A freeze‐dried autumn leaf leachate of maple (Acer saccharum) was prepared and its decomposition in hard water (⋍90 mg Ca liter‒1 and in hard water overlying freshly collected stream sediments was examined. In water alone there was very little change in the leachate levels measured as “dissolved” organic carbon (DOC); in water over sediments the leachate level was reduced to 15% of the initial level in 1 day. Rates of leachate removal during the first 9 h from water over sediments in July and October 1974 were not significantly different. Also, there was no increase in the rate of leachate removal after repeated additions of leachate. A Tyndalization sterilization technique was used to estimate the extent of removal of leachate by the sediment microflora. It appeared that at least 40% and possibly as much as 100% of the removal was a biotic process.