Changes in sediment oxygen demand (SOD) in 2 reference and 9 oil sands process material (OSPM) impacted wetlands were evaluated. The wetlands were constructed in 1992. SOD was measured by determining the rate of O2 depletion in in-situ test chambers placed on the sediment surface within the test pond areas. The study showed that SOD measurements conducted in 2008-2009 showed a slower rate of oxygen consumption than measurements conducted in 1993. Results suggested that sediment-associated reducing compounds were depleted. Carbon dioxide (CO2) was dominantly respired by methanogens using the carbon as a terminal electron acceptor in conjunction with hydrogen to produce methane (CH4). Gases analyzed in situ from the wetland sediments suggested that OSPM-affected sediments promote the growth of methanogenic bacteria. Samples of evolved gas, pore water, and intact sediment cores were collected at each wetland site in order to determine if significant differences in biogeochemical composition have developed. Further research is being conducted to characterize the relationship between the microbes and the sediments of the reclaimed wetlands.