Interpretation of Biological Activity Using an Acoustic Backscatter Sensor (ABS)

Acoustics aid in the description of complex processes, such as the suspension of sand particles exposed to local hydrodynamic forces above a rippled bed (Cacchione, et al., 2008). Acoustic data can be applied to several aspects of the marine environment such as marine chemistry, biology, geology, and ecology. The acoustic data collected in this study was part of a larger, grant-funded project that focused on sediment transport and settlement preference on two offshore hardbottoms following beach renourishment along the heavily developed coast in northeastern South Carolina. Acoustic data collection was used in the larger project to describe changes in sediment concentrations offshore of Myrtle Beach, SC on the inner-shelf of Long Bay, SC (Wren et al., 2010). During certain time periods, data collected by the Acoustic Backscatter Sensor (ABS) do not appear to be correlated with wave or current data (Wren et al., 2010). Additionally, during these times the ABS indicates that there are larger particles suspended in the middle of the water column (Wren et al., 2010); however, there are no strong currents or waves to suspend sediment. These anomalies occur during fall and spring months (Wren et al., 2010). Without a driving force for sediment re-suspension, the cause of the acoustic return in the middle of the water column is unknown. The purpose of this study is to determine if the acoustic data can help identify unusual concentrations of large particles in the middle of the water column as possible biological interference