Report of the Round Table Session
Thomsen, F.1*, Lepper, P.2*, Bald, J.3, Blondel, P.4, Grellier, K.5, Norro, A.6, Tougaard, J.7, and Wilson, B.8
1 DHI, Denmark
2 Loughborough University, UK
3 AZTI, Spain
4 University of Bath, UK
5 Natural Power Consultants, UK
6 RBINS, Belgium
7 Aarhus University, Denmark
8 SAMS, University of the Highlands and Islands, Scotland
This report can be referenced as:
Thomsen, F., Lepper, P., Bald, J., Blondel, P., Grellier, K., Norro, A., Tougaard, J., and Wilson, B. (2015). Report of the Renewable Energy Session, oceanoise2017, Vilanova i la Geltrú, Barcelona, Spain, 10-15 May. (Editors Michel André & Peter Sigray).Retrieved from http:// oceanoise2017.com
The discussion was divided into a first section, where the audience addressed specific questions to the presenters and a second part, where the questions distributed by the chairs beforehand were discussed.
One topic covered in the first part was the distribution of sound sources in the water column (i.e. in different water depths and horizontal distribution). Another issue discussed was fouling impacts, which is moving up the agenda now that more devices are available and accruing appreciable submerged times. It is likely that fouling could affect acoustic signatures of moving wave / tidal-stream energy converters. One participant mentioned the need for sound data from moored ships (as used for maintenance and also during installation/recovery). The discussion also covered the biological implications of ‘low-level noise’ (i.e. behavioural impacts). Synergistic / cumulative effects from a variety of devices were discussed as well. In this context, it was mentioned that operational wind turbine platforms may in some cases act as fish aggregation devices and that fish in the vicinity of these turbines could be affected by changes in the local soundscape due to operational sound. In this context, there was a mention of the UK-based FLOWBEC project (FLOW and Benthic ECology 4D). This project aimed to improve the understanding of how the physical behaviour of the water such as currents, waves and turbulence at tide and wave energy sites influences the behaviour of marine wildlife, and how tide and wave energy devices might alter the behaviour of such wildlife. On a more general note, it was argued that there is a push-pull situation with regards to the implementation of marine renewables and the protection of marine life. In general, there seems to be a lack of understanding of the changes in soundscapes due to the implementation of marine renewable energy devices.
In the second part of the discussion, the speakers and audience considered some high-priority issues. Mentioned were:
- Impacts of pile driving on commercially important and / or protected fish species such as herring. It was mentioned here that, although the topic is important, it will be challenging to study as the reactions of schooling or spawning fish could be rather subtle and therefore difficult to measure despite their subsequent importance.
- Impacts of MREDs on invertebrates. Studies in the Baltic have shown no differences between the species composition on foundations in an offshore wind farm compared to a nearby stony reef. However it has to be considered that the life cycle of many marine invertebrates is short, so that impacts during construction would go undetected. More measurements, in more varied locations, are therefore necessary.
- Attraction of fish to underwater structures (i.e. offshore turbine foundations) and trade-offs between costs (i.e. noise exposure) and benefits (i.e. availability of food and protection against predators and fishing).This trade off could lead fish to receive excessive and chronic noise exposure.
- Cumulative impacts from several devices (vibration / noise) or cables (additional EMF impacts). How individual animals respond to multiple devices compared to single devices is not yet clear and impinges on issues such as collision risk modelling and behaviour within or around arrays of different shapes and designs.
- Ecosystem changes for example changes in wave regime and knock-on effects on turbidity in combination with noise. Multi-physical and biological disciplines approaches to assessment of impacts becoming a higher priority.
- How might/does the behaviour of an animal vary within an array of operational devices (wind, wave, tide) compared to near a single device?
- Do we know enough about sources of sounds to prioritise research / regulation for marine renewables?
- What marine life is most critically affected?
- What are the biggest knowledge gaps with regards to dose-response studies?
- How are cumulative impacts being best assessed?
- How does sound rate against other impacts?
- What are the key issues with regards to marine renewables and noise?
- What issues can be closed as, from a risk assessment perspective, they are not critical?