Approaches to assessing the impact of marine renewable energy converters (MRECs) on coastal marine environments

Australia currently produces more than 18,600 petajoules of energy annually. Only 2% of this energy is produced via renewable means of energy production with the remaining 98% produced by non-renewable means such as fossil fuels and natural gas. With the 2020 October budget announcement by the Australian Government that the Australian Renewable Energy Agency (ARENA) will continue to be funded for a further 10 years, there is financial incentive and capacity to continue the development of marine renewable energy technologies in Australian coastal waters. The ecological impacts of these technologies, however, are not well understood. Marine Renewable Energy Converters (MRECs) are typically situated in volatile, dynamic environments which creates challenges for conducting robust ecological research to determine impact. Furthermore, these ecosystems usually contain many species with conservation and/or commercial value. Given studies into the impact of MRECs are very limited, developing a more robust framework to determine impact is timely. This research investigated the potential impacts of the introduction of MRECs on coastal marine ecosystems. Specifically, it assessed the current state of MREC technologies, the sources of impact of MRECs and the component within a marine ecosystem susceptible to those impacts and undertook robust quantitative and qualitative studies for assessing these impacts. There are four fundamental types of MRECs – wave, tide, current and ocean thermal. With over 350 MREC designs and developers worldwide, many of these designs have reached the environmental approval stage in their respective regions with little identification of the environmental impacts of these devices. Chapter 2 highlighted that the main sources of impact were those that occur during installation and assembly of the MREC, caused by the presence of the MREC structure itself, and the resultant artificial light and noise associated with the functioning of MRECs. Marine mammals, seabirds and migratory shorebirds, fishes, large invertebrates such as crustaceans and benthic communities are all likely to be impacted by these sources. Impacts recorded can be both positive, for example providing haul-out sites for pinnipeds and negative, for example through the potential for seabirds to collide with turbines. In Chapter 3 I identify and describe a rigorous identification framework for assessing the impacts of an MREC on components of a coastal system. The framework involves the use of both quantitative and qualitative research designs. Two examples of these research designs provided are a modified Before-After-Control-Impact (BACI) design for quantitative analysis of ecosystem response and Loop Analysis, a technique of qualitative modelling of socio-economic and functional group response to a perturbation in a model system. In Chapter 4 I used a modified BACI design and characterised fish and crustacean assemblages at control sites and the proposed site of a wave-energy converter (i.e., impact site) utilising baited underwater video. Sampling was undertaken twice before the installation and revealed the impact site had a higher relative abundance of species but there was no statistical difference in number of individuals, number of species and species diversity among the control/impact sites. Unfortunately, due to a shipping accident the MREC was not installed at the site and no ‘after’ sampling was possible. Nonetheless, the sampling before installation highlighted the natural ecological variation likely at many sites of proposed MRECs and the importance of a rigorous approach to determining impact. In Chapter 5 I used qualitative modelling (Loop Analysis) to make predictions of the impact of the introduction of an MREC into the Western Bass Strait Shelf Transition, southern Australia, a region of high potential for marine renewable energy production but also a region with a large commercial fishery and high marine conservation value. Models included socio-economic and biological components and focussed on the effects of an MREC on five components of the model ecosystem: macroalgae, carnivorous and herbivorous fish species, large commercially harvested crustaceans, migratory shorebirds and seabirds. Both positive and negative effects of the MREC on the different components of the ecosystem were revealed by the models. However, the models showed that impact will be dependent on that component first impacted and an overall model of the whole system indicated that while the majority of components have the potential to be positively impacted, there is a high level of uncertainty in the level of confidence in this result. This research provides a framework for assessing the impact of MRECs on coastal marine environments. An increasing number of MRECs are being developed, with the potential for broad impacts on marine ecosystems. The research required to fully understand these impacts will take significant time and resources and is likely to vary depending on the ecosystem itself, the type of MREC being installed and the regulatory requirements of the country