LONG-TERM INVESTIGATIONS ON CHEMICAL AND MICROBIAL CHANGES OF A SLIGHTLY OIL POLLUTED BEACH1
ABSTRACT A sandy and muddy beach polluted by Arabian light crude oil in 1974 was investigated in 1974, 1975, and 1981. The shift of the hydrocarbon contamination from the sand to the mud has been determined by infrared spectroscopy and glass capillary gas chromatography. In 14 months, the mean values of the hydrocarbon content in the sandy beach declined from 203 milligrams per liter (mg/l) to 10 mg/l. However, those of the mud flat increased by 300 percent (from 37 mg/l to 108 mg/l). Six years later, the fossil fuel hydrocarbon concentration had decreased to 0.6 mg/l and 8 mg/l for the sandy and muddy beach, respectively. Nevertheless, both areas still reflect the former polluting event. This was established definitively by the trace analysis of acyclic isoprenoid alkanes (norpristane, pristane, phytane) which indicates oil contamination by detection of mature diastereoisomers. The bacteria reflect the fate of the hydrocarbons. The numbers of oil degraders rapidly increased by several orders of magnitude within the first weeks and reached maximum values well above 1011 per liter of sediment. Simultaneously, the overall ratio of oil-degrading bacteria to normal heterotrophs topped 270 percent, decreasing gradually to the normal background value within one year. The highest ratio of oil degraders was found in the sandy beach shortly after the spill and in the muddy beach after several months.