Design and application of ultrasonic measurement systems for Akashiwo sanguinea

Abstract

The red tide caused by Akashiwo sanguinea (A. sanguinea) has a serious negative impact on the ecological environment. Thus, it is of great importance to monitor the changes of algae cell concentration and thus forecast the red tide. This paper sets up two ulstrasonic systems based on the backscattered sound of algae cells, and uses them to measure the acoustic signals of A. sanguinea solutions of 17 different concentrations. The two systems were respectively developed on acoustic Doppler velocimenter (ADV) and single-probe development board (DB). The measured signals were analyzed to disclose the correlation between the integrated backscattered strength (IBS) and the algae cell concentration. The results show that both ADV system and DB system worked effectively when the algae cell concentration fell between 0.1×105 cells/L and 0.9×105 cells/L; The IBS continued to increase with the growth in algae cell concentration, but the growth rate was dampened when the concentration reached 2×105 cells/L, leading to fluctuations in the growing trend; the dampening is the result of the acoustic attenuation effect of the algae cells in medium-high concentration range. The test results of the ultrasonic systems agreed well with the theoretical predictions after particle size correction, indicating that attenuation compensation can enhance the system performance. The proposed systems can realize real-time monitoring of algae cell concentration, laying a solid basis for prewarning of red tide.