Estimation of seafloor burrow length and inclination using underwater ultrasound

There are many benthic organisms on the seafloor. Then, Some benthic organisms form burrows beneath the seafloor. These burrows have a considerable influence on the surrounding environment providing shelter for symbionts other than the main organisms and promoting water circulation in seafloor sediments. Therefore, the investigation of the burrow morphology of benthic organisms can be valid for marine environment conservation. Several methods already exist that can estimate the burrow shape and the organisms within the burrows. However, there is a need for a method suitable for screening surveys to measure many burrows. In this study, a novel method to estimate the morphology of the burrow interior, such as the total length and slope, using underwater ultrasound was proposed. By using this method, it is expected to enable quick and nondestructive measurement of the internal conditions of a burrow. This paper discusses the feasibility of using the proposed method to estimate the length and inclination of the burrow based on the results of laboratory experiments and field surveys. It was confirmed that the inclination angle and the length of the actual burrow can be accurately estimated on the order of 4 deg. and up to 18 cm, respectively.