There are ambitious plans in Europe and elsewhere for marine renewable energy developments (MREDs), such as wind, wave, and tidal-power devices. The construction and operation of MREDs will lead to, among other things, the emission of electromagnetic fields (EMF), underwater sound and vibrations into the marine environment. Understanding of EMF emissions from MREDs is limited and studies on potential impacts – for example on migratory fish – are in its infancy.
Underwater sound impacts from MREDs have become a particularly important environmental issue. This is because water is an excellent medium for sound transmission. As a consequence, many forms of marine life use sound as their primary mode of communication, to locate a mate, search for prey, avoid predators and hazards, and for short- and long-range navigation.
Activities generating underwater sound can affect these vital life functions and, since sound can be far ranging, the spatial scale of impacts can be quite large as well. Research has shown that some species such as the harbor porpoise are sensitive to disturbance due to wind-farm construction sound. It is also possible that construction sound could lead to temporary or even permanent hearing loss in marine mammals and fish, depending on the overall sound energy (the ‘acoustic dose’) that is received over time.
Yet, there are many open questions with regard to impacts of MRED related sound and vibration on marine life. These information gaps pose challenges to the implementation of MREDs, one such as the determination of monitoring requirements and risk assessment for prioritised receptor animals. Scope In a project for the European Union Commission, Directorate-General for Research and Innovation, we undertook a study of the environmental impacts of noise, vibrations and electromagnetic emissions from MREDs (Marine Renewable Energy, Vibration, Electromagnetic fields and Noise – MaRVEN).
The aims of MaRVEN were to critically review the available scientific evidence and significance of those impacts and then make recommendations on solutions to mitigate or cancel any identified negative impacts. The investigation comprised several tasks including:
• Provision of an historical review of the publications related to environmental impacts of marine renewable energy developments
• An in-depth analysis of studies on the environmental impacts of noise and vibrations during installation and operation of marine renewable energy devices
• An in-depth analysis of studies on the environmental impacts of electromagnetic emissions during the operation of marine renewable energy devices
• An in-depth analysis of the current norms and standards related to noise, vibrations and EMF for marine renewable energy systems
• Performance of relevant on-site measurements and field experiments to validate and build on the results obtained in above studies
Results Historical review of environmental impacts of MRED The database for the literature on impacts of marine renewables energy devices (MREDs) on marine life comprises more than 1,200 sources. The database has a search engine with initial searches based on broad topics and available author names. We also present a historical review of publications related to the environmental effects of MREDs. Here, the full ranges of impacts are considered.
The review provides a summary of all possible impact pathways and biological receptors and analyses effects together with the prioritisation of the various environmental effects of marine renewable energy devices due to their effects at a population or ecosystem level. In-depth analysis of studies on effects of noise and vibration The main conclusions were that elements of the exposure assessment (i.e. the description of the sources of sound for MREDs and the calculation of the sound exposure) have made major progress since the time of previous benchmark reviews (i.e. Thomsen et al. 2006).
In general, it is clear that sound produced during construction of MREDs has the greatest potential for conflict with marine life while operational sound has been much less of a concern. With regard to the dose-response assessment, knowledge has been gained on the behavioural response mainly due to construction of MREDs in a few species (i.e. harbour porpoises, harbour seals, and some fish (cod, sole, and mackerel) either in the field or in laboratory.
Yet, results on effects on other species and taxa are very sparse or non-existent. Finally, much progress has been made with regard to risk mitigation especially for impact pile driving. A paper on vibration including the definition of the term ‘vibration’ against the use of ‘sound’ and ‘particle motion’ was commissioned outside the MaRVEN team to the Institute for Sound and Vibration, University of Southampton.
Here, a working definition was adopted with ‘sound’ as a vibration existing in a fluid, and ‘vibration’ the energy propagating through wave motion in a solid. This distinction is important for impact assessments as marine life in the water column will mainly experience ‘sound’ (measured as pressure and particle motion), whereas life forms on the ground (for example flatfish) will likely experience both, and those organisms living in the sediment will receive vibrations.
Yet, the exact amount of vibration on the seafloor, resulting from construction and operation, is not known and it is transferred in to the water column as sound. It is currently not clear if vibrations will lead to any measurable or significant impacts on bottom living marine life.
The complete study is here: file:///I:/01%20For%20posting/Nosie%20study%20MaVEN%208ENN_002.pdf
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