Possible Use of Rna:Dna Ratio for Detecting Oil Induced Disturbance: A Field Report

The effects of oil contamination on the metabolic state of suspended participate and sedimented organic matter were investigated through the analysis of the RNA:DNA ratio on samples collected from January 1991 to January 1992 in the Ligurian Sea (northwestern Mediterranean). the ratio of RNA to DNA appeared to be highly sensitive to hydrocarbon stress since the oil disturbance resulted in an evident decline in the RNA:DNA ratio relative to the pre-pollution conditions. Such a pattern was unusual since it occurred in a period when we would expect a seasonal increase in bacterial activity. Differences are seen when comparing the temporal trend of DNA in suspended particulates and in sediments. However, the effects of oil on the RNA:DNA ratio were similar. Oiled samples showed a RNA:DNA ratio lower than 1 whereas RNA concentrations exceeded DNA content in undisturbed samples. Bacterial DNA accounted for a significant fraction (average 26%) of total DNA in sediments. It is likely that changes in RNA:DNA ratio in oiled sediments are due to the disturbance of bacterial communities. Consistent with the meiofaunal response to oil contamination, the hydrocarbons had only temporary and limited effects and RNA:DNA values recovered to pre-pollution conditions after a few weeks. the possible use of the RNA:DNA ratio in pollution monitoring is discussed.