Salinity Tolerance and Brackish Habitat Utilization in the Common Australian Frog Crinia signifera

Ecosystem disturbance through urbanization and agriculture, coupled with anthropogenic climate change, poses a pervasive threat to ecosystem health. Such landscape disturbance can manifest as salinization, particularly in Australia. Increasing salinization of both soils and waterways has the potential to render habitats unsuitable for amphibians. However, some species exist naturally in brackish and saline habitats, which suggests the capacity to adapt to salinization. To assess this adaptability in amphibians, we examined current brackish habitat utilization by a common Australian Froglet, Crinia signifera, and determined the tolerance of eggs and tadpoles of this species to acute and chronic exposure to brackish water. Crinia signifera lay eggs in brackish water and, through laboratory experiments, we determined that short-term survival in water up to 7.5 parts per thousand (ppt) salinity is possible but may vary among populations. Chronic exposure experiments demonstrated that C. signifera can successfully complete larval development to metamorphosis in brackish water (up to 5.0 ppt). Data presented here, together with previously published reports of salinity tolerance in other Australian frog species, collectively demonstrate a capacity for adaptation to landscape salinization. This has probably been mediated by an evolutionary history in the saline landscapes so common in Australia.