UACE2025: Dynamics of the echo-reflecting layers in a deep lake: implementation of Acoustic Doppler Current Profiler (ADCP) for ecosystem analysis

• Session:
  Acoustic Monitoring of Marine Ecosystem
• Paper:
  Dynamics of the echo-reflecting layers in a deep lake: implementation of Acoustic Doppler Current Profiler (ADCP) for ecosystem analysis
• Author(s):
  Ernst Uzhanskii, Boris Katsnelson, Ilia Ostrovsky
• Abstract:
  Aquatic systems are inhabit by various echo-reflective objects (fish, plankton, suspended particles, etc.), which dynamics and interactions is still poorly understood because of huge spatiotemporal heterogeneity, which cannot be properly addressed by using traditional limnological methods. The main aim of this study is to investigate spatiotemporal dynamics of main echo reflecting objects in a deep large lake in response to external forcing (wind, solar radiation, stratification). The study was conducted on Lake Kinneret (Israel) during January-February 2017, when the lake supposed to be completely mixed. High-resolution data on volume backscattering strength and water currents were measured with two stationary deployed Teledyne Sentinel ADCPs — V20 (1000kHz) and V50 (500kHz) deployed at Station_H (10 m) and Station_F (19 m), respectively. We also used the meteorological data (wind speed, solar radiation, air temperature) and thermistor chain data installed at Station_F (courtesy of A. Rimmer and Y. Lechinsky). We showed that:\n• The appearance of thin high-intensive echo-reflective layer near the water surface was associated with strong wind (above 10 m s-1). This layer was filled with gas bubbles produced by breaking of surface waves. \n• An upper- and mid-water echo-reflecting layer displayed distinct near-diurnal variability during period of development of gas-containing cyanobacteria. It is suggested that the changes in thickness and intensity of this layer was associated with vertical migration of the cyanobacterium in response to development/vanishing of thermal stratification responding to the variable energy balance between the wind input and heat flux. \n• A strong backscatter layer near the bottom was the most distinct at shallower station. It was likely caused by resuspension of particles or lateral particle transfer from the littoral zone or watershed area.\nThis work demonstrate that remote acoustical methods can be a robust tool for long-term study of spatial variability and temporal dynamics of biological and non-biological echo-reflecting objects in nature.\n
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Contact details

• Contact person:
  Mr Ernst Uzhanskii
• e-mail:
  
• Affiliation:
  Leon H. Charney School of Marine Sciences, University of Haifa, Israel
• Country:
  Israel