Effects of oil spill dispersants and drilling fluids on substrate specificity of marine bacteria

The effects of oil spill dispersants and drilling fluids on the sizes of populations of specific heterotroph subgroups of marine bacteria were monitored in this study. The bacteria were isolated from drill cuttings recovered from Agbara — an offshore oilfield located some 100 nautical miles off the Atlantic coast of Nigeria. Numbers of cellulolytic, proteolytic, starch-hydrolysing and lipolytic bacteria in the drill cuttings were monitored for 28 days in the presence of oil spill dispersants and drilling fluids. The percentages of these bacterial subgroups within the total heterotrophic population enumerated on tryptic soy agar (10% with 3% NaCl) fluctuated between 3.0 and 17.0%, 0.0 and 27.0%, 4.0 and 25.0% and 3.0 and 18.0% for cellulolytic, proteolytic, starch-hydrolysing and lipolytic bacteria respectively. These results indicate that oil spill dispersants and drilling fluids affect the ability of marine bacteria to metabolize these substrates in the environment.