Temporal fluctuations in the acoustic scattering from bottom-deployed objects and localized biological treatments

A field experiment was carried out to examine the time variation of scatter ing from man-made objects placed near the water-sediment interface and with in the sediment. The objects (spheres) were monitored for a period of about two months using a sonar system capable of measuring scattering levels, bo ttom bathymetry, and correlation of scattering over time. In addition, dive rs performed localized biological treatments that were also monitored over extended periods. The results of these monitoring activities are presented and related to previous studies that used the same data sets for other purp oses. One notable result is that the buried sphere becomes undetectable (by scattering level alone) within two days of deployment. The rapid changes i n the first few days after the buried sphere is introduced are quantified r elative to the rate of changes for undisturbed regions of the sediment.