INFLUENCE OF MACROPHYTES ON NITRATE REMOVAL IN WETLANDS

Efficient nitrate removal from wetlands depends on denitrification. Ma crophytes support denitrification by supplying organic carbon. Organic carbon available to denitrifying bacteria is released from plant litt er and from living macrophytes. Macrophytes offer attachment surfaces for epiphytes, also producing organic matter, and for denitrifying bac teria. Emergent macrophytes are generally more productive than submerg ed macrophytes, but submerged macrophytes have more epiphytes and offe r a larger attachment area in the water column for denitrifying bacter ia. Emergent and submerged vegetation differ in their seasonal pattern s of release of organic carbon. We conclude that a mixture of emergent and submerged macrophytes may be beneficial for nitrogen removal in w etlands with a surface-flow of nitrate-rich water. The influence of ve getation on wetland hydraulics must also be considered. A wetland desi gn with deeper parts favoring submerged macrophytes alternating, along the water few, with shallower parts covered by emergent macrophytes, may promote denitrification processes and distribution of water flow.