Characterization of soils beneath a Posidonia oceanica meadow

The study of a 475 cm core (spanning 4316 y BP) sampled in a Posidonia oceanica meadow (Portlligat Bay, NW Mediterranean) allowed us to make the first detailed description of the soil below this endemic seagrass. The sediments under P. oceanica (often referred to as mat or matte) are low density (average bulk density of 0.69 g DW cm− 3) marine soils mainly composed of siliciclastic (46%) and biogenic carbonated (46%) fine-grained sediments (particles 1 mm) and finer organic matter (3% of SOM;