In the study, we describe the sedimentary dynamics in a shallow-water seagrass meadow. We examined the dynamics
of vertical sedimentation flux over a Posidonia oceanica meadow during the course of a one-year investigation. Total
sedimentary flux was monitored off the northern Latium coast (Italy) in the central Tyrrhenian Sea using sediment traps
from October 2015 to December 2016 at three stations established on bare sand, in the P. oceanica meadow, and on
a sand patch within the meadow. The traps were deployed during 11 surveys planned on the basis of the weather
conditions and seagrass growth phase. The trap content was analysed for the amount of mass trapped and grain-size
statistics, useful for describing sedimentary processes during storms. The meteorological data, P. oceanica
parameters, and sand patch evolution during the year were analysed to determine their relation to the vertical
sedimentation flux. The resuspension process dominated the shallow-water dynamics, but P. oceanica buffers the
resuspension, especially during calm sea conditions. The sedimentological tracers showed that when high energy-flow
regimes were present, the vegetation near the bottom enhanced the deposition of particles transported from adjacent
unvegetated areas. During late Summer, leaf litter deposited on the unvegetated seafloor buffered the seabed
sediment particles, preventing resuspension. We also detected the active transport of material from the sand patch to
the meadow that was dependent on the energy flow regime, showing that the vegetation plays two roles: preventing
resuspension and promoting deposition.
