We studied the independent and interactive effects of snail grazing and nutrient addition on the productivity and composition of the benthic algal community in a boreal marsh, Alaska.  Nutrient concentrations were manipulated in-situ with open-ended cylinder enclosures embedded into marsh sediments. Two grazing treatments, caged and un-caged, were nested inside each of three enclosure types; a combination of Nitrogen, Phosphorous, and Silica (NPSi), control, and ambient with four replicates each. We added NPSi to treatment enclosures every four days for 24 days. Caged treatments allowed for benthic algal colonization on natural and artificial substrates in the absence of grazing pressure.  Grazing snails (Lymnaea) were added to each enclosure to simulate natural abundances.  Increased nutrients raised chlorophyll a levels and favored the growth of filamentous green algae (Mougeotia), and coccoid blue-green algae (Chroococcus and Gleocapsa). Natural conditions favored chrysophyte growth (Euglena and Phacus). Intensive grazing reduced total algal abundance, and increased the relative abundance of small blue-green coccoid cells. Our data show that increased nutrients significantly alter benthic algal community composition and grazing significantly decreases algal biomass independent of community composition.  These independent and interacting effects are important in understanding the regulatory mechanisms of primary production in boreal wetlands.