Benthic foraminifera from the Bottsand coastal lagoon, western Baltic Sea, have been monitored annually since 2003 and accompanied by hydrographic measurements since 2012. Elphidium incertum, a stenohaline species of the Baltic deep water fauna, colonised the lagoon in 2016, most likely during a period of salinities > 19 units and average temperatures of 18 °C in early autumn. The high salinities probably triggered their germination from a propagule bank in the lagoonal bottom sediment.