Review of the salinity optima of the diatomStaurosirella pinnata: implications for water reform in Australia

Abstract

Water policy reform in Australia has been driven by a requirement to increase freshwater flows to Lake Alexandrina, part of a terminal near-coastal system at the end of Australia’s longest river, the Murray. This water policy is based on the lake’s listing in 1985 under The Convention on Wetlands of International Importance as freshwater, and analysis of a limited number of diatoms from one sediment core. The analysis classified Staurosirella pinnata, the dominant diatom species, as a freshwater species. However, a review of the literature suggests S. pinnata has a very broad salinity tolerance, and a recent study in an adjacent coastal lagoon, the Coorong, indicates S. pinnata has a salinity optimum of 29 ppt. If the natural state of Lake Alexandrina is estuarine, rather than freshwater, then water policy could focus on restoring connectivity with the Southern Ocean through removal of the barrages built in the 1930s to stop salt water intrusions, rather than increased freshwater flows from the Murray River.