Macroinvertebrate assemblages in floodplain habitats of the lower river murray, South Australia

Abstract

Macroinvertebrates were sampled in seven microhabitats (submerged woody debris, reeds, sedges, inundated grass, floating aquatic vegetation, lignum, and the unvegetated littoral) at thirteen sites representing six macrohabitats (single temporary and permanent ox-bow lakes (billabongs), fast and slow-flowing anabranches, backwaters, and the main channel) of the River Murray, and Australian lowland river. Sites were sampled in spring 1988, shortly after floodwaters had receded.Most of the 95 taxa collected were aquatic insects. Detritivores were most abundant in all macrohabitats except the temporary billabong where predators predominated. Scrapers were only abundant in the permanent billabong. The temporary billabong harboured the most species and individuals whereas slowly-flowing anabranches contained the fewest species and individuals. At the microhabitat level, most taxa and individuals occurred in stands of aquatic vegetation. The unvegetated littoral zone was the most depauperate microhabitat.Multivariate analyses illustrated the distinctiveness of the faunal assemblage found in the temporary billabong. Subsequent analyses of the permanently inundated macrohabitats indicated gradients related to current velocity and the extent to which the sites were continuous with the main river. Current velocity apparently determined assemblage composition at the macrohabitat scale whereas the structural complexity of submerged vegetation operated at the microhabitat scale.The relatively large number of taxa collected from this area emphasizes the importance of a range of macrohabitats and microhabitats to faunal diversity in a floodplain ecosystem. Although there was little faunal overlap between billabongs and the main river, billabongs probably serve as refuges for many lentic taxa that rely upon regular inundation to survive. Surveys of floodplain rivers for management purposes must include samples from aquatic habitats adjacent to the main channel because the fauna of the floodplain is potentially most threatened by regulation and alteration of the flooding regime.

An arid zone awash with diversity: patterns in the distribution of aquatic invertebrates in the Pilbara region of Western Australia

“…These variables are considered to be primary drivers of invertebrate community composition in dryland rivers (Boulton and Lloyd 1991;Timms 2001;Timms and Boulton 2001;Sheldon et al 2002;Shiel et al 2006) but their effects are difficult to separate in survey datasets such as this.…”

“…The importance of macrophytes and sediments as structural features of arid zone wetlands has not been as much of a focus as have the roles of hydrology, salinity and turbidity, but some authors have indicated their importance (Boulton and Lloyd 1991;Sheldon et al 2002). They are certainly known to influence invertebrate communities more generally (Williams and Mundie 1978;Cyr and Downing 1988;Wollheim and Lovvorn 1996).…”

Hydrological changes and ecological impacts associated with water resource development in large floodplain rivers in the Australian tropics

“…This knowledge gap is especially noticeable in comparison with Australia's southern rivers, such as those in the Murray-Darling Basin (e.g. Boulton and Lloyd, 1991;Sheldon and Walker, 1998;Kingsford, 2000;Reid and Brooks, 2000;Balcombe et al, 2006).…”

Floodplains of a regulated southern alpine river (Brenno, Switzerland): ecological assessment and conservation options

“…For example, taxon richness of aquatic invertebrates tends to be higher in floodplain water bodies than in the river channel (Ward et al, 1999b). The regulation of the discharge regime is the most severe threat for the aquatic floodplain fauna (e.g., Boulton and Lloyd, 1991;Homes et al, 1999); consequently, conservation strategies will have to focus on flow management, particularly because most channelizations are irreversible. Ecological flows can restore the hydrological connectivity between a river and its floodplain (Richter et al, 1998) but this requires a partnership between ecologists, river managers and policy makers in order to achieve economically feasible as well as ecologically meaningful solutions.…”