Seagrasses represent highly productive coastal ecosystems, sustaining biodiversity and ecosystem services. In the Mediterranean, the physiology, abundance and distribution of the endemic Posidonia oceanica have been severely impacted by global warming. In this context, most research efforts have been devoted to the above-ground compartment, while little attention has been paid to the role of the below-ground compartment in regulating plant response to warming.

Since Summer 2024, we have assessed how temperature fluctuations in the below-ground compartment track those in the water column, through the deployment of temperature loggers at the canopy level and at different depths within the P. oceanica matte (-30cm, -10cm, and surface) at four locations along the Italian coast. Samples of P. oceanica roots and sediment have been collected seasonally to investigate how temperature fluctuations are associated with changes in microbial communities of the rhizosphere.

Preliminary findings suggest that the P. oceanica matte acts as a buffer, maintaining lower temperatures compared to those at the canopy level in summer and slowing sediment cooling during winter. Analyses of microbial communities associated with roots and sediments are currently in progress and will provide further insight into how fluctuations in the thermal profile are coupled with below-ground processes.

Exploring how below-ground processes vary seasonally and regulate the response of P. oceanica to warming will provide key information for the conservation and restoration of P. oceanica under future climate scenarios.

This study is part of the project BORIS (P2022R739J; CUP F53D23008230001) funded by the PRIN PNRR 2022 program.