How the seagrass Posidonia oceanica flowering will benefit from climate change.

This study aimed at identifying the importance of the thermal framework preceding Posidonia oceanica flowering induction (autumn before the flowering year) and anthesis (summer of the flowering year). In 53 locations of Sardinia (Italy), 35 vertical shoots were collected in 2001, 2020 and 2023 and analyzed through lepidochronology, detecting past flowering events from 1991 to 2022. Flowering probability was positively correlated with autumn SST range and MHWs, stressing the importance of the temperature in the year preceding the flowering. Summer SST mean and Marine Cold Spell duration (the latter emerged as a novel outcome) also positively influenced flowering. A negative association was highlighted with the summer SST range. As the occurrence of MHWs will increase, and the SST range will also increase in the autumn and decrease in the summer, P. oceanica might benefit through a higher flowering frequency, leading to a greater resilience to disturbances due to higher genetic variation.