Benthic distribution of sewage sludge indicated by Clostridium perfringens at a deep-ocean dump site

Clostridium perfringens in sediment samples collected at the Deep Water Municipal Sewage Sludge Disposal Site (also called the 106-Mile Site), off the coast of New Jersey, was enumerated. The counts of C. perfringens found in sediment samples collected within and to the southwest of the 106-Mile Site were significantly elevated (P < 0.01) compared with counts of samples from reference stations of similar depth (2,400 to 2,700 m), topography, and distance from the continental shelf, indicating that the benthic environment was contaminated by sewage dumping at this site. Low counts of C. perfringens in sediment samples collected at stations between the base of the continental shelf and the 106-Mile Site indicated that coastal runoff was not a significant source of contamination. Elevated counts were observed for samples up to 92 km to the southwest, whereas low counts were obtained for samples from stations to the east of the 106-Mile Site. This distribution is consistent with previous model predictions of sludge deposition. In areas heavily impacted by sludge dumping, C. perfringens counts were generally highest in the top 1 cm of sediment and exceeded 9,000 CFU g (dry weight) of sediment^-1. The patterns of C. perfringens dispersal observed in this study have proved useful for selection of heavily impacted areas and control stations for further ecological evaluation by a multidisciplinary research team.