Offshore windmill farms: threats to or possibilities for the marine environment

Exploring the impact of magnetic fields related to submarine power cables on the American mud crab Rhithropanopeus harrisii: A behavioural and physiological perspective

The number of submarine cables in marine environment is increasing. Thus, marine organisms, especially benthic invertebrates are exposed to magnetic fields generated by those cables. The aim of the study was to determine the effect of static magnetic field (SMF) and electromagnetic field (EMF) on the behaviour and physiology of Rhithropanopeus harrisii during a series of laboratory experiments. Neither SMF nor EMF significantly affected oxygen consumption rate, ammonia excretion rate and haemolymph osmotic concentration after 8-day exposure. In experiment related to spatial preferences crabs showed a clear attraction to EMF and were more active in EMF than in the geomagnetic field. In small areas without additional cues (locomotor activity experiment) EMF did not elicit changes in activity, whereas in experiment on conspecific behaviour crabs were more active and socially interactive. In SMF neither attraction nor avoidance behaviour was observed but decrease in activity and less interaction between individuals was noted.

Environmental implications of future offshore renewable energy development in Aotearoa New Zealand

Global climate mitigation efforts seeking to reduce greenhouse gas emissions require more renewable energy generation and utilisation. In Aotearoa New Zealand there are initiatives underway to develop offshore wind, or in the future, arrays of tidal turbines or wave energy converters, as a new energy resource. Here we synthesise available knowledge from international developments in offshore windfarm installations and discuss in a local Aotearoa New Zealand context. Aspects described include habitat modification, consequences of physical water column changes, and effects on benthic organisms, fish and fisheries, seabirds and marine mammals. Importantly, there is a need to adhere to Te Tiriti o Waitangi which defines Māori sovereign rights and expectations in terms of guardianship of resources (kaitiakitanga). Based on recent regulatory applications in marine spatial planning, where developments have been subject to the precautionary principle for environmental impacts, comprehensive environmental information will be critical for obtaining approval to proceed. The present synthesis identifies environmental pressure-points, footprints, and knowledge gaps, such as New Zealand-specific seabird and marine mammal behaviour and discusses potential opportunities to leverage the positive impacts of marine renewable energy developments.

Offshore wind farm operation contributed to a slight improvement in seawater quality along the Jiangsu Coast, China

The rapid growth of offshore wind farms (OWFs) is driven by concerns for energy security and climate change mitigation. However, their impact on marine environments remains poorly understood due to limited research. This study analyzes the effects of an OWF along China's Jiangsu Coast on seawater quality using data from different development phases. Results show the major pollutants were different across phases. Heavy metal pollution reached alert levels during construction compared to the safe levels observed in the pre-construction and operational phases, mainly due to increases in Pb, Cd, and Hg concentrations. Eutrophication was mild throughout all periods but exhibited a continuous decrease, primarily attributed to reductions in PH and COD concentrations. As a result, the comprehensive pollution level during construction was increased, but it was improved to a clean level during the operational phase. Besides, significant variations were observed in the spatial distribution patterns of major pollutant indices across different scenarios. These changes may stem from a combination effect of land-based pollution, aquaculture, OWF-induced disturbances to atmosphere and hydrodynamics, OWF-related drain and leakage contamination, and marine management policies. Understanding these effects informs OWF optimization, rational wind resource utilization, and marine ecology protection.

Beneath the blades: Marine wind farms support parts of local biodiversity - a systematic review

Offshore wind energy developments in European waters are rapidly expanding to meet the increasing global demand for renewable energy. These developments provide new substrates for species colonisation, but also introduce changes in electromagnetic fields, noise levels, and hydrological conditions. Understanding how these man-made structures affect marine biodiversity across various species groups is crucial, yet our knowledge in this field remains incomplete. In this synthesis paper, based on 14 case studies conducted in northeastern Atlantic (North, Irish and Baltic seas), we aggregated species-level data on abundance, biomass, and other quantity proxies spanning the entire food chain from invertebrates to mammals, and compared these variables between wind farms and nearby control sites. Overall, our analysis revealed that in wind farm areas, species tend to occur at higher quantities than in control areas. Additionally, we noticed a slight trend where the positive effect of wind farms was more pronounced in newly established ones, gradually diminishing as wind farms aged. None of the tested covariates (depth, distance from coastline, years in commission) nor species' characteristics (habitat and spawning types, trophic level) showed statistical significance. When examining species groups individually, there was a tendency for wind farm areas to harbour higher quantities of polychaetes, echinoderms and demersal fishes. These findings suggest that wind farms contribute to the so-called reef-effect, providing shelter and food supplies to their inhabitants and acting as no-take-zones. Our results support the idea that wind farms could serve as zones of increased local biodiversity, potentially facilitating spillover effects to nearby areas for certain species groups. Further studies are necessary to gain a more comprehensive understanding of the adverse effects of wind farms on associated biodiversity, while also exploring avenues to amplify their positive impacts.

