Detection and mapping of Posidonia oceanica dead matte by high-resolution acoustic imaging

A high-resolution echosounder was used to acquire seismo-acoustic records of P. oceanica dead matte patches in the Gulf of Palermo. Seismo-acoustic profiling enabled detection of dead matte structures that are invisible to visual inspection, being hidden by variable layers of sandy sediment. The thickness of the dead matte measured reaches a maximum of 2.2 m. The mean volume of the matte per unit area of seabed surface (MEIx) varies from 0.2 to 2.2 m3/m2, with an average value of 1.6 m3/m2 and a total volume estimated at 73,000 m3. From literature data and from the volume of dead matte calculated in the present work we estimated that total carbon accumulated in the matte is about 2,484 tons. Seismo-acoustic technologies proves to be a powerful, non-destructive method to measure the thickness, extension, volume of dead matte and its potential carbon content.