POLYNUCLEAR AROMATIC HYDROCARBON CONTAMINANTS IN OYSTERS FROM THE GULF-OF-MEXICO (1986-1990)

Polynuclear aromatic hydrocarbon (PAH) contaminant concentrations in 8 70 composite oyster samples from coastal and estuarine areas of the Gu lf of Mexico analyzed as part of National Oceanographic and Atmospheri c Administration's (NOAA's) National Status and Trends (NS&T) Mussel W atch Program exhibit a log-normal distribution. There are two major po pulations in the data. The cumulative frequency function was used to d econvolute the data distribution into two probability density function s and calculate summary statistics for each population. The first popu lation consists of sites with lower PAH concentration probably due to background contamination (i.e. stormwater runoff, atmospheric depositi on). The second population are sites with higher concentrations of PAH s associated with local point sources of PAH input (i.e. small oil spi lls, etc.). The temporal pattern for the mean concentration of the pop ulations from the Gulf of Mexico is consistent with large-scale climat ic factors such as the El Nino cycles which affect the precipitation r egime.