Paper No. JAWRA-08-0015-P of the Journal of the American Water Resources Association (JAWRA). Discussions are open until six months from print publication.
Ecosystem Consequences of Contrasting Flow Regimes in an Urban Effects Stream Mesocosm Study1
Version of Record online: 1 JUN 2009
© 2009 American Water Resources Association. No claim to original U.S. government works
JAWRA Journal of the American Water Resources Association
Volume 45, Issue 4, pages 907–927, August 2009
How to Cite
Taulbee, W. K., Nietch, C. T., Brown, D., Ramakrishnan, B. and Tompkins, M. J. (2009), Ecosystem Consequences of Contrasting Flow Regimes in an Urban Effects Stream Mesocosm Study. JAWRA Journal of the American Water Resources Association, 45: 907–927. doi: 10.1111/j.1752-1688.2009.00336.x
- Issue online: 29 JUL 2009
- Version of Record online: 1 JUN 2009
- Received January 17, 2008; accepted February 10, 2009.
- stormwater management;
- sediment transport;
- aquatic ecology;
Abstract: A stream mesocosm experiment was conducted to study the ecosystem-wide effects of two replicated flow hydrograph treatments programmed in an attempt to compare a simulated predevelopment condition to the theoretical changes that new development brings, while accounting for engineering design criteria for urban stormwater management. Accordingly, the treatments (three replicates each) differed in base flow between events and in the rise to, fall from, and duration of peak flow during simulated storm hydrographs, which were triggered by real rain events occurring outside over a 96-day period from summer to fall, 2005. Incident irradiance, initial substrate quality, and water quality were similar between treatments. Sampling was designed to study the interactions among the treatment flow dynamics, sediment transport processes, streambed nutrients, and biotic structure and function. What appeared most important to the overall structure and function of the mesocosm ecosystems beyond those changes resulting from natural seasonality were (1) the initial mass of fines that infiltrated into the gravel bed, which had a persistent effect on nitrogen biogeochemistry and (2) the subsequent fine sediment accumulation rate, which was unexpectedly similar between treatments, and affected the structure of the macroinvertebrate community equally as the experiment progressed. Invertebrate taxa preferring soft beds dominated when the gravel was comprised of 5-10% fines. The dominant invertebrate algal grazer had vacated the channels when fines exceeded 15%, but this effect could not be separated from what appeared to be a seasonal decline in insect densities over the course of the study. Neither hydrograph treatment allowed for scour or other potential for flushing of fines. This demonstrated the potential importance of interactions between hydrology and fine sediment loading dynamics on stream ecosystems in the absence of flows that would act to mobilize gravel beds.