INFLUENCE OF COASTAL PROCESSES ON HIGH FECAL COLIFORM COUNTS IN THE MISSISSIPPI SOUND

Microbial source tracking efforts have historically focused on the input of fecal bacteria from sources such as storm drains, sewers, and runoff. Fecal coliform levels in the Mississippi Sound have been analyzed and compared to physical factors in an attempt to characterize possible non-point sources of pollution. Results from this study show that a primary factor in elevated levels of fecal coliforms is a change in wind direction. The passage of warm and cold fronts through the northern Gulf of Mexico causes numerous 90-180° shifts in wind directions over a period of 6-8 days. Commonly, a rise in fecal coliform counts is observed at coastal monitoring stations after an abrupt shift in wind direction and wind speed. When these trends of increased fecal coliform levels occur prior to rainfall, it is inferred that the sediment may be a source of the fecal coliform bacteria observed in the water column. The changes in wind direction and velocity may induce more energetic conditions at the shoreline (e.g. increased wave heights, and nearshore current velocities). Fecal Coliform counts collected from 5 monitoring stations along the Harrison County, Mississippi coast during 2002-2003 have been compared with wind, wave and current records from within the Mississippi Sound. The occurrence of high fecal coliform counts at multiple stations can be correlated with higher energy events in the Sound. Statistically, there is a correlation between wind direction and high bacterial counts, and higher counts are most likely to occur when the winds are out of the west or southwest at most stations.