Potential marine benthic colonisers of offshore wind farms in the English channel: A functional trait-based approach

Offshore wind farms (OWFs) have gained attention as a promising alternative to conventional energy sources. However, their installation and operation may have multiple ecological impacts on the marine environment, including the "reef effect". The reef effect is the colonisation of wind turbines and other artificial substrates by benthic organisms, which has a major impact on marine biodiversity as it changes community assemblages and ecosystem functioning. We conducted a two-step study to predict the reef effect of a future OWF (Dunkirk, northern France). First, we explored similarities between colonisers of existing OWFs and those of other hard substrates (oil and gas platforms (O&GP) and hard substrates in the English Channel (HSEC)). We then analysed functional traits to determine a trait profile of potential colonisers of Dunkirk's OWF. Statistical analyses revealed that OWF and O&GP communities were more similar to each other than to that of HSEC. Comparing the three communities revealed that they shared 157 taxa, which could be potential colonisers of Dunkirk's future OWF. The functional profile revealed that OWF colonisers were species ranging from 10 to 100 mm in size, with gonochoric reproduction, pelagic and planktotrophic larvae, a life span of less than 2 years or 5-20 years, were sessile, and were carnivores or suspension feeders. Functional trait analysis revealed that during their intermediate stage of development, OWF benthic communities have a functional richness and diversity (0.68 and 0.53, respectively) similar to those of HSEC communities (0.54 and 0.50, respectively). However, based on using O&GP as a long-term view of the colonisation of OWFs, functional richness and diversity could decrease during the climax stage (0.07 and 0.42, respectively).

Introducing energy into marine environments: A lab-scale static magnetic field submarine cable simulation and its effects on sperm and larval development on a reef forming serpulid

Non-chemical sources of anthropogenic environmental stress, such as artificial lights, noise and magnetic fields, are still an underestimate factor that may affect the wildlife. Marine environments are constantly subjected to these kinds of stress, especially nearby to urbanized coastal areas. In the present work, the effect of static magnetic fields, associated with submerged electric cables, was evaluated in gametes and early life stages of a serpulid polychaete, namely Ficopomatus enigmaticus. Specifically, biochemical/physiological impairments of sperm, fertilization rate inhibition and incorrect larval development were assessed. We evaluated differences between two selected magnetic field induction values (0.5 and 1 mT) along a range of exposure times (30 min-48 h), for a sound evaluation on this species. We found that a magnetic induction of 1 mT, a typical value that can be found at distance of tens of cm from a submerged cable, may be considered a biologically and ecologically relevant for sessile organisms and for coastal environments more generally. This value exerted statistically significant effects on membranes, DNA integrity, kinetic parameters and mitochondrial activity of sperm cells. Moreover, a significant reduction in fertilization rate was observed in sperm exposed to the same magnetic induction level (1 mT) for 3 h, compared to controls. Regarding early larval stages, 48-h exposure did not affect the correct development. Our results represent a starting point for a future focus of research on magnetic field effects on early life stages of aquatic invertebrates, using model species as representative for reef-forming/encrusting organisms and ecological indicators of soft sediment quality.

Large-scale effects of offshore wind farms on seabirds of high conservation concern

The North Sea is a key area worldwide for the installation of offshore wind farms (OWFs). We analysed data from multiple sources to quantify the effects of OWFs on seabirds from the family Gaviidae (loons) in the German North Sea. The distribution and abundance of loons changed substantially from the period before to the period after OWF construction. Densities of loons were significantly reduced at distances of up to 9-12 km from the OWF footprints. Abundance declined by 94% within the OWF + 1 km zone and by 52% within the OWF + 10 km zone. The observed redistribution was a large-scale effect, with birds aggregating within the study area at large distances from the OWFs. Although renewable energies will be needed to provide a large share of our energy demands in the future, it is necessary to minimize the costs in terms of less-adaptable species, to avoid amplifying the biodiversity crisis.

