An Isolated Hyposaline River Occurrence of Birsteiniolla (Foraminifera) From Western Australia, Previously Known From Central Asian Lakes and Interior Seas

A low diversity foraminiferal assemblage inhabits a hyposaline stretch of the Jerdacuttup River, which flows into Jerdacuttup Lakes near Hopetoun, south coast Western Australia, but is not connected, at least by any surface flows, to the open Southern Ocean. Among the six species of foraminifera identified is an organic-cemented agglutinated type ( Birsteiniolla gr. macrostoma ) that is morphologically like Birsteiniolla macrostoma Yankovskaya and Mikhalevich known only from Central Asian lakes and interior seas (e.g., Lake Issyk-Kul’, Caspian and Aral seas). In late 2016 sampling it was very abundant on stems of Ruppia seagrass that form meadows on the river floor but was very rare in September 2019 when the organic-cemented agglutinated Scherochorella gr. barwonensis was abundant on the seagrass. Foraminiferal distributions are patchy in the river’s muddy sediment. The calcitic rotaliine Ammonia haigi is the most abundant species and is morphologically close to Ammonia caspica from Central Asia, as is the other common calcitic rotaliine species identified here, Cribroelphidium sp. cf.  C. revetsi , which is close to Cribroelphidium caspicum from Central Asia. The other foraminiferal species are Miliammina ? sp. and Trochammina gr. inflata , both with similar morphotypes recognized globally. It is speculated that the Jerdacuttup River foraminifera were transported via water birds (probably in their digestive tracts) on the East Asian–Australasian Avian Flyway. The migration pathway may have involved local migration between the isolated Australian river systems as well as the intercontinental migration, leading to some potential genetic diversification. A three-point research strategy is outlined that may confirm this hypothesis.