305 Aquatic Botany,40 (1991) 305-320 ElsevierScience Publishers B. Y., Amsterdam Alternative criteria for assessing nutrient limitation of a wetland macrophyte I Peltandra virginica (L.) Kunth) Ij Randolph M. Chambers'and James W. Fourqurean Department of EnvirQnmental Sciences, University of Virginia, Charlottesville, VA 22903, USA (Accepted for publication 7 February 1991 ) ABSTRACT Chambers, R.M. and Fourqurean, J. W., 1991. Alternativecriteria for assessing nutrient limitation of a wetland macrophyte (Peltandra virginica (L.) Kunth). Aquat. Bot., 40: 305-320. Various nutrient incorporation and plant production parameters were measured to assess their rel- ative usefulness in determining possible nutrient limitation of the wetland plant Peltandra virginica (L.) Kunth. From four stations located along a transect in a tidal freshwater marsh, we documented spatial differences in peak standing biomass of plants. Plant biomass was positively correlated with porewater concentrations of both ammonium and phosphate, but not with sediment concentrations of total nitrogen and phosphorus. Tissue nitrogen and phosphorus concentrations decreased signifi- cantly over the growing season,but there were no differences among plants from the four stations, and correlations between plant biomass and ratios of carbon to nitrogen and carbon to phosphorus were weak. Because in situ fertilization of plants had no effect on either peak biomass or tissue con- centrations of nitrogen and phosphorus, growth of Peltandra was probably not nutrient limited. Other criteria did predict nitrogen or nitrogen and phosphorus limitation, however, demonstrating that ap- plication of parameters used by ecologists to support contentions of nutrient limitation can yield con- flicting results. Assessment of nutrient limitation of primary producers may be an ambiguous and unnecessarytask in some environments where these criteria are utilized. INTRODUCTION In recent reviews, Howartt (1988) and Smith (1984) discuss the ambigu- ities associatedwith defining and identifying nutrient limitation in aquatic ecosystems. They point out that research approaches to questions of nutrient limitation are often system-specific, e.g.techniques for documenting limita- tion in phytoplankton and vascularplants are quite different. Partly because of Redfield's (1958) pioneering work with marine phytoplankton, however, many of the techniques for estimating nutrient limitation have been devel- IPresent address:Tiburon Center for Environmental Studies, SanFranciscoState University, Box 855, Tiburon, CA 94920, USA. 0304-3770/91/$03.50 @ 1991 ElsevierScience Publishers B.V.