Effects of flow alteration on the aquatic macrophyte Podostemum ceratophyllum (riverweed)
Pahl, Jennifer Plourde
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A survey of Podostemum ceratophyllum Michx. biomass and recovery rates was conducted in the Middle Oconee River, Athens, GA over a one-year time period under altered hydrology and severe drought. Biomass was found to be an order of magnitude lower than reported by previous studies conducted in non-drought years. An information-theoretic (AIC) modeling approach found variation in biomass within the study site to be related in part to variation in duration of low flow events. Recovery rates in the Middle Oconee River as well as Hunnicutt Creek, a tributary, were similar among sites and under varying hydrologic regimes. Re-colonization from vegetative growth seemed most prominent, and little support was found for seed dispersal as a major mechanism or recovery. Regionally, P. ceratophyllum range is likely expansive, and the impact of hydrologic alteration may be equally as widespread. Future monitoring could be accomplished through existing programs, focusing in basins where P. ceratophyllum is present and flow modification is prevalent.