In a previous study in White Clay Creek (WCC), a 3^rd-order southeastern Pennsylvania stream, seston and suspended particulate organic carbon concentrations exhibited a strong diel pattern; nighttime concentrations exceeded daytime concentrations by 80% and 43%, respectively.  We attributed the diel pattern of seston concentration to bioturbation by the nocturnal stream community, including crayfish, amphibians, eels, and macroinvertebrates.  In this study, we experimentally tested if bioturbation by crayfish and salamanders is a mechanism for nighttime increases in seston transport.  We measured the diel patterns of seston concentrations in WCC from June through August 2008.  Throughout the summer, nighttime seston concentrations were, on average, twice daytime concentrations with a maximum three-fold difference.  To test whether this effect was driven by bioturbation, we added crayfish and salamanders to experimental streamside flumes and measured day and night concentrations of seston exported from the flumes over six weeks.  Crayfish and salamander additions to experimental flumes did result in increases of nighttime seston concentrations by up to 75% over control flumes.  Crayfish and salamander density, size, and nocturnal activity make them ideal candidates to modify ecosystem level processes such as the downstream transport of seston and particulate organic carbon.