PARENT SESSION
Oral Session #33: Biodiversity and Ecosystem Function: Nutrients, soils, microbes.
Presiding: K. Brown
Tuesday, August 6. 8:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.
Effects of macrophyte diversity on denitrification in a mesocosm experiment.
Gilbert, Janice*,1, Frey, Serita1, Bouchard, Virginie1, 1 Ohio State University, Columbus, Ohio
ABSTRACT- We examined the relationship between aquatic plant (macrophyte) diversity and denitrification in mesocosms simulating an emergent marsh ecosystem. We hypothesized that a decline in macrophyte diversity would lead to a reduction in bacterial diversity resulting reduced production of nitrous oxide (N2O)reductase enzymes and a subsequent reduction in denitrification gas fluxes. Fifty-five mesocosms (417 litre tubs) with combinations of 0,1,2,3,4 or 5 macrophyte functional groups were assayed for in situ N2O gas flux using the acetylene block method, denitrifying enzyme activity, total and labile sediment organic carbon, and sediment bacterial biomass and diversity (T-RFLP). Sediment bacterial biomass was correlated (r2 = 0.65) to above- and below-ground plant biomass. Denitrification enzyme activity averaged 333±21, 357 ±3 and 921±53 mg N m-2 day-1 in mesocosms containing 0, 1-4, and all 5 functional groups, respectively. There was a significant increase in denitrifying enzyme activity per unit dissolved organic carbon in the sediment porewater across the diversity gradient. In situ N2O flux exhibited a general increase from 2.4 to 5.2 mg N m-2 day-1 in mesocosms increasing in plant diversity from 1 to 5 functional groups. Our study indicates that altering plant functional diversity affects ecosystem function (i.e. denitrification) and therefore has potentially important implications for a number of environmental issues connected to wetland mitigation and global climate change.
KEY WORDS: Biodiversity, Denitrification, Macrophytes, Wetlands