The impacts of bushfire ash and sediment on freshwater fauna

Date: 21, Sep, 2021
Author(s): Callum Mulvey   Rebecca Cramp   Craig Franklin   Matthew Wintour   Jarrod Cameron  

Bushfires can destroy riparian vegetation, and result in elevated water temperatures, stream bank erosion and an increase in ash-laden sediment entering the water. Addition of nutrient-rich sediment can promote algal blooms and bacterial growth, which decrease aquatic oxygen levels. There are currently no data available on how this impacts Australian freshwater fauna. We assessed how exposure to ash and sediment impacted four freshwater fish species, four crustacean species and three frog species through a series of experimental trials. Our results revealed that fish and crayfish species from cooler climates or high-altitude populations are at greater risk from bushfire-induced changes to aquatic thermal and oxygen levels than are more broadly distributed and/or lowland species. Many fish, frog and crustacean species appear highly vulnerable to the indirect effects of bushfires, but the relatively high risk is species and life stage–specific.