Water requirements of biota, geomorphology and climate change in the Macquarie Marshes
The Macquarie Marshes, on the lower reaches of the Macquarie River, are the largest and one of the most ecologically significant f loodplain wetland systems in the Murray-Darling Basin of south-east Australia. All wetlands, such as the Macquarie Marshes, rely on the supply of water for their long-term survival (Mitsch and Gosselink 2000) and distinct f lood events provide inundation which maintains their ecological character. In accordance with the f lood pulse concept (Junk et al. 1989), f looding is the 'principal driving force responsible for the existence, productivity and interactions of the major biota' (Junk et al. 1989, p. 110) in most f loodplain wetlands. Although the f lood pulse concept theoretically does not apply to river systems with highly variable f low regimes, Walker et al. (1995) proposed that biota in variable environments and habitats develop strategies such as opportunism and f lexibility as adaptations to f low variability. They suggest that the f lood pulse concept may apply to f loodplains with variable f low regimes, such as the Macquarie Marshes. To adequately account for the ecological role of f looding on f loodplain biota, Junk et al. (1989, p. 112) claimed that 'the resulting physicochemical environment causes the biota to respond by morphological, anatomical, physiological, phenological, and/or ethological adaptations, and produce characteristic community structures' in f loodplain wetlands. Thus, ecosystems such as those in the Macquarie Marshes are likely to be both shaped and sustained by f loodwaters from upstream, since these f lows inf luence the wetland environments within the system.