Hydrological control of system characteristics of floodplain lakes

Water bodies within floodplains are strongly governed by their hydrological connectivity with the main river (Heiler et al. 1995). Connectivity is decisive for the general ecosystem characteristics and the balance between input and output of nutrients and organic carbon sources.A major determinant is the abundance of macrophytic vegetation, which is controlled by through-flow, dry-falling and scouring effects.The autochthonous primary production is strongly augmented by local terrestrial carbon sources and by the riverine transport in form of dissolved and particulate organic matter. The significance of these different sources depends on hydrology.Flood pulses represent a disturbance to pelagic communities (followed by successions) and a source of nutrients. High loads of inorganic nutrients produce conditions for prolific algal growth.High availability of allochthonous organic carbon provides the basis for a prolific bacterial secondary production. Our data emphasize that the stimulus of local aquatic primary production enhances carbon utilization by bacteria.