The control of algal blooms in water reservoirs with cutrine - a copper-containing algicide - results in Cu accumulation in reservoir sediments. However, the impact of Cu-enrichment on mineral N availability and N cycling processes is largely unknown. To that end, a study was conducted using sediment from cutrine-treated and untreated sections of 3 central Indiana reservoirs. Total Cu (mg Cu kg-1) in cutrine-treated (70 - 425) was much greater than in untreated area (17-40). There was no correlation between Cu levels and in-situ NH4, respiration and sediment C quality (C/N, H/C ratios). Negative relationships were found between in-situ NO3 and both exchangeable and organic-bound Cu in sediment. While no effect on activity was noted at total sediment Cu < 40 mg kg-1, N2O reductase activity increased as concentrations of labile Cu increased. When sediment samples were amended with CuSO4 (50, 100, 200 mg Cu kg-1), a decline in N2O-reductase activity was recorded during the first 2 h of incubation probably corresponding to an adaptation period, but after 48 h incubation, N2O-reductase activity increased almost proportionally with the amount of Cu added. These results indicate that Cu-enrichment does not affect the capacity of sediment to denitrify but could reduce the proportion of N2O in denitrification products.