Effect of dispersed oil on heterotrophic bacterial communities in cold marine waters

Abstract

Mesocosm studies were conducted to evaluate the effect of dispersed oil on total and heterotrophic bacterial communities of under-ice seawater from the St. Lawrence Estuary. A regular survey of bacterial changes in the oil-contaminated seawater was performed during a two week period. The bacterial community structure was investigated by carrying out 27 morphological and biochemical tests on 168 isolated strains. The results show a detectable but transient response of the bacterial community to crude oil addition. While total bacterial counts were approximately constant during the experiment, dispersed oil induced an increase in heterotrophic bacterial microflora (from 10(4) to 10(5) bacteria ml(-1) after two weeks of contamination). The dispersed oil appeared to have an inhibitory effect on some components of the bacterial community. A decrease of most probable number values was observed just after addition of crude oil in the most polluted tanks and one day later in the less polluted tank. However, except for the most polluted tank, this adverse effect disappeared rapidly. While the dispersed oil induced a total disappearance of some components of the bacterial community in the most polluted tank, the structure of the bacterial community in the less polluted tank appeared relatively unchanged after 14 days of contamination.

Enhanced bacterioplankton activity after the ‘Prestige’ oil spill off Galicia, NW Spain

“…At first, abundance values were within the range observed before the spill. This result agrees with other field studies in open waters (Delille & Siron 1993) but contrasts with those reported for laboratory experiments with oil-treated microcosms, in which total number of bacteria increased significantly after contamination with water soluble hydrocarbons (Medina-Bellver et al 2005, Sargian et al 2005. Such difference could be due not only to the variable toxicity of the different hydrocarbons involved in each case study, but also to their concentrations and time of exposure for the bacterioplankton.…”

“…At the same time, hydrocarbon-degrading bacteria often increase their relative abundance in natural communities after an oil spill (Maruyama et al 2003, Bordenave et al 2004. Changes in total abundance and production of natural bacterioplankton communities in relation to oil spills, however, are rarely reported (Delille & Siron 1993, Piehler et al 2002.…”

Reciprocal Effects of Oil-contaminated Soil and Festuca (Tall fescue)

“…Previous reports show that increasing crude oil concentration decreased the microbial population of the soil (Delille and Siron 1993). On the contrary, our results showed that in the presence of high concentration of crude oil (10 and 7 %), the microbial population and oil degrading bacteria, increased in comparison with the control and lower concentrations of crude oil (1 and 3 %).…”

Risques et impacts associés à l’exploration et à l’exploitation des hydrocarbures dans le golfe du Saint-Laurent

“…Leur présence dans les eaux froides de l'estuaire du Saint-Laurent a été démontrée (Delille et Siron, 1993) et pourrait être liée aux quelque 1 900 évents naturels de méthane répertoriés par Lavoie et collab. (2010) dans l'estuaire.…”