Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

Changes in organic-matter dynamics and physicochemistry, associated with riparian vegetation loss and river regulation in floodplain wetlands of the Murray River, Australia

Susanne C. Watkins A B D , G. P. Quinn C and Ben Gawne B

A School of Biological Sciences, Monash University, Clayton, Vic. 3800, Australia.

B Present address: The Murray–Darling Freshwater Research Centre, La Trobe University, PO Box 991, Wodonga, Vic. 3689, Australia.

C School of Life and Environmental Sciences, Deakin University, Warrnambool, Vic. 3280, Australia.

D Corresponding author. Email:

Marine and Freshwater Research 61(10) 1207-1217
Submitted: 18 December 2009  Accepted: 22 May 2010   Published: 14 October 2010


Extensive clearing of floodplain forests potentially reduces organic matter available to floodplain wetlands. Furthermore, on rivers regulated to provide irrigation water in summer, floodplain wetlands that were previously inundated in spring, now flood in summer/autumn. In the Murray–Darling Basin, Australia, this has changed the timing of organic matter entering the aquatic phase, since leaf fall peaks in summer. Field surveys and mesocosm experiments on floodplain wetlands on the River Murray revealed faster processing rates of leaves in summer/autumn than spring, and no difference between cleared and forested wetlands. Temperature and leaf carbon : nitrogen ratio could not explain these differences, and instead, changes to leaf chemistry associated with ‘terrestrial ageing’ between peak leaf fall in summer and inundation in spring is more likely. The results indicated that the reduction of input of organic matter through riparian tree clearing and changing the timing of inundation interact to alter organic-matter standing stocks and rates of decomposition in floodplain wetlands. Restoring both natural timing of high flows and riparian vegetation might be required for recovery of these wetlands.

Additional keywords: decomposition, dissolved oxygen, Eucalyptus camaldulensis, mesocosm, restoration.


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