Changes in soil moisture and temperature modify the toxicity of sodium selenite and sodium selenate for Folsomia candida (Collembola) Willem 1902

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Selenium is an essential trace element; therefore, soils are often amended with selenium fertiliser in selenium poor regions to increase the selenium consumption of the population. The amendment form can be sodium selenate and sodium selenite, depending on crop type. Climate change increases the mean temperature and also the frequency of extreme events such as drought and extreme rain. Therefore, testing the effects of different selenium forms outside the range of standard conditions can help predicting the effects of such amendments or selenium pollution. Effects of sublethal concentrations of selenite and selenate were tested on parameters of mortality, reproduction, growth, and oxidative stress parameters of Folsomia candida (Collembola) in case of different climate scenarios. The standard 20 °C and the increased 25 °C temperatures were combined with three different soil moisture conditions: drought, standard water content and increased water content.Selenite was found to be more toxic than selenate. However, the collembolan treated with selenite tolerated the increase of temperature better than those treated with selenate. The temperature increase was additive with selenium treatment in most cases. Drought was found to increase selenium toxicity in general. Also, different water contents had interactions with selenium treatments causing differences in concentration-response curves. Juvenile and egg numbers were decreased in the case of suboptimal water contents; especially drought decreased juvenile and egg numbers. No significant mortality was found under standard conditions, but mortality increased with the different climate scenarios. Results were not conclusive in the case of measurement of lipid peroxidation and glutathione status. In standard conditions, selenium did not have an effect on the juvenile number, but in combination with climate scenarios, from 1 mg Se kg−1 a decrease was found in the juvenile number. Therefore, soil selenium amendments should be carefully planned regarding the effects of changing climate, especially drought.