Phytoplankton dynamics across the Ordovician/Silurian boundary at low palaeolatitudes: Correlations with carbon isotopic and glacial events

► O/S boundary phytoplankton and carbon isotope events on Anticosti are compared. ► Acritarchs display a turn-over during the early Hirnantian when D13C begins to rise. ► They display a crisis during the late Hirnantian when D13C are maximal. ► The phytoplanktonic events correlate with the development of ice-sheets on Gondwana. ► Similar phytoplankton events are recorded on Gondwana.