Breakdown rates, macroinvertebrate and bacterial colonization, and microbial respiration were measured on decaying maple (Acer saccharum) leaves at three sites along a stream-marsh continuum . Breakdown rates (-k ±SE) were 0 .0284±0.0045 d -i for leaves in a high-gradient, non-tidal stream ; 0.01 12±0 .0019 d -t for leaves at the confluence of the stream with a tidal, freshwater marsh ; and 0 .0062±0.0009 d -1 for leaves in the tidal, freshwater marsh . Breakdown rates were significantly faster (ANCOVA, F<0 .008) at the high-gradient, non-tidal stream site and at the tidal stream site than in the tidal marsh . Macroinvertebrate density on decaying leaves was low at all sites (<7 organisms g -' AFDM leaf mass) and was dominated by chironomids and amphipods . Bacterial density on decaying leaves ranged from 8 .56 x 10 1 CFU g-t AFDM leaf mass to 13 .38 x 10 1 CFU g -t AFDM . Cumulative microbial respiration, calculated as the product of mean respiration on a sampling date, days in the interval preceding the sampling date, and hours per day, accounted for 34 .3±6 .0%, 53 .0±4 .8%, and 51 .5±7 .9% of the leaf mass loss (as carbon) at these sites . Although the breakdown rate was fastest at the non-tidal stream site, significantly less leaf mass was lost through microbial respiration . Most mass loss from leaves at this site was probably due to physical processing associated with stream habitats .