Selective responses of benthic foraminifera to thermal pollution

• Foraminiferal responses to heat stress were studied in a thermally-polluted site.
• Abundances decreased corresponded to 30 °C, and 35 °C thresholds.
• The diatom bearing species P. calcariformata, is the most thermally tolerant.
• Excess warming will impair future expansion of Lessepsian and local species.

Persistent thermohaline pollution at a site along the northern coast of Israel, due to power and desalination plants, is used as a natural laboratory to evaluate the effects of rising temperature and salinity levels on benthic foraminifera living in shallow hard-bottom habitats. Biomonitoring of the disturbed area and a control station shows that elevated temperature is a more significant stressor compared to salinity, thus causing a decrease in abundance and richness.Critical temperature thresholds were observed at 30 and 35 °C, the latter representing the most thermally tolerant species in the studied area Pararotalia calcariformata, which is the only symbiont-bearing species observed within the core of the heated area.Common species of the shallow hard-bottom habitats including several Lessepsian invaders are almost absent in the most exposed site indicating that excess warming will likely impede the survival of these species that currently benefit from the ongoing warming of the Eastern Mediterranean.