A frontal system of lower Delaware Bay was investigated to illustrate the role that such tidal fronts can have in concentrating trace metals and serving as a means for introducing trace metals into the trophic hierarchy of estuaries. This frontal system typically develops on ebb tide and can extend at least 32 km parallel to the central axis of Delaware Bay. In relation to samples collected on either side of the front, chlorophyll a concentrations and concentrations of selected trace metals in zooplankton, particulates, and the dissolved fraction were significantly higher in samples collected at the front. Seasonally, concentrations of cadmium and copper in all fractions were highest during the summer or fall. Differences in taxonomic composition of zooplankton assemblages, as well as differences in total number of organisms across the front, suggested advective transport by convergent water masses.