ABSTRACT: Seasonal variations in above- and belowground biomass were examined over the 1994 growing season (May to October) in the 3 major plant zones of a saltmarsh located on the Bay of Fundy. Standing crop of aboveground biomass was measured over thegrowing season. Belowground samples were processed at depth intervals of 2 cm, providing high-resolution vertical profiles to a depth of 40 cm. Spartina alterniflora showed evidence of the translocation of belowground biomass to aboveground tissuein the early part of the growing season, when the rate of aboveground growth is at a maximum. Shifts in S. alterniflora organic matter storage were most dynamic in the surface 16 cm. Biomass translocation generally was not significant in the S.patens stands, where the rate of aboveground growth was consistent throughout the growing season. All seasonal changes associated with Plantago maritima biomass seem to occur before July, since no changes in above- and belowground biomass wereobserved between July and October. P. maritima contributes theleast to marsh soil organic matter.