Analysis of the interaction of acoustic waves with hard and soft corals in the near field of a source.

Abstract

Hard and soft corals exist in tropical and sub‐tropical regions usually within 25–70 m of the surface. They are invertebrates with a mouth, tentacles, nematocysts, and simple sensory organs and nervous systems. Reef‐building corals live in bottom‐attached colonies and depend on moving water for transport of nutrients and removal of waste products. The physical characteristics of their bodies that promote interaction with flowing water also enhance fluid dynamic forces. Thus in the near field of a powerful acoustic source, the instantaneous drag, lift, and acceleration forces imposed on a coral reef have the potential to cause injury. An analysis of the fluid dynamic forces generated by an air gun blast was used to estimate stresses induced in stony coral skeleton and polyp tissues as a function of colony size. The stress at which injury is expected was calculated by applying a factor of safety of 2 to available values for rupture strength of stony coral skeleton and longitudinal strength of polyp connective tissue. Results indicate that polyps in colonies with characteristic length of about 5 m are likely to be injured by an air gun blast when the peak‐to‐peak received level exceeds 260 dB re 1 μPa.