Hydrology has long been considered the main driver of fish communities. The combined influences of hydrology and geomorphology on community dynamics has received less attention, particularly in relation to these interactions at multiple spatial and temporal scales. The studies that tackle the relationship between ecosystem components, and both hydrology and geomorphology, have conflicting views about which specific hydro-geomorphic features are key to producing the habitat mosaic that exists in riverine landscape and how these features drive ecosystem responses.
Several hydrogeomorphic variables representing two spatial (10s m to 10s km) and two temporal (inter-annual to decadal) scales have been identified as the main contributors to the heterogeneous character of the Upper Mississippi River-floodplain. This study aims to test if these same variables explain variation in fish community structure among eighteen backwater and island lake habitats representing a gradient of hydrological connectivity and ecosystem size.
Since riverine landscapes are hierarchical in the way they function and most ecological processes are scale dependent, we hypothesize that larger scale features such as long-term hydrology variables (e.g. decadal connectivity) and landscape-scale characteristics (e.g. position in the landscape) will influence variation in higher levels of ecological organisation such as species persistence. Whereas smaller scale features such a short-term connectivity (e.g. duration of a connection event) and patch-scale characteristics (e.g. water depth) will influence lower levels of ecological organisation such as community structure and population size-class distribution in these habitats.