Coordinateurs du projet
Context
The EchoSonde project, winner of the 2016 WEAMEC Research call for projects, and its follow-up, the EchoSondeBis project, winner of the 2020 WEAMEC Research call for projects, focus on studying the impacts of MRE.
The Pays de la Loire region will be home to two offshore wind farms. The impacts of MRE on organisms living in the water column are largely unknown at present. However, these organisms play an important role in producing photosynthesis and transferring most of the energy that feeds other compartments of marine ecosystems.
The EchoSonde project has made progress in overcoming the instrumental barrier linked to the detection and identification of organisms present in the water column in eutrophic, turbid coastal environments, and the barrier linked to data analysis enabling the statistical identification of species present and the description of their spatio-temporal dynamics. However, excessive logistical constraints prevented the sustainable deployment of a land-based EchoSonde connected in real time during the first phase. The EchoSondeBis project therefore aims to deploy a simplified, autonomous integrated acoustic observatory in order to alleviate technological constraints.
Scientific breakthroughs and innovation
Echosonde Observatory on MRE Impact Assessment:
- Development of EchoSonde: integrated acoustic observatory of the water column comprising an innovative broadband sounder that improves the identification of acoustic targets compared to conventional narrowband sounders.
- Continuous acquisition of data on the pelagic ecosystem with real-time sampling control
- Development of methods for real-time processing of large data flows from the EchoSonde
Expected technical and economic impact
- Methods for integrated acoustic monitoring of the impacts of marine renewable energy (MRE) on the pelagic ecosystem
- Unique data on the coastal pelagic ecosystem prior to the construction of the Saint-Nazaire offshore wind farm.
Demonstrator
The EchoSonde & EchoSondeBis projects aim to develop a prototype integrated acoustic observatory for the water column to assess the impact of MRE on the coastal pelagic ecosystem. The demonstrator was deployed at Centrale Nantes’ SEM-REV offshore test site.
Results
The echo sounder used in the Ec(h)oSonde project enables millimeter-sized mesozooplankton organisms to be detected and characterized using broadband acoustics up to 30 m from the observatory.
Dense scattering layers (SSLs) composed of zooplankton, small fish, and jellyfish were observed in the spring. The SSLs were much less dense in the fall.
Millimeter- to centimeter-sized jellyfish were the dominant organisms around the SEM-REV site in the spring.
Extensive layers of dead planktonic organisms were observed in the spring of 2018, following a very high production of microalgae.
Millimeter-sized crustaceans dominated the pelagic zooplankton community in the fall.
The EchoSondeBis autonomous broadband echo sounder acquired data every hour at the SEM-REV site from June to November 2021. These new acoustic data enabled detailed observation for the first time in France of ecological processes at fine temporal scales not resolved by sea campaigns: migration of fish to the surface at night and effects of tidal currents and internal waves on pelagic organisms. Significant monthly variations in the abundance and density of schools of small pelagic fish and micronecton organisms (fish larvae, jellyfish, etc.) were also observed for the first time thanks to data from EchoSondeBis.
An original method for analyzing broadband acoustic data was developed as part of the project. It was presented at the annual meeting of the ICES Working Group on Fisheries Acoustics, Science and Technology on April 20, 2021.
Perspectives
Capitalize on the experience gained during the project to develop a more generic, comprehensive, and robust EchoSonde 2.0, which could be deployed at all marine renewable energy production sites to assess their impact on pelagic ecosystems.
