Porewater chemistry associated with Phragmites and Spartina in a Connecticut tidal marsh

Porewater chemistry and plant height were examined along 5 short transects extending from sections of tidal marsh dominated by the common reed Phragmites australis to these dominated by Spartina alterniflora. Phragmites was found at relatively higher tidal elevations along 4 of 5 transects; along all transects, Phragmites was growing and flowering throughout a porewater salinity range from 12 to 30 ppt. Dissolved inorganic phosphorus concentrations varied from 0 to >35 mu M in both Spartina and Phragmites sections of marsh, but ammonium concentrations averaged >40 mu M in zones dominated by Spartina and <10 mu M in zone's dominated by Phragmites. Phragmites shoots were shorter in marsh soils where sulfide concentrations were >400 mu M, perhaps due to sulfide inhibition of nitrogen uptake for growth. The persistence of Phragmites at field conditions of high salinity and elevated sulfide concentrations suggests that hydrologic management may be insufficient to eradicate Phragmites in tidal wetlands.