Leslie Rieck's Graduate Exit Seminar
On Thursday, June 27th at 12 noon in Heffner Building Room 128, Leslie Rieck will present her graduate exit seminar, Associations Between Hydrogeomorphic Characteristics and Biotic Community Dynamics in Urban Streams of Columbus, Ohio, USA.
Urbanization of watersheds leads to myriad changes to streams, including modified sediment and streamflow regimes that can result in altered fluvial geomorphic processes and channel structure. These hydrogeomorphic features have been linked to community composition of aquatic biota, as well to stream ecosystem functioning although the specific mechanisms through which urban land use and subsequent hydrogeomorphic modification effects these changes remain unresolved. In 23 small urban stream reaches in the Columbus Metropolitan Area (CMA), Ohio, USA, I investigated potential linkages between urban-induced hydrogeomorphic modification and: (1) fish assemblage compositional changes over time (3-5 years); (2) fish assemblage trophic dynamics; (3) aquatic-to-terrestrial nutritional subsidies to a common riparian consumer (spiders of the family Tetragnathidae); and (4) downstream drift of larval macroinvertebrates in the water column. I found that hydrogeomorphic characteristics pertaining to the maintenance of heterogeneous and stable instream habitat (e.g., discharge magnitude, shear stress) and floodplain connectivity (e.g., sinuosity, incision ratio) were most important for multiple ecological responses: fish assemblage structure and function, aquatic-terrestrial connectivity via pulses of emergent aquatic insects into the riparian zone, and the downstream transport of aquatic macroinvertebrates. My findings suggest that urban land development cascades, through hydrologic and sediment-related alterations (e.g., discharge magnitude, shear stress), to impact physical channel (geomorphic) form (e.g., sinuosity, floodplain connectivity) and, in turn, instream habitat and biotic community structure and function. An ecogeomorphic approach – such as the one I adopted here – is therefore a promising avenue toward further understanding and restoring critical physical-biologic processes (e.g., cross-ecosystem energy flows) that are key to forming and maintaining resilient urban stream ecosystems.