Do magnetic fields related to submarine power cables affect the functioning of a common bivalve?

The aim of the study was to determine the effect of static magnetic field (SMF) and electromagnetic field (EMF), of values usually recorded near submarine cables, on the bioenergetics, oxidative stress, and neurotoxicity in the cockle Cerastoderma glaucum. Bivalves maintained a positive energy balance, but the filtration rate and energy available for individual production were significantly lower in SMF-exposed animals compared to the control treatment. No changes in the respiration were noted but ammonia excretion rate was significantly lower after exposure to EMF. Changes in the activities of antioxidant enzymes and the lipid peroxidation were not observed however, exposure to both fields resulted in increased protein carbonylation. After exposure to EMF a significant inhibition of acetylcholinesterase activity was observed. As the present study for the first time revealed the oxidative damage and neurotoxicity in marine invertebrate after exposure to artificial magnetic fields, the need for further research is highlighted.

A typology of North Sea oil and gas platforms

Since the commercial exploitation of marine oil and gas reserves began in the middle of the twentieth century, extensive networks of offshore infrastructure have been installed globally. Many of the structures are now nearing the end of their operational lives and will soon require decommissioning, generating renewed interest in their environmental impacts and in the ecological consequences of their removal. However, such work requires selection of a subsample of assets for surveying; censuses of the entire 'population' in any given jurisdiction are practically impossible due to their sheer number. It is important, therefore, that the selected sample is sufficiently representative of the population to draw generalized conclusions. Here, a formal clustering methodology, partitioning around medoids, was used to produce a typology of surface-piercing oil and gas platforms in the North Sea. The variables used for clustering were hydrocarbon product, operational state, platform design and material, and substructure weight. Assessing intra-cluster variability identified 13 clusters as the optimum number. The most important distinguishing variable was platform type, isolating floating platforms first, then concrete gravity-based and then fixed steel. Following clustering, a geographic trend was evident, with oil production more prevalent in the north and gas in the south. The typology allows a representative subset of North Sea oil and gas platforms to be selected when designing a survey, or an assessment of the representativeness of a previously selected subset of platforms. This will facilitate the efficient use of the limited funding available for such studies.

Assessment of the Habitat Quality of Offshore Area in Tongzhou Bay, China: Using Benthic Habitat Suitability and the InVEST Model

Coastal zones, and in particular offshore areas, are coming under ever-increasing pressure from human development. Therefore, the evaluation of habitat quality is of vital importance for management of coastal zones. The InVEST model adopts a multi-module and multi-level design form, which has the advantages of strong visualization and fast calculation. As a result, this study used the InVEST-Habitat quality (HQ) model to assess the habitat quality of the Tongzhou Bay offshore area. Development activities were included in the classification of habitat types and the benthic habitat suitability index was used to describe the spatial variation in habitat quality of the offshore area. The results showed that the methodological approach mentioned above achieved a more detailed assessment of the spatial variation in habitat quality. The empirical model constructed based on the relationship between the Shannon–Weiner index and environmental factors performed well in revealing the suitability of habitat, with the regression equation showing an R2 of 0.57 and R2 of 0.5 significant at level of p < 0.05. The habitat suitability of Tongzhou Bay water was mainly influenced by aquaculture and industrial sea use. The habitat quality of Tongzhou Bay was relatively low due to disturbance by coastal development and a low water habitat suitability. The distribution of habitat quality in Tongzhou Bay was uneven and improved with the increase of the distance from the coast. Improvement of the habitat quality of Tongzhou Bay requires strict control of sea reclamation, optimization of the structure of offshore aquaculture, improvements to water quality and habitat suitability, and strengthening of the protection of areas of high habitat quality. This study provides a novel method for evaluating habitat quality of offshore areas.

