Connectivity and fragmentation of flood plain-river exchanges in a semiarid, anabranching river system

The ecological integrity of flood plain-river systems is dependent upon hydrological connections between the main river channel and adjacent flood plain. These connections facilitate the exchange of carbon and nutrients and influence productivity. This paper considers carbon dynamics during phases of connection and disconnection in a large lowland river in southeast Australia. Data are presented on carbon stores in a number of anabranch channels during the disconnection phase, and the potential availability of dissolved organic carbon from these channels during the connection phase. Anabranch channels are an important physical patch type in this flood plain-river system, containing significant quantities of various carbon sources. During flooding these channels are potentially important sources of dissolved organic carbon for the main river channel. However, water resource development has reduced this potential supply of carbon by reducing hydrological connectivity between the anabranches and the main river channel. These changes have implications for the transfer of energy through the food web and hence also for the functioning of the ecosystem as a whole.