Situated in Australia’s arid and semi-arid regions, Great Artesian Basin (GAB) discharge springs contain high biodiversity and many endemic species and are thought to provide the only permanent wetted refugia for the persistence of aquatic species. In contrast, springs in the recharge areas of GAB aquifers, which do not often contain endemic species are thought to be affected by the local climate conditions and do not provide permanent refugia. However, conflicting information of variable hydroperiods for both these types of springs exists including spring extinctions and activations of new springs. Information on long-term variability of springs and their biota is mostly limited to repeated sampling of individual studies and at best make comparisons within contemporary sampling records. The aim of this study was to use palaeoenvironmental information to assess and compare the millennial-scale variability in two spring wetlands: a discharge spring and a recharge spring and provide information on the likelihood of their long-term persistence.
Sediment cores were collected from spring wetlands at Byarri (Edgbaston Station, central Queensland), a discharge spring and Abercorn Station (south-east Queensland), a recharge spring. Sedimentary layers were dated and analysed using geochemistry and pollen records. Analyses indicate variable wetland and landscape conditions over the 43,000 year and 49,000 year sedimentary records and include likely anthropogenic induced changes in the landscape. While changes occurred at Byarri there is no record of a disruption in sediment accumulation, however, at Abercorn there is a distinct hiatus which is likely associated with the last glacial maximum, when the climate was significantly drier. These differences in available wetted habitat throughout sediment development in both springs corroborates that GAB discharge springs likely represent a permanent wetted refugia in Australia’s drylands, while GAB recharge springs are likely to dry during climate changes.