbon resulted in prolonged river hypoxia, lasting up to six months, and affecting over 2000 km of river channel.  In this paper we use data from this event, combined with laboratory experiments to explore the biogeochemical and hydrological factors that affect the mobilisation, transport and assimilation of dissolved organic carbon in a large lowland river ecosystem during floods.  Based on these studies we have developed a process-based model that predicts the fate of DOC during flooding as well as the resulting change in dissolved oxygen.  This model also allows hind-casting of carbon dynamics in the absence of the extensive river regulation that now occurs in the southern Murray-Darling Basin.  



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last modified 2014-06-17