Global change stress on symbiont-bearing foraminifera

Abstract

Symbiont-bearing benthic foraminifera are important calcium carbonate producers and excellent model organisms for studying the global change effects. This study showed that when elevated temperatures and ocean acidification act in concert, the physiological negative effects on these organisms are stronger and even synergistic. We identified a strong photosynthetic thermal tolerance using Pulse Amplitude Modulated Fluorometry on the species Pararotalia from the Eastern Mediterranean, showing intact photosymbiosis up to 36°C. Chronic photoinhibition occurred at 42°C after one week, despite no obvious decreased survival in the species. We show that juvenile shell development in Pararotalia is highly temperature sensitive and inhibited at 20°C and 35°C. Our results point out that only some foraminiferal species seem to be well adapted to temperatures above current summer maxima. This indicates that living species have differential potential to face consequences of global warming.