Effects of pile driving sound on local movement of free-ranging Atlantic cod in the Belgian North Sea

Offshore energy acquisition through the construction of wind farms is rapidly becoming one of the major sources of green energy all over the world. The construction of offshore wind farms contributes to the ocean soundscape as steel monopile foundations are commonly hammered into the seabed to anchor wind turbines. This pile driving activity causes repeated, impulsive, low-frequency sounds, reaching far into the environment, which may have an impact on the surrounding marine life. In this study, we investigated the effect of the construction of 50 wind turbine foundations, over a time span of four months, on the presence and movement behaviour of free-swimming, individually tagged Atlantic cod. The turbine foundations were constructed at a distance ranging between 2.3 and 7.1 km from the cod, which resided in a nearby, existing wind farm in the southern North Sea. Our results indicated that local fish remained in the exposed area during and in-between pile-driving activities, but showed some modest changes in movement patterns. The tagged cod did not increase their net movement activity, but moved closer to the scour-bed (i.e. hard substrate), surrounding their nearest turbine, during and after each piling event. Additionally, fish moved further away from the sound source, which was mainly due to the fact that they were positioned closer to a piling event before its start. We found no effect of the time since the last piling event. Long-term changes in movement behaviour can result in energy budget changes, and thereby in individual growth and maturation, eventually determining growth rate of populations. Consequently, although behavioural changes to pile driving in the current study seem modest, we believe that the potential for cumulative effects, and species-specific variation in impact, warrant more tagging studies in the future, with an emphasis on quantification of energy budgets.

Biofouling on an Offshore Rig in the Baltic Sea

Biofouling is called “lessons from nature”. Currently, governments and industry spend more than 5.7 billion USD annually to control unwanted marine biofouling, aquatic flora and fauna on submerged construction leading to various technical, economical, and ecological problems. In turn, the Baltic Sea is defined as a “time machine” for the future coastal ocean, as processes occurring in the Baltic Sea are related to future changes. Our study describes the biofouling community at 12 sites located at different depths on the legs of the “Baltic Beta” oil platform that resulted in finding a maximum of 1,300 individuals on 400 cm2. We analyzed: spatial distribution of dominant marine organisms living on a steel platform surface, their abundance and mass. Our work showed no significant difference in the benthic samples mass among different depths or cardinal directions of the rig columns. Our research can help to predict offshore biofouling on other devices in the Baltic Sea, to control invasive species and to estimate environmental load.

Spatial and temporal analysis of cumulative environmental effects of offshore wind farms in the North Sea basin

The North Sea basin is one of the busiest maritime areas globally with a considerable number of anthropogenic pressures impacting the functioning of the marine ecosystem. Due to growing EU ambitions for the deployment of large offshore wind farm projects (OWF), as part of the 2050 renewable energy roadmap, there is a key need for a holistic understanding of OWF potential impacts on the marine ecosystem. We propose a holistic Cumulative Effect Assessment methodology, applied using a geo-spatial open-source software, to assess impacts of OWF related pressures on selected seabed habitats, fish, seabird and mammal species. We take into account pressures specific to the three OWF development phases, spanning 1999-2050, for the entire North Sea basin. Our results underline 2022 as the peak year of cumulative impacts for the approved OWFs, followed by a considerable increase in potential impacts of the planned 212GWs, by 2050. The spatio-temporal analysis of the OWF environmental impacts presents the shift between highly impacted areas over the studied timeline and distinguishes between concentrated areas of high impacts (S-E of UK) and dispersed areas of high impacts (Germany). Our results can inform decision-makers and the OWF industry in a joint effort to mitigate the environmental impacts of future large OWF developments.

Offshore multi-purpose platforms for a Blue Growth: A technological, environmental and socio-economic review

"Blue Growth" and "Blue Economy" is defined by the World Bank as: "the sustainable use of ocean resources for economic growth, improved livelihoods and jobs, while preserving the health of ocean ecosystem". Multi-purpose platforms (MPPs) can be defined as offshore platforms serving the needs of multiple offshore industries (energy and aquaculture), aim at exploiting the synergies and managing the tensions arising when closely co-locating systems from these industries. Despite a number of previous projects aimed at assessing, from a multidisciplinary point of view, the feasibility of multipurpose platforms, it is here shown that the state-of-the-art has focused mainly on single-purpose devices, and adopting a single discipline (either economic, or social, or technological, or environmental) approach. Therefore, the aim of the present study is to provide a multidisciplinary state of the art review on, whenever possible, multi-purpose platforms, complementing it with single-purpose and/or single discipline literature reviews when not possible. Synoptic tables are provided, giving an overview of the multi-purpose platform concepts investigated, the numerical approaches adopted, and a comprehensive snapshot classifying the references discussed by industry (offshore renewables, aquaculture, both) and by aspect (technological, environmental, socio-economic). The majority of the multi-purpose platform concepts proposed are integrating only multiple offshore renewable energy devices (e.g. hybrid wind-wave), with only few integrating also aquaculture systems. MPPs have significant potential in economizing CAPEX and operational costs for the offshore energy and aquaculture industry by means of concerted spatial planning and sharing of infrastructure.

