Synergistic interaction between 4-nonylphenol and high but not low temperatures in Dendrobaena octaedra

Studies on joint effects of toxic compounds and temperature have clearly shown that single stressor tests often underestimate the critical limits of the stressor evaluated. In the present study, the joint effects of nonylphenol (NP) and high (25–35 °C) or low (1.4 to −6.4 °C) temperatures in Dendrobaena octaedra were elucidated. The effects of these combined stresses were analyzed in a multiplicative model using an independent action model as a reference, and there was a strongly synergistic interaction between the effects of NP and high but not low temperatures. This interaction may be caused by NP disrupting membrane stability during thermal stress and/or by a depletion of protective heat shock proteins. While the survival of D. octaedra at high temperatures significantly decreased with increasing NP concentration up to 400 mg kg−1 dry soil, reproduction was significantly reduced when the earthworms were exposed to a concentration as low as 30 mg NP kg−1 dry soil.