ESTIMATION OF THE LENGTH AND SLANT OF THE BURROW USING ULTRASOUND

There have been attempts to assess the effects on marine ecosystems of noise and other environmental pollution caused by marine development, as well as short- and long-term changes in the marine environment caused by climate change. However, the ecosystems in seafloor sediments are still unknown compared to those in the sea or on the seafloor surface because they are buried underground, making measurement difficult, time-consuming, and expensive. There are many benthic organisms under the seafloor. Many of these benthic organisms play an important role in the material cycle in the ocean, as they act as lower-order consumers and decomposers. Some benthic organisms form burrows on 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 morphol-ogy of benthic organisms can be valid for marine environment conservation. Several methods already exist that can provide information on 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, we propose a method to estimate the morphology of the burrow interior, such as the total length and slope, by transmitting broadband ultrasonic waves into the burrow and measuring the reflected waves. By using this method, it is expected to enable quick and non-destructive 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 we could estimate the inclination near the burrow opening on the order of 4° and measure the length of the actual burrow up to 18 cm.