Using Artificial-Reef Knowledge to Enhance the Ecological Function of Offshore Wind Turbine Foundations: Implications for Fish Abundance and Diversity

As the development of large-scale offshore wind farms (OWFs) amplifies due to technological progress and a growing demand for renewable energy, associated footprints on the seabed are becoming increasingly common within soft-bottom environments. A large part of the footprint is the scour protection, often consisting of rocks that are positioned on the seabed to prevent erosion. As such, scour protection may resemble a marine rocky reef and could have important ecosystem functions. While acknowledging that OWFs disrupt the marine environment, the aim of this systematic review was to examine the effects of scour protection on fish assemblages, relate them to the effects of designated artificial reefs (ARs) and, ultimately, reveal how future scour protection may be tailored to support abundance and diversity of marine species. The results revealed frequent increases in abundances of species associated with hard substrata after the establishment of artificial structures (i.e., both OWFs and ARs) in the marine environment. Literature indicated that scour protection meets the requirements to function as an AR, often providing shelter, nursery, reproduction, and/or feeding opportunities. Using knowledge from AR models, this review suggests methodology for ecological improvements of future scour protections, aiming towards a more successful integration into the marine environment.

Influence of environmental factors on macrofoulant assemblages on moored buoys in the eastern Arabian Sea

Factors governing the distribution of organisms in the pelagic ocean are understudied. In this paper we describe environmental parameters and macrofouling assemblages on 11 buoys deployed in the Arabian Sea for an average duration of 322 days. Macrofoulants on all the mooring components extending from the sea-surface to a depth of 1800–4300 m were documented. Role of temperature, salinity, dissolved oxygen, biological productivity and zooplankton community in governing the macrofoulant distribution are described. Species composition, vertical zonation and wet biomass exhibited significant spatial variations. Lepas anatifera constituted more than 90% of foulant wet biomass on all moorings. Assemblages in the southeastern (SEAS), east-central (ECAS) and northeast (NEAS) regions were distinct. Density of L. anatifera on surface buoys were low in SEAS (0.2±0.09 no./cm²), high in ECAS (0.32±0.11 no./cm²) and moderate in NEAS (0.23±0.04no./cm²). Macrofoulants were observed up to a depth of 75 m in SEAS, 130 m in ECAS and 120 m in NEAS. The depth profile of macrofoulant assemblages on moorings could be related to the prevalent hypoxic condition. Vertical profiles of wet biomass on all moorings exhibited subsurface maxima at depth ranging from 10 to 20 m, consequent to the abundance of L. anatifera in a thermally stable depth of water column, wherein diurnal and semidiurnal temperature variability was minimal. We attribute the observed variation in fouling assemblages to dissolved oxygen levels, salinity and diurnal variability in temperature and salinity.

How 'Blue' Is 'Green' Energy?

Often perceived as environmentally benign, 'green' renewable energy technologies have ecological costs that are often overlooked, especially those occurring below the waterline. After briefly discussing the impacts of hydropower on freshwater and marine organisms, we focus this review on the impacts of marine renewable energy devices (MREDs) on underwater marine organisms, particularly offshore wind farms and marine energy converters (e.g., tidal turbines). We consider both cumulative impacts and synergistic interactions with other anthropogenic pressures, using offshore wind farms and the Taiwanese white dolphin (Sousa chinensis taiwanensis) as an example. While MREDs undoubtedly can help mitigate climate change, variability in the sensitivity of different species and ecosystems means that rigorous case-by-case assessments are needed to fully comprehend the consequences of MRED use.

Effect of low frequency electromagnetic field on the behavior and bioenergetics of the polychaete Hediste diversicolor

The aim of the present study was to determine the effect of an electromagnetic field (EMF) of value typically recorded in the vicinity of submarine cables (50 Hz, 1 mT) on the behavior and bioenergetics of the polychaete Hediste diversicolor. No avoidance or attraction behavior to EMF was shown, but the burrowing activity of H. diversicolor was enhanced in EMF treatment, indicating a stimulating effect on bioturbation potential. The polychaete maintained a positive energy balance and high amount (85% of assimilated energy) of energy available for individual production (scope for growth) after exposure to EMF. Food consumption and respiration rates were not affected but ammonia excretion rate was significantly reduced in EMF-exposed animals compared to the control conditions (geomagnetic field). The mechanisms behind this effect remain, however, unclear. This is the first study demonstrating the effects of environmentally realistic EMF value on the behavior and physiology of marine invertebrates, thus there is a need for more research.

