Impacts of heavy metals, polyaromatic hydrocarbons, and pesticides on freeze tolerance of the earthworm Dendrobaena octaedra.

Previous studies have shown that the interactions between chemicals and climatic stressors can lead to synergistically increased mortality. In the present study, we investigated the effect of seven common environmental contaminants on survival at -6 and 15°C as well as on reproduction at 15°C in the earthworm Dendrobaena octaedra. Three classes of chemicals were considered: Heavy metals (nickel, lead, and mercury), polycyclic aromatic hydrocarbons (pyrene and phenanthrene), and pesticides (abamectin and carbendazim). Phenanthrene interacted antagonistically with freezing temperatures, whereas no interaction was observed with any of the tested pesticides. Two of the three tested metals (nickel and mercury) reduced the freeze tolerance synergistically (mercury was especially potent). This suggests that traditional laboratory studies, in which organisms are exposed to increasing concentrations of a single compound under otherwise optimal conditions, may underestimate the toxicity of some metals to field populations living in cold areas.