Marine Renewable Energy Technology and Environmental Interactions

It is now widely recognized that there is a need for long-term secure and suitable sustainable forms of energy. Renewable energy from the marine environment, in particular renewable energy from tidal currents, wave and wind, can help achieve a sustainable energy future. Our understanding of environmental impacts and suitable mitigation methods associated with extracting renewable energy from the marine environment is improving all the time and it is essential that we distinguish between natural and anthropocentric drivers and impacts.

Increasing interest is apparent in marine energy resources, particularly tidal and wave. Some TeraWatts of energy propagate from the world’s oceans to its marginal seas in the form of surface waves (≈ 2 TW) and tides (≅ 2.6 TW) where that energy is naturally dissipated. The seas and coastlines around the UK and its neighbours are notable for dissipating a significant fraction of the global energy of waves (≈ 50 MW km⁻¹ on the Atlantic coast) and especially tides (> 250 GW north of Brittany). Displacing a significant fraction of the natural dissipation by energy capture is a tempting and reasonable proposition, but it does raise technical and environmental issues. Sustainable exploitation of the energy needs to consider diverse effects on the environment, waves and tides having a role in maintaining the shelf sea, coastal, estuarine and shoreline environment through associated advection, stirring and other processes. Tides are particularly significant in controlling the stratification of shelf seas and their flow characteristics. Surface waves are more important in determining conditions nearshore and in the intertidal zone. Also, the exploitation of wave and tidal resources is only practical economically and technologically at a limited number of energetic and accessible sites, and societal and ecological considerations inevitably narrow the choice.

As part of the UK government’s objective to deliver an increasing proportion of electricity from renewable sources, West Mainland, Orkney, is at the forefront of the development of wave-energy extraction devices. Exposure to wave energy plays a dominant role in shaping the Orkney landscape and determining the ecological community, but little is known of the consequences of commercial scale removal of energy from the environment. An extensive long-term monitoring programme to assess the impacts of altering wave-energy exposure on these rocky shores alongside responses to other systemic forcing agents such as climate change is continuing. Within the programme are photographic surveys, including quadrat and fixed viewpoint techniques, littoral studies of sentinel species, and the development of cost-effective wave-energy quantifying devices. Software has been developed to analyse images efficiently, to produce quantitative data on species and biotope coverage. Additionally, extensive surveys along the shoreline provide detailed image records, including areas without prior scientific description, and have helped identify locations of environmental sensitivity. Collectively, the data provide a comprehensive pre-development baseline along this important coast.

Marine renewable energy conversion typically takes place at locations characterized by harsh physical parameters that challenge monitoring of the marine environment. These challenges are caused both by the lack of experience on what to expect in terms of impact, but also by a general lack of methods proven suitable for the monitoring of high-energy subtidal marine habitats. Here, the first offshore windfarm to be built in Norwegian waters, a project called Havsul I, is used as a model to provide (i) an overview contrasting the known effects and monitoring methods used at more sheltered offshore windfarms with those expected at a rocky, high energy site; (ii) a description and short assessment of the physical environment (bathymetry, current, wave and wind data) and marine assemblages at the site, (iii) an assessment of five methods used during the baseline study at Havsul I, including sediment grabs, sampling of assemblages from kelp stipes, video mosaics for rocky bottom benthic assemblages, traditional fishing gear for fish community evaluation, and C-PODs for harbour porpoise presence.

Offshore renewable energy development (ORED) could induce local ecological changes and put species assemblages of conservation interest at risk. If well planned and coordinated, however, ORED could be beneficial to the local subsurface marine environment in several aspects. Acknowledging the scale of ORED, there is increasing interest in the opportunities offered by the resulting changes in fishing patterns, such as exclusion or limitation of bottom trawling, in wind and wave farms. Areas encompassing several square kilometres may in some important aspects resemble Marine Protected Areas, and wind and wave-energy foundations and other associated structures can function as artificial reef modules and enhance the local abundance of marine organisms, including commercially important fish and crustaceans. It is also possible that floating offshore energy devices can function as fish aggregation devices for pelagic fish. Here, the potential influence of offshore wind and wave farms on fish and commercially important crustaceans is described, mentioning the uncertainties with regard to positive and negative effects on benthic and pelagic assemblages and specific species.

In the marine environment there are natural magnetic and electric fields associated with both physical and biological sources, and there are anthropogenic electromagnetic fields (EMFs) that permeate it. Many marine animals can detect electric and magnetic fields and utilize them in such important life processes as movement, orientation and foraging. Here, these EMFs are explored and discussed in terms of how they arise, their properties (particularly those that are measurable) and the animals that have the ability to detect them. Then the evidence base for whether anthropogenic EMFs can affect sensitive receptor animals is explored. As marine renewable energy developments (MREDs) expand rapidly worldwide, with multiple devices and networks of subsea cables that emit EMFs into the marine environment, it is necessary to focus on their interaction with marine animals. The MRED industry has to take EMFs into account, so the industry perspective is also covered. Finally, suggestions are made on how research on EMFs associated with MREDs (and other sources) and its interaction with marine animals should advance in future.

