CHAPTER ONE 1.0 INTRODUCTION Crude oils are composed of mixtures of paraffin, alicylic and aromatic hydrocarbons. Microbial communities exposed to hydrocarbons become adapted, exhibiting selective enrichment and genetic changes resulting in increased proportions of hydrocarbon-degrading bacteria and bacterial plasmids encoding hydrocarbon catabolic genes (Leahy and Colwell, 2004). Adapted microbial communities have higher proportions of hydrocarbon degraders that can respond to the presence of hydrocarbon pollutants. The measurement of biodegradation rates under favorable laboratory conditions using 14C-labelled hexadecane has led to the estimation that as much as 0.5 – 60 g oil/m3 seawater convert to carbon dioxide, depending on temperature and mineral nutrient conditions. The principal forces limiting the biodegradation of polluting petroleum in the sea are the resistant and toxic components of oil itself, low water temperatures, scarcity of mineral nutrients ( and phosphorous), the exhaustion of dissolved oxygen and in previously unpolluted areas, the scarcity of hydrocarbon-degrading microorganisms (Atlas, 2002).Low winter temperature can limit rates of hydrocarbon biodegradation increasing resident time of oil pollutant(Bodennec et al., 2007).Bio-degradation is nature’s way of recycling wastes, or breaking down organic matter intonutrients that can be used and reused by other organisms.

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