Annual Sedimentation Rates and Role of the Resuspension Processes Along a Vertical Cliff (Ligurian Sea, Italy)
Keywords:Sediment trap, cliff erosion, coastal sediments, suspended matter.
The annual sedimentation rates along a Portofino Promontory (Ligurian Sea, Mediterranean) cliff were studied using small sediment traps fixed directly to the rocks at 15, 20 and 25 m depth.
Monthly comparisons were made of organic and inorganic matter originating from biological production and cliff erosion in the upper water levels, with suspended matter collected in the water column close to the bottom. The highest quantity of coarse matter, related to the rainfall, was collected in the top trap. Fine sediments were due to the local sea conditions, i.e., wave suspension, and increased from the shallow to the deepest trap. This suggests that resuspension of fine sediments from the sea floor may represent an important fraction of settling matter at lower levels of the submerged coastal cliff. TOM and TSM in the water column are well correlated both at the interface and 1 m above sea floor but not with the amounts of sedimented material. Their annual trends reflect rainfall values, suggesting an influence of the terrigenous outflows.