A laboratory experiment was conducted to determine the effect of tubificid worms on the flux of zinc into lake sediments. Forty-six cores of Lake Erie sediment, with and without (control) tubificid worm populations, were exposed to aquarium water with a zinc concentration of about 5 mg l-' for 139 days. Pore water and exchangeable particulate zinc concentrations in the top 12 cm of sediment were periodically determined in pairs of cores -one with worms and one without worms -at 1 cm depth increments. After 139 days, pore water zinc concentrations in sediments with and without worms were nearly identical in the O-l cm interval (4.1 and 4.3 mg I-' respectively), but were significantly greater in the sediments with worms in the l-2 cm (4.4 vs. 0.3 mg '-') and the 2-3 cm (1.3 vs. 0.3 mg l-') intervals. Exchangeable particulate zinc concentrations in the O-l, 1-2, and 2-3 cm intervals in sediments with worms were 612.3, 750.7, and 191.5 pg g-' dry sediment respectively, whereas in sediments without worms, concentrations were 375.4, 5.9, and 3.2 pg g-' dry sediment. The increased flux of zinc into tubificid-inhabited sediments was caused by the 'conveyor belt' feeding activity of the worms, which continuously exposed sedimentary particles to the overlying water. Movement of zinc into sediments with worms was dominated by adsorption and by particle movement, whereas movement of zinc into control sediments was by adsorption at the sediment-water interface and diffusion. The increased concentration of zinc in tubificid-inhabited sediments has important implications with respect to the trophic transfer of zinc through the aquatic food chain.