Development & in situ application of ultrasonic acoustic system for real-time marine harmful algal bloom’s detection

Abstract

The representative harmful algal bloom (HAB, called red-tide) in the coastal waters of Korea is a dinoflagellate (Cochlodinium polykrikoides) that caused serious damages to marine ecology, fisheries, and related industry during summer season. In order to mitigate or eliminate the species before making a vast damage, early detection is most important. In general, the detection of the red-tide is counting method from filtered seawater. In spite of the advantages such as quantitative and qualitative analysis, the method is limit to the necessary time and cost. For more quickly detecting the species, new approaches are necessary. Recently hydroacoustic techniques are applied to in situ detection of aquatic organisms in seawater or freshwater environment. Based on the acoustic scattering property of the species, we are trying to develop acoustic detection system of harmful algal bloom using ultra-frequency over the 3 years. The prototype system is mainly composed of ultrasonic sensor (3.5 and 5.0 MHz), GPS, power, pulser-receiver, signal processor, network, and land-based control unit. The interactive data and control command transfer between in situ the system and land-based center was used CDMA and wire/wireless internet. For making the most of the system’s advantage, the system separately consists of two types; ship-board and mooring-type. Based on the laboratory evaluation, we tested and applied many times the system in the several conditions (with red-tide, without red-tide) of the coastal waters. Despite some modification in the near future, the system can be applied to real-time monitor or detect HAB in the coastal water and expanded to another field for detecting aquatic micro-organisms.