The rapid increase in marine renewable energy installations (MREIs) will result in the placing of many novel man-made structures within seabird foraging habitats, and such structures could potentially impact seabird populations directly and indirectly, positively and negatively. However, whether these potential impacts represent real ones, such that they cause detectable trends in population levels, remains unknown. Changes in population dynamics of seabirds are driven primarily by rates of reproduction and adult and juvenile survival, all three of which are impacted by foraging success. Therefore, revealing precisely how MREIs can affect seabird foraging success through changes in foraging behaviour is key to understanding whether large-scale installations could have impacts at a population level. Discussion focuses on how to define foraging habitat and how MREIs might impact those habitats and foraging behaviour indirectly by changes in oceanographic processes and prey characteristics. Foraging behaviours are also likely to be more directly impacted by MREIs, so focus here is also on how changes in foraging behaviour during the more constrained breeding season can influence reproductive output by altering individual energy budgets. A third and more-direct potential impact of MREIs on foraging behaviour is changes in diving behaviour. Throughout, relevant gaps in current knowledge that need to be addressed in order to make robust predictions as to how MREIs might impact seabird populations are highlighted.

The wave climate along the west coast of North America presents great opportunities for the development of offshore renewable energy, yet initial assessments of the potential ecological effects of wave energy development have only just started. An enhanced regional understanding of the biological resources in the area is needed, and a key information gap is the distribution of both physical substrata and important biological communities. An initial renewable energy project targeted for Oregon is a mobile Ocean Test Facility developed by the Northwest National Marine Renewable Energy Center (NNMREC), led by Oregon State University (OSU), for testing wave energy converters. In addition, a number of wave and wind energy projects have been proposed for the Pacific Northwest of the US. In this chapter, an overview of the oceanographic characteristics of the region is presented, summarizing some of the interactions of concern, and highlighting baseline research projects focused on seabirds, marine mammals and benthic ecology in preparation for siting and deploying the NNMREC Ocean Test Facility and offshore renewable structures generally in the region.

Commercial-scale devices to extract energy from tidal streams and waves may be new, but an associated industry is developing fast. In most countries, device introduction will require investigation and some level of proof that they do not unduly harm local wildlife. Of the impacts that they might have, the emission of acoustic energy (noise) into the marine environment is important. In operation, it is possible, though unlikely, that they will emit sufficient noise to cause auditory damage to sensitive species, but some level of area avoidance/attraction and masking is likely. Nevertheless, all such devices will require perceivable acoustic signatures for animals to detect and avoid colliding with them. To understand these issues, information on operational device acoustic characteristics is required along with information on existing background noise levels at sites suitable for extraction of marine energy. However, the energetic features of these locations with intense lateral, vertical or oscillatory motion mean that conventional methods of underwater sound recording are unsuitable. Here new methods for sound measurement specifically tailored to tidal-stream and wave-energy sites are introduced. The methods are illustrated following performance tests and real measurements at the European Marine Energy Centre tidal test site in Orkney, UK.

Currently, there is great uncertainty surrounding the environmental impacts of tidal turbines on marine mammals; one major concern derives from the potential for physical injury through direct contact with the moving structures of turbines. Collecting data to quantify these risks is challenging and methods for measuring movements underwater and interactions with turbines are limited. However, potential tools include a small number of cutting-edge technologies that are being used increasingly for research and monitoring; these include animal-borne telemetry, and active and passive acoustic tracking. Recent developments in these technologies are described along with their means of application in measuring fine-scale movements and avoidance or evasion responses by marine mammals around turbines. From a risk-characterization perspective, each technique can provide information to inform risk assessments or help parametrize collision risk models; however, each has its associated benefits and drawbacks and it is clear that, in isolation, none of them can provide all the data needed to address the problem. The three approaches appear highly complementary, with the strengths of one complementing the weaknesses in others; the solution to characterizing the risks posed by tidal turbines is likely to be a combination of such techniques.

The development-plan-based approach being taken to the establishment of the offshore wind, wave and tidal sectors in Scotland is outlined. The strategic planning framework and processes leading to the development of Draft Plans are explained, along with the relationships between these and the sustainability appraisal process. Detail is also given of the spatial planning methods used to identify development opportunities for one sector in Scottish waters.

The background to and outcomes of the Environmental Monitoring Programme (EMP) required by statutory regulators for the deployment of the SeaGen tidal turbine in Strangford Lough, Northern Ireland, an area with many conservation designations, are described. The EMP, which was set within the context of an adaptive management approach, considered possible effects of the device on local populations of seals and harbour porpoises, representative seabirds and benthic communities. The studies on seals were carried out on both local and regional scales. The ecological studies were complemented by detailed field and hydrodynamic modelling investigations together with a programme of mitigation measures designed to reduce collisions between seals and turbine rotors. In general only minor statistically significant changes in abundance, distribution and animal behaviour patterns were recorded, principally associated with small distributional shifts close to the turbine structure and with the likelihood that these changes were ecologically of little significance. The seal–rotor collision mitigation studies provided a base for the establishment of acceptable collision risk strategies. The EMP highlighted observational, methodological and statistical challenges in assessing the environmental consequences of marine energy devices. A brief review of related studies in Strangford Lough is included.