Response of microbial populations in arctic tundra soils to crude oil

Experimental crude oil spillages of 5 and 12 litre/m2 were established on the four major topographically distinguished soils of Arctic coastal polygonized tundra. The response of microbial populations to contaminating oil was found to depend on soil type and depth. Increases in numbers of heterotrophs were initially restricted to the top 2 cm of the soils. Increase in oil-degrading populations were found in oil-treated soils. Increases in microbial populations in subsurface soils paralleled downward migration of the oil. Some of the observed population increases probably resulted from input of plant residues and products from oil biodegradation.