Tidal creek systems represent the main link between watersheds and coastal waters on barrier islands. The water quality of tidal creek systems is impacted by land-based activities. Due to high rainfall amount, drainage ditches and their maintenance are used to protect households and roads from excess surface water. This study addressed the effects of drainage ditch excavation on biological contamination of intertidal Oakdale Creek (Sapelo Island, GA) that occurred between March and August of 2014. Three stations were tested; these were located in the headwater, mid-stream, and the creek mouth. Bacterial community structure along with the occurrence and abundance of pathogens (Salmonella spp., Shigella spp., E. coli O157:H7), fecal indicators (Enterococcus spp., E. coli), virulence genes (VGs- eaeA, Shig 1B, Sal invA, StxI), and a wide array of tetracycline resistance genes (TRGs) were monitored before, during, and after excavation. Bacterial composition exhibited a high degree of spatial diversity along the creek. Highest temporal shifts in community composition were detected in the water column and sediment of headwater, and coincided with the dredging schedule. Incidence of TRGs, VGs, and Pathogens and their concentrations substantially increased during and after the dredging, while abundance of Enterococci spp. and E. coli incidence and abundances were to a lesser extent elevated by the dredging. We concluded that while dredging is necessary for adequate drainage, it is a possible threat to public health while being performed. We propose that different approaches for storing excavated material should be explored to limit contamination of downstream systems.
