Climate change in edaphic systems – Impact of salinity intrusions in terrestrial invertebrates

Amongst climate change’s impacts a major concern is salinization of soils, for example due to saltwater intrusion. The aim of the present study was to investigate in a standard field soil the impacts of soil salinity increase. The purpose was to study this in two soil invertebrates that are key model ecotoxicology test-species, Enchytraeus crypticus and Folsomia candida as surrogate representatives of the soil ecosystem. The exposure followed the standard ecotoxicity OECD (Organization for Economic Cooperation and Development) test guidelines, and the assessed endpoints were survival, reproduction and size. Exposure done in LUFA 2.2 soil, spiked with 0,0.6,1,2,3,4,5,6,8 g NaCl/kg soil dry weight (DW) for E. crypticus (21 days) and 0,0.06,0.6,1,2,3,4,5,6 g NaCl/kg soil DW for F. candida (28 days). There was a similar impact for both species in terms of survival (LC₅₀=4.2 g NaCl/kg soil DW), whereas at the reproductive output level of F. candida (EC₅₀=2.1 g NaCl/kg soil DW) was more sensitive than E. crypticus (EC₅₀=2.4 g NaCl/kg soil DW). Further, size was impacted for F. candida in a monotonic dose-response curve for both adults (EC₅₀=3.5 g NaCl/kg soil DW) and juveniles (EC₅₀=2 g NaCl/kg soil DW), whereas for E. crypticus there was an increase in reproductive output at lower concentrations (0.6–1 g NaCl/kg soil DW). This increased reproduction was associated with a larger size of adults within the same concentration range. Considering the prediction from the climate models, the soil invertebrate community will be affected. As upper soils are likely to have the highest salinity increase due to evaporation, soil surface species, such as the collembolan tested here, are at higher risk. Negative population effects were occurring within salinity levels predicted by climate change models.