Little is known about invasive species impacts on nutrient cycling in tropical streams, and furthermore, how ongoing degradation of riparian vegetation mediates the influence of invaders. We examined nutrient recycling by two exotic snails (Tarebia granifera and Melanoides tuberculata) as a function of light availability in two Trinidadian streams and in light-manipulated experimental channels. We collected snail abundance, biomass, and excretion (NH4 and SRP) data to determine snail-derived nutrient remineralization per (1) area of streambed and (2) snail biomass.  Where riparian vegetation had been removed and direct sunlight reached the streambed, both species of snails were more abundant and per-area remineralization of NH4—but not SRP—was significantly greater than in closed canopy conditions.  Patterns of per-biomass NH4 excretion rates in streams were less consistent among light conditions; however, results from experimental manipulations suggest that high light availability increased epilithon C:N and decreased T. granifera biomass-specific NH4 remineralization relative to snails grazing in low light conditions.  Thus, light availability in tropical streams—and therefore riparian canopy presence—can influence both biomass- and area-specific nutrient recycling by exotic snails.  Human-mediated destruction of riparian vegetation in the tropics may therefore facilitate proliferation of aquatic invaders and augment their influence on ecosystem-scale processes.