Conservation value of variable connectivity: aquatic invertebrate assemblages of channel and floodplain habitats of a central Australian arid-zone river, Cooper Creek

Rapidly expanding water resource development in arid and semi-arid zones of Australia threatens the flow regime and ecological integrity of the few la rge dryland rivers and their immense floodplains. Efforts to manage and con serve the surface waters of these rivers are hampered by limited scientific data on the ecology of their flora and fauna and on their responses to the high natural variability of flow regime that typifies dryland rivers. Irre gular floods connect channel and floodplain wetlands to differing degrees a nd for varying periods of time but the ecological significance of this conn ectivity is poorly understood. On Cooper Creek, a large dryland river in ce ntral Australia. we explored the degree to which assemblage composition var ied with connectivity and hydrological regime. Shortly after protracted reg ional flooding, we sampled aquatic macroinvertebrate assemblages from the p rincipal microhabitats in 12 channel and floodplain wetlands. Ephemeral and temporary lakes tended to have fewer taxa than semi-permanent channel or t erminal lake habitats. Although hydrological connection had only recently b een lost for some wetlands, there was already evidence of divergence in aqu atic macroinvertebrate assemblage composition. Disruption of the natural va riability in connectivity and hydrological regime by excessive water abstra ction or river-flow regulation threatens the ecological integrity and aquat ic macroinvertebrate biodiversity of dryland rivers. Preservation of the ir regular flow regime and sporadic connectivity underpins conservation of the mosaic of floodplain wetlands that play such a crucial role in the ecosyst em functioning of rivers such as Cooper Creek. (C) 2001 Elsevier Science Lt d. All rights reserved.