PARENT SESSION
Contributed Oral Session 164: Wetland Chemistry
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

Validating a full-scale wetland experiment with mesocoms.

Zhang, Li¹, Mitsch, William^*,1, ¹ The Ohio State University, Columbus, Ohio, USA

ABSTRACT- Conditions in a planting experiment in two 1-ha freshwater experimental wetlands which developed distinctly different plant cover diversities and ecosystem function in 1999 were duplicated with twenty 1-m² mesocosms to provide validation of patterns and processes of ecosystem function in the full-scale experiment. Significantly higher net above-ground primary productivity (NAPP) of macrophytes was seen in mesocosms with a monoculture of Typha (823±30 g dry wt m^-2 yr^-1) that in mesocosms with a diversity of macrophytes (636±18 g-dry wt m^-2 yr^-1), similar to the pattern seen in the full-scale 1-ha wetland study where NAPP was higher in the monoculture Typha wetland (1023± 94 g-dry wt m^-2 yr^-1) than in the diverse planted wetland (657±76 g dry wt m^-2 yr^-1). General water quality and aquatic primary productivity effects did not replicate well across scales. At the mesocosm scale, the only significant difference between diversity and monoculture systems was with conductivity, which was significantly lower in the monoculture wetland outflows. For the full-scale wetlands, dissolved oxygen, pH, and gross primary productivity in the water column were lower and conductivity (salinity) was higher in the outflow in the monoculture wetlands than in the diverse wetlands. Significantly higher soluble reactive phosphorus (SRP) reduction occurred in Typha monoculture wetlands compared to the diverse macrophyte wetlands at both scales (mesocosm and full-scale). Soluble reactive phosphorus decreased by 85% in the full-scale wetlands and by 52% in the mesocosms. There were no significant differences between monoculture and diverse wetlands at either scale for total phosphorus and nitrate-nitrogen reduction. Total phosphorus concentration decreased 32% in the full-scale wetlands and 19% in the mesocosms. Nitrate-nitrogen decreased by 79% in the full-scale wetlands and by 72% in the mesocosms. Because ecological and biochemical processes in full-scale wetlands are more representative of natural conditions, experiments at full scale provide more reality even though mesocosm studies provide better replication.

Key words: wetland, mesocoms, ecosystem function, Olentangy River Wetland Research Park