Anthropogenic pressures have caused widespread Posidonia oceanica seagrass meadow degradation throughout the Mediterranean Sea. Although restoration initiatives have been increasingly implemented, restoration success has been assessed predominantly through structural plant descriptors (e. g., shoot density, cover, growth rates). Conversely, much less attention has been paid to the recovery of habitat functions that regulate sediment dynamics and underpin key ecosystem services, including sediment trapping, blue carbon storage and nutrient and trace element retention.

This study evaluates whether seagrass restoration recovers key habitat functions, particularly sediment trapping, carbon storage and trace element retention, by comparing natural, restored (15 years after transplantation) and degraded (dead matte) P. oceanica meadows in the Gulf of Palermo. Sediment cores were analysed for grain size, carbon and trace element concentrations, whereas sediment chronologies and accumulation rates were reconstructed using the CF:CS model based on ²¹⁰Pb profiles to evaluate how habitat degradation and restoration influence sediment accumulation and the capacity of sediments to preserve coherent environmental records.

The three habitat types showed distinct sedimentary and biogeochemical characteristics. In particular, in the restored meadow, sediment texture and accumulation rates were more similar to those of the natural meadow than to dead matte, suggesting a recovery of sediment trapping and stabilization functions. Conversely, the dead matte displayed lower sediment retention and reduced temporal resolution, suggesting diminished preservation of recent environmental signals. Moreover, despite its recent reduced sediment accumulation, it retained substantial legacy carbon stocks and trace element retention, suggesting its continued ecological importance as a long-term blue carbon reservoir and biogeochemical sink.

These results suggest that assessing the recovery of habitat functions, particularly those related to sediment dynamics, provides complementary insight into restoration success beyond those obtained from plant structural descriptors alone. Their recovery regulates sediment accumulation, carbon burial and trace element retention ultimately supporting long-term ecosystem services and environmental archives.