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Anthropogenic activities and their influences on aquatic systems is an important topic, especially considering the growing interest in using the earth's resources in a sustainable way. One of those anthropogenic activities is the introduction of renewable technologies into the aquatic environment such as instream turbines. Environmental studies around those technologies are often still ongoing due to their novelty. During the spring of 2018, juvenile individuals of two salmonid species, Atlantic salmon and brown trout were released upstream a vertical axis instream turbine in the river Dal (Dalälven) in eastern Sweden. The aim of this study was to investigate the swimming behavior of the salmonids around a small-scale prototype vertical axis instream turbine. The swimming pattern and the possible response of avoiding the vertical axis instream turbine were documented with a multi beam sonar. A control area, next to the turbine, was used as reference. No consistent results were shown for trout as they were passing the control area with a statistically high variation, and specimens were rarely observed in proximity of the turbine, neither if the turbine was operating nor at stand still. Salmon clearly avoided the operating turbine, but did not avoid the turbine when it was at stand still, and was often observed swimming straight through the turbine area. These findings indicate that operating this type of instream turbine in a river affects the swimming behavior of Atlantic salmon but is unlikely to affect its migration paths. For brown trout, the statistical results are inconclusive, although data indicate a response of avoiding the turbine. The species are in little risk to suffer physical harm as no fish entered the rotating turbine, despite very turbid water conditions.

Environmental data is crucial for planning, permitting, execution and post construction monitoring of marine renewable energy projects. In harsh conditions in which marine renewable energy is harvested, integrated monitoring platforms comprising multibeam imaging sonar systems coupled with other sensors can provide multi-dimensional data of the marine environment surrounding marine renewable energy installations. The aim of this study was to test the possibilities of observing the occurrence of fish and marine mammals using a multibeam imaging sonar system deployed at a wave power test site. The results obtained from a ten-day data set proved the platform as suitable for long time underwater monitoring and also revealed that the occurrence of fish and marine mammals was distributed across characteristic time and space domains. Large fish [>0.4 m] frequently occurred at night-time and near the benthic zone. Small fish [<0.2 m] frequently occurred during daylight and within the pelagic zone. The occurrence of seals was periodically distributed along a daily cycle, with intervals of 1 – 2 hours between maxima and minima. In conclusion, the use of multibeam imaging sonar can be a reliable technique for the qualitative and quantitative observations of fish and marine mammals in general and at marine renewable energy sites specifically, including protected and economically important species.

Past studies have revealed higher levels of biodiversity, total abundance, and size ofindividuals around offshore installations of renewable energy. This study investigated the effectsof Lysekil wave power park (area 0.5 km2) on the abundance and carapace size of decapods at theSwedish west coast. For that purpose, decapods were caught with cages during four consecutivesummers. Two types of cages were applied to catch a wide range of decapod species and sizes. Theabundance and size of decapods were not significantly different within the wave power park and upto a distance of 360 m outside of it. The catch rate, i.e., number of decapods caught in 24 h, was notsignificantly different among sampling locations but revealed inter-annual variation for both cagetypes. The results suggest a limited role of the incidental no-take zone of the small Lysekil wavepower park on the abundance and size of local decapods. However, neither were negative impacts,such as decreasing abundances or smaller carapace sizes, discovered. As an increase in the numberof marine renewable energy production sites is foreseen, a scaled-up and larger study addressingMPA networks and other environmental interactions should be considered.

Environmental impacts from wave energy generators on the local mobile mega- and macrofauna community have been investigated in the Lysekil project by Uppsala University. Offshore renewable energy installations provide hard, artificial substrates, and as such, they could act as artificial reefs. Foundations with manufactured holes served as complex habitats and foundations without served as non-complex. In this long-term study, SCUBA surveys of mobile fauna in the years 2007, 2008 and 2016-2019 were analyzed. The results show a distinct reef effect on the foundations with significant greater species richness, total number of individuals, greater values of the Shannon-Wiener biodiversity index, and greater abundance of specific reef fauna. Complex foundations accommodated a greater abundance of brown crabs than non-complex foundations, other taxa did not show differences between the two foundation types. A successional increase of species richness, numbers of individuals and Shannon-Wiener biodiversity could be revealed from the first to the second survey period. Inter-annual variation was visible throughout all taxa and years.

