POREWATER CHEMISTRY ASSOCIATED WITH PHRAGMITES AND SPARTINA IN A CONNECTICUT TIDAL MARSH

Porewater chemistry and plant height were examined along 5 short trans ects extending from sections of tidal marsh dominated by the common re ed Phragmites australis to these dominated by Spartina alterniflora. P hragmites 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 ino rganic phosphorus concentrations varied from 0 to >35 mu M in both Spa rtina and Phragmites sections of marsh, but ammonium concentrations av eraged >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 i nhibition of nitrogen uptake for growth. The persistence of Phragmites at field conditions of high salinity and elevated sulfide concentrati ons suggests that hydrologic management may be insufficient to eradica te Phragmites in tidal wetlands.