River sediments from industrial pollutant and pesticidecontaminated sites were examined with GeoChip 2.0 and the results indicated that contaminant level was not a major driver in these systems (Taş et al., 2009) . Instead, C/N ratio, depth, total Kjeldahl N, and location were the strongest drivers in determining the community structure. Most of the reductive dehalogenation genes detected were from Dehalococcoides spp., suggesting that this microorganism may play an important role in contaminant degradation in this system.