Clostridium perfringens in Long Island Sound sediments: An urban sedimentary record

Clostridium perfringens is a conservative tracer and an indicator of sewage -derived pollution in the marine environment. The distribution of Clostridi um perfringens spores was measured in sediments from Long Island Sound, USA , as part of a regional study designed to: (1) map the distribution of cont aminated sediments; (2) determine transport and dispersal paths; (3) identi fy the locations of sediment and contaminant focusing; and (4) constrain pr edictive models. In 1996, sediment cores were collected at 58 stations, and surface sediments were collected at 219 locations throughout the Sound. El evated concentrations of Clostridium perfringens in the sediments indicate that sewage pollution is present throughout Long Island Sound and has persi sted for more than a century. Concentrations range from undetectable amount s to 15,000 spores/g dry sediment and are above background levels in the up per 30 cm at nearly all core locations. Sediment focusing strongly impacts the accumulation of Clostridium perfringens spores. Inventories in the core s range from 28 to 70,000 spores/cm(2), and elevated concentrations can ext end to depths of 50 cm. The steep gradients in Clostridium perfringens prof iles in muddier cores contrast with concentrations that are generally const ant with depth in sandier cores. Clostridium perfringens concentrations rar ely decrease in the uppermost sediment, unlike those reported for metal con taminants. Concentrations in surface sediments are highest in the western e nd of the Sound, very low in the eastern region, and intermediate in the ce ntral part. This pattern reflects winnowing and focusing of Clostridium per fringens spores and fine-grained sediment by the hydrodynamic regime; howev er, the proximity of sewage sources to the westernmost Sound locally enhanc es the Clostridium perfringens signals.