Palaeoenvironmental support for long-term aquatic refugia in Australia’s Great Artesian Basin discharge springs

ABSTRACT

In dryland areas, wetland refugia that provide permanent wetted habitats are important for the persistence of obligate aquatic species. Situated in Australia’s arid and semiarid regions, Great Artesian Basin discharge springs contain high biodiversity and many endemic species and are believed to provide the only permanent wetted habitat. However, conflicting information indicates that hydroperiods in these springs can be variable. The aim of this study was to use palaeoenvironmental information to assess millennial-scale variability in one large spring wetland and provide an initial assessment on the long-term presence of wetted habitat. A sediment core was collected from Big Spring at Byarri (Edgbaston Station) in central Queensland, Australia, and the sedimentary layers were analysed using radiocarbon dating, geochemistry, and palynology. An age model developed on the radiocarbon dates indicated that changes in the rate of sediment deposition are likely associated with the last glacial maximum but with no disruption in the sediment accumulation, or therefore wetland development. Variable wetland and landscape conditions over ∼43 000 years are supported by the geochemistry and palynological sedimentary records, including a change from a lacustrine to palustrine wetland and more recent changes, likely due to an anthropogenic presence in the landscape. The lack of a hiatus in available wetted habitat throughout the period of sediment development corroborates that Great Artesian Basin discharge springs represent a permanent wetted refugia in Australia’s drylands.

KEYWORDS:

• aquatic refugia
• Itrax; micro X-ray fluorescence
• radiocarbon
• spring wetlands

Acknowledgements

We acknowledge Bush Heritage Australia, the property owners of Edgbaston Springs, for allowing us to work on the spring wetland; Rob Wager and Peter Unmack for supporting fieldwork; and Matthew Young for assisting with field collection of the sediment core. We also thank Giselle Pickering and Sara Clifford and 3 anonymous reviewers for their helpful comments on the manuscript. The Itrax µXRF analysis and radiocarbon dating was supported by ANSTO under portal grant AP12395.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by an ANSTO Portal Grant [Grant Number AP12395].