Genotoxic and cytotoxic effects of 50 Hz 1 mT electromagnetic field on larval rainbow trout (Oncorhynchus mykiss), Baltic clam (Limecola balthica) and common ragworm (Hediste diversicolor)

The aim of this research was to assess genotoxicity and cytotoxicity responses in aquatic animals exposed to 50 Hz 1 m T electromagnetic field (EMF). Rainbow trout (Oncorhynchus mykiss) at early stages of development were exposed to EMF for 40 days, whereas marine benthic invertebrates - the common ragworm Hediste diversicolor and the Baltic clam Limecola balthica - for 12 days. To define genotoxicity and cytotoxicity responses in selected animals, assays of nuclear abnormalities in peripheral blood erythrocytes of O. mykiss, coelomocytes of H. diversicolor and gill cells of L. balthica were performed. Induction of formation of micronuclei (MN), nuclear buds (NB), nuclear buds on filament cells (NBf) and cells with blebbed nuclei (BL) were assessed as genotoxicity endpoints, and 8-shaped nuclei, fragmented (Fr), apoptotic (Ap) and binucleated (BN) cells as cytotoxicity endpoints. Exposure to EMF affected all studied species but with varying degrees. The strongest responses to EMF treatment were elicited in L. balthica, in which six out of the total eight analyzed geno- and cytotoxicity endpoints were significantly elevated. Significantly induced frequencies of MN were detected in O. mykiss and H. diversicolor cells, NBf and BL only in gill cells of L. balthica, and NB in analyzed tissues of all the test species. As cytotoxicity endpoints, a significant elevation in frequencies of cells with 8-shaped nuclei was found in O. mykiss and L. balthica, while Ap and BN was observed only in L. balthica. EMF exposure did not induce any significant cytotoxic activity in H. diversicolor coelomocytes. The present study is the first to reveal the genotoxic and cytotoxic activity of 1 m T EMF in aquatic animals, and, consequently, the first one to report the adverse effect of this factor on common marine invertebrates and early life stages of fish.

Site Selection of Hybrid Offshore Wind and Wave Energy Systems in Greece Incorporating Environmental Impact Assessment

This paper presents a methodological framework for evaluating marine areas in Greece for the purpose of identifying the most adequate sites for Hybrid Offshore Wind and Wave Energy Systems (HOWiWaES), with special focus on the HOWiWaES’ environmental impact assessment evaluation. Nine evaluation criteria that reflect various environmental, economic, technical and socio-political aspects are considered, including Wind Velocity (WV), Wave Energy Potential (WEP), Water Depth (WD), Distance from Shore (DS), Connection to Local Electrical Grid (CLEG), Population Served (PS), Shipping Density (SD), Distance from Ports (DP) and Environmental Performance Value (EPV). Analytical Hierarchy Process (AHP) is performed to hierarchically rank twelve predefined siting alternatives. Questionnaires are used to collect information on pairwise comparisons of the evaluation criteria from a group of stakeholders/experts. Geographic Information Systems (GIS) are used as a metric tool for pairwise comparisons of each siting alternative with respect to the first eight evaluation criteria, while the last criterion is assessed through the development of an innovative environmental impact assessment tool. The results indicate that WV, WEP and EPV present the evaluation criteria with the highest relative significance, while PS, DP and SD correspond to less influencing criteria. The proposed methodology can be easily applied to other countries worldwide for supporting socially accepted siting of HOWiWaES.

Ship breaking or scuttling? A review of environmental, economic and forensic issues for decision support

In a globalized world, the world trade fleet plays a pivotal role in limiting transport costs. But, the management of obsolete ships is an acute problem, with most Ship Recycling Facilities (SRF) situated in developing countries. They are renowned for their controversial work and safety conditions and their environmental impact. Paradoxically, dismantlement is paid for by the shipowners in accordance with international conventions therefore it is more profitable for them to sell off ships destined for scrapping. Scuttling, the alternative to scrapping, is assessed in the present review to compare the cost/benefit ratios of the two approaches. Although scrapping provides employment and raw materials - but with environmental, health and safety costs - scuttling provides fisheries and diving tourism opportunities but needs appropriate management to avoid organic and metal pollution, introduction of invasive species and exacerbation of coastal erosion. It is also limited by appropriate bottom depth, ship type and number. The present review inventories the environmental, health, safety, economic, and forensic aspects of each alternative.

