Forty mesocoms (1 m²) were used at the Olentangy River Wetland Research Park, Ohio State University, during 2007-2008 to investigate the effects of different hydrologic regimes on macrophyte structure. Pea gravel (10 cm depth) and commercial topsoil (20 cm) were filled into each mesocosm. Randomly twenty mesocosms were planted solely with Typha spp. and the other half was planted with a mixture of wetland plants: Schoenoplectus tabernaemontani, Juncus effusus, and Sparganium eurycarpum. The systems were all fed by water pumped from the adjacent Olentangy River with 4 different hydrologic regimes (pulsing, steady flow, high in spring/low flow in fall, low in spring/ high in fall).

Results/Conclusions /

After one year, there was a significant difference (p<0.05) in above-ground biomass with 4 different hydrologic regimes. Significantly higher (p<0.05) above-ground peak biomass was found with the Typha mesocoms (2.08±0.05 kg/m²) compared to the mixed plant mesocosms (0.90±0.27 kg/m²) while significant lower below-ground biomass was found with Typha mesocoms (1.65±0.15 kg/m²) compared to mixed plant mesocoms (3.05±0.40 kg/m²). Significantly higher organic carbon was found in the topsoil (0-8 cm) with Typha spp. (4.2 %) than with that of the mixed plants (3.6%). There was no significant difference in reduction of NO₃+NO₂ concentrations between the Typha and mixed plant mesocosms with 83% and 81% reduction respectively. There was a significant difference in reduction of total P concentrations between Typha and mixed plant mesocoms.