Impact of a ship passage on bacteria levels and suspended sediment characteristics in the Buffalo River, New York

Ship traffic in freshwater rivers may impact water quality by resuspending contaminated bottom sediment. Water samples were analyzed from two different depths at three sites across a transect of the Buffalo River, NY, before and after passage of a lake-going ship. Samples from all sites were analyzed for fecal coliform (FC), heterotrophic plate count (HPC), and total suspended solids (TSS). The levels of all test parameters increased immediately after the ship passed with the largest increases observed at mid-channel sites. Epifluorescent direct counts of mid-channel samples showed that the bacteria in the water column increased significantly (p < 0.001) at both 1 and 4 m below the surface and were positively correlated with TSS (r = 0.84). Particle size distribution in the upper water column was determined by automated image analysis. The median particle size class, by volume, before and after the ship passed was 48.9–56.6 μm and 366.5–391 μm, respectively. A few large flocculated particles accounted for most of the volume of the resuspended sediment. Resuspension of flocculated, bacteria-laden particles affects bacterial transport dynamics in riverine systems. The characteristics of flocculated sediments in suspension therefore should be considered in water quality modeling.