Here today, gone tomorrow – the Levantine population of the Brown mussel Perna perna obliterated by unprecedented heatwave

The newly established population of Perna perna surveyed at four sites along the Israeli Mediterranean coast averaged between 2155 and 8022 specimens/m² in June 2021. Three sites displayed unimodal size–frequency distributions, whereas the site adjacent to Haifa port – a bimodal distribution. The population suffered catastrophic mortality following a succession of heatwaves culminating in a prolonged heatwave in August (ambient temperature 36 to 38 °C, sea surface 32 °C), with diurnal low tides occurring midday. With the projected rise in both mean temperature, and prevalence, duration, and severity of extreme high temperature events, it is likely that even if a P. perna reoccurs, it will be of brief duration.