Seabed properties and sediment erodibility along the western Adriatic margin, Italy

During February and June of 2003, selected physical and biological sediment properties were measured at nine mud-bottom sites (11–22 m) along the western margin of the Adriatic Sea. Seabed properties were compared with shipboard measurements of sediment erodibility made at the same sites to gain insight into the physical and biological controls on sediment erodibility operating in the western Adriatic. In addition, spatial patterns of erodibility were compared with long-term records of sediment accumulation in the region to determine if patterns of erodibility were responsible for the discrepancy between sediment sources and sinks on the shelf. Results indicate that sediment erodibility along the western Adriatic Sea varied both in time and space. In the wintertime, sediment in the vicinity of the Po delta (in the northern region) was less easily eroded than to the south. In the summertime, the pattern reversed. The physical characteristics of the seabed including porosity and grain-size were important factors controlling erodibility during the winter, although in a manner opposite to expectations (i.e., higher porosity sediment was less erodible). No relationship between the physical characteristics of the seabed and erodibility was observed in the summer, when it was likely that erodibility was influenced by benthic organisms, especially microphytobenthos. Results of this study suggest long-term sediment accumulation patterns along the western Adriatic Sea are unlikely to be controlled by patterns of erodibility. However, due to several complicating factors, especially along-margin variability in wave energy, the impact of sediment erodibility on long-term patterns of accumulation remains unclear. Further studies that resolve both finer and larger-scale spatial and temporal variability in sediment erodibility and that incorporate year-to-year forcing of the coastal ocean are needed to more accurately resolve the relationship between erodibility and sediment accumulation in the western Adriatic, as well as other coastal environments.