Techniques for marine monitoring have evolved greatly over the past decades, making the acquisition of environment data safer, reliable and more efficient. On the other hand, the exploration of marine renewable energy introduced dissimilar ways of exploring the oceans and with that arises the need for new techniques for environmental data acquisition, processing and analysis. Marine energy is mostly harvested in murky and high energetic places where conventional data acquisition techniques are impractical. Modern sonar systems, operating at high frequencies, can acquire detailed images of the underwater environment. Variables such as occurrence, size, class and behaviour of a variety of aquatic species of fish, birds, mammals, coexisting within marine energy sites can be gathered using imaging sonar systems. Although sonar images can provide high level of details, still in most of the cases they are difficult to decipher. Therefore, to facilitate the classification of targets through sonar images, this study introduces a framework of extracting visual features of marine targets that would serve as unique signatures. The acoustic measure of visibility (AVM) is here introduced as an indirect technique of identification and classification of targets by comparing the observed size with a standard value. This information can be used to instruct manual and automatic algorithms for identification and classification of underwater targets using imaging sonar systems. Using image processing algorithms embedded in Proviwer4 and FIJI software, this study found that acoustic images can be effectively used to classify cod, harbour and grey seals, and orcas through their size, shape and swimming behaviour. Data showed that cod occurred as bright, 0.9 m long, ellipsoidal targets shoaling in groups of up to 50 individuals. Harbour seals occurred as bright torpedo-like fast moving target, whereas grey seals occurred as bulky-ellipsoidal targets with serpentine movement. Orca or larger marine mammals occurred with relatively low visibility on the acoustic images compared to their body size which measured between 4 m and 7 m. This framework provide a new window of performing qualitative and quantitative observations of underwater targets, and with further improvements, this method can be useful for environmental studies within marine renewable energy farms and for other purposes.

Global electricity demand doubled between 1990 and 2016 and several countries are planning for a significant increase in offshore renewable energies along the European coast. In 2015 renewable energy accounted for more than half of the new generating capacity installed in the power sector worldwide. These activities bring up an increased interest about possible environmental impacts or additional values of the new technologies. The Wave Energy Park "Sotenäs Project" is located on the west coast of Sweden, 120 km north of Gothenburg, and was the site for environmental impact studies from wave energy generators on two sea pen species, Virgularia mirabilis (Müller, 1776) and Pennatula phosphorea (Linnaeus, 1758). Sea pens and burrowing mega fauna communities are designated threatened or declining habitats or species by the OSPAR convention. Investigations of those taxa in relation to marine renewable energies are thereby both interesting and important. A ROV aided seabed survey in the wave power park and respective control areas were primarily conducted to assess Nephrops norvegicus (Linnaeus, 1758) abundance and video footages were used to compare the abundance of the two sea pen species within the same area. Preliminary results show a significant difference between the transects and years. However, a clear increased number of individuals inside the wave power park for the two sea pen species compared to the control transects were not identified. Long-term observations and complementary studies are necessary in order to draw firm conclusions.

Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles during the installation and monitoring phase of wave energy converters. Methods and results are based on the wave energy converter system developed by Uppsala University, and our experience in offshore deployments obtained during the past eleven years. The complexity of underwater operations, carried out by either divers or remotely-operated vehicles, is emphasized. Three methods for the deployment of wave energy converters are economically and technically analyzed and compared: one using divers alone, a fully-automated approach using remotely-operated vehicles, and an intermediate approach, involving both divers and underwater vehicles. The monitoring of wave energy converters by robots is also studied, both in terms of costs and technical challenges. The results show that choosing an autonomous deployment method is more advantageous than a diver-assisted method in terms of operational time, but that numerous factors prevent the wide application of robotized operations. Technical solutions are presented to enable the use of remotely-operated vehicles instead of divers in ocean renewable technology operations. Economically, it is more efficient to use divers than autonomous vehicles for the deployment of six or fewer wave energy converters. From seven devices, remotely-operated vehicles become advantageous.

Wave energy research is primarily focused on the technical developments of energy conversion but the parallel evaluation of environmental effects related to wave energy is also essential and reflects sustainable development of renewable energy. At the west coast of Sweden, 120 km north of Gothenburg, the Wave Energy Park “Sotenäs Project” is located. This area has been the location of environmental impact studies from wave energy generators on the macro crustacean species Nephrops norvegicus (Linnaeus, 1758), the Norway lobster. The Norway lobster is an ecologically as well as economically important species in Sweden and across Europe. The aim of this preliminary study was to detect possible positive or negative effects on numbers of individuals by the presence of the wave energy generators and the created “no take” zone. For that purpose, ROV aided seabed recordings of the characteristic Norway lobster burrow entrances were conducted inside the Wave Energy Park and respective control areas in 2016 and 2017. Preliminary results do not show a clear distinct result between the different transects and years. Long-term observations and complementary studies are necessary to draw conclusions and outweigh extreme and rare events of annual one-time samplings.