Petroleum hydrocarbons (PHC) are the most common type of pollutant in polar regions.  The occurrence of PHC spills has a widespread geographic distribution throughout the Canadian Arctic and Circumpolar North, as well as several reported spills at various Antarctic research stations primarily located along the coast of Antarctica.  Due to the widespread and common occurrence of PHC spills in polar regions, much effort has been put forth in the area of bioremediation in cold regions.  As the technology emerges for cleaning up these contaminated sites, new questions associated with the clean up of these sites also arises.  How clean is clean enough?  What is the most sensitive part of the ecosystem?  What biological activity should be monitored to ensure that the ecosystem is being protected?  Do the environmental properties associated with polar regions increase the sensitivity of the ecosystem?  The ecotoxicity of petroleum hydrocarbon spills in polar regions is a growing concern and thus is a focal point for soil toxicology research in our lab group.

The environmental conditions that may increase the sensitivity of polar ecosystems to contaminants include sub-zero temperatures and limited liquid water content.  In polar regions, the amount of liquid water in the soil varies dramatically with the change in soil temperature.  However, even when the soil is frozen, a small amount of liquid water remains in the soil, which allows microorganisms living in the soil to remain biologically active.  The activity of these microorganisms is important, as they supply the nutrients required for plant growth, plants in turn supplies the food for primary consumers, and primary consumers supply the food for secondary consumer.  Therefore, you can see that if there are detrimental effects to soil microorganisms, the effects could manifest themselves up the food chain.  Thus it is important to protect the very basic function and structure of the soil ecosystem. We evaluated the toxicity of PHC soil contamination at an Antarctic research station by examining the effects on microorganisms.  We found that the most sensitive indicator of soil contamination was community composition (the number of different species living in the soil), followed by soil respiration and nitrification activity.  Changes in liquid water content did not seem to affect the toxicity of PHC to the soil microorganisms but it did increase the variability of the measured parameters.

Alexis Schafer