Abstract

Microbial source tracking efforts have traditionally 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 coliform is barometric pressure and the resulting changes in wind direction. The passage of warm and cold fronts through the northern Gulf of Mexico cause excursions in barometric pressure and numerous 90°-180° shifts in wind direction over a period of 6-8 days. Commonly, a rise in fecal coliform counts is observed at the selected coastal monitoring station during, or immediately after a drop in barometric pressure and 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 increased long shore current velocities). Fecal coliform counts collected from a Mississippi Department of Environmental Quality (MDEQ) monitoring station (Station 10) along the Harrison County, Mississippi coast during October - December, 2004 have been compared with barometric pressure readings over that time interval. The occurrence of high fecal coliform counts can be qualitatively correlated with low barometric pressure. Statistically, a correlation exists between high barometric pressure and low bacterial counts. Low bacterial counts are most likely to occur (66% greater chance) when the barometric pressure exceeds 30.1 inches Hg (1019.3 mbar), with winds from a northerly direction. Analyses of fecal coliform counts in coastal waters, feeder creek waters, sewers, and coastal sediments are currently underway to determine relationships between these potential environmental sources of fecal pollution.