Acoustic scattering by tube-building worms (Polychaeta: Maldanidae) of the New England Mud Patch

Abstract

The acoustic effects of biological activity within shallow water ocean environments are not well understood, yet are of increasing importance in some sonar applications. These environments remain insufficiently characterized in part due to the presence of benthic organisms within and near the sediment and water-sediment interface. Among the most prevalent infauna found within muddy ocean sediments are tube-building worms (Polychaeta: Maldanidae). The presence of and bioturbation caused by these organisms can affect the acoustical properties of the ocean bottom sediment. These effects are being studied in experiments being conducted in the New England Mud Patch, on the continental shelf south of Martha’s Vinyard, MA. To begin to quantify these effects, laboratory acoustic scattering measurements of naturally collected worms and worm tubes were completed over a range of frequencies (50 kHz to 1 MHz) and incidence angles. Predictive models by Faran [J. Acoust. Soc. Am. 23, 405 (1951)] approximating the worms as elastic cylinders, and Doolittle [J. Acoust. Soc. Am. 39, 272 (1966)] approximating the worm tubes as cylindrical shells, were used to interpret the measured results. Measurements and model comparisons will be discussed along with implications relating to effective bulk sediment properties. [Work supported by ONR.]