Changes in fish communities on a small spatial scale, an effect of increased habitat complexity by an offshore wind farm

The number of offshore wind farms (OWF) is increasing to meet the demands for renewable energy. The piles and hard substrate surrounding these piles creates new habitat for species with preference to hard substrates. We studied the impact of this hard substrate on the fish community in a Dutch OWF in the sandy southern North Sea, which had been in operation for five years. Multi-mesh gillnets were placed near the OWF structures on the hard substrate protection revetments and on the sandy bottom in the middle of the farm. The catches indicated attraction of cod, pouting, bullrout and edible and velvet crab, while attraction to the sandy habitat was shown for flatfish and whiting. Further, two species previously not caught in this area, goldsinny wrasse and grey trigger fish, were caught on the hard substrate. In addition a Dual-Frequency Identification Sonar (DIDSON) was used to record transects through the farm to observe individual fish in the water column throughout the farm and very near the OWF structures. High abundances of fish near the structure were observed during some days, while during other days equal distribution of fish in the area was observed. The area around the structures is thus only used temporarily for shelter or feeding. The DIDSON also allowed looking at the aggregation level of the fish. Seasonally the aggregation level differed most likely due to different species occurring in the area. In April, most fish were aggregated in schools, while in summer most observations were individual fish or loose aggregations. The wind farm structures had limited effect on the aggregation level compared to season or weather conditions.

Effects of an Offshore Wind Farm (OWF) on the Common Shore Crab Carcinus maenas: Tagging Pilot Experiments in the Lillgrund Offshore Wind Farm (Sweden)

Worldwide growth of offshore renewable energy production will provide marine organisms with new hard substrate for colonization in terms of artificial reefs. The artificial reef effect is important when planning offshore installations since it can create habitat enhancement. Wind power is the most advanced technology within offshore renewable energy sources and there is an urgent need to study its impacts on the marine environment. To test the hypothesis that offshore wind power increases the abundance of reef species relative to a reference area, we conduct an experiment on the model species common shore crab (Carcinus maenas).Overall, 3962 crabs were captured, observed, marked and released in 2011 and 1995 crabs in 2012. Additionally, carapace size, sex distribution, color morphs and body condition was recorded from captured crabs. We observed very low recapture rates at all sites during both years which made evaluating differences in population sizes very difficult. However, we were able to estimate population densities from the capture record for all three sites. There was no obvious artificial reef effect in the Lillgrund wind farm, but a spill-over effect to nearby habitats cannot be excluded. We could not find any effect of the wind farm on either, morphs, sex distribution or condition of the common shore crab. Our study found no evidence that Lillgrund wind farm has a negative effect on populations of the common shore crab. This study provides the first quantitative and experimental data on the common shore crab in relation to offshore wind farms.

Mitigation Measures for Wildlife in Wind Energy Development, Consolidating the State of Knowledge — Part 2: Operation, Decommissioning

During this rapid development of wind energy aiming to combat climate change worldwide, there is greater need to avoid, reduce, and compensate for impacts on wildlife: Through the effective use of mitigation, wind energy can continue to expand while reducing impacts. This is a first broad step into discussing and understanding mitigation strategies collectively, identifying the current state of knowledge and be a beneficial resource for practitioners and conservationists.

We review the current state of published knowledge, both land-based and offshore, with a focus on wind energy–wildlife mitigation measures. We state measures and highlight their objective and discuss at which project stage it is most effective (e.g. planning, construction, operation). Thereafter, we discuss key findings within current wind energy mitigation research, needing improved understanding into the efficacy of wildlife mitigation as well as research into the cost aspects of mitigation implementation. This review is divided into two articles; Part 1 focuses on mitigation measures during planning, siting, and construction, while Part 2 focuses on measures during operation and decommissioning.

Using insights from animal behaviour and behavioural ecology to inform marine conservation initiatives

The impacts of human activities on the natural world are becoming increasingly apparent, with rapid development and exploitation occurring at the expense of habitat quality and biodiversity. Declines are especially concerning in the oceans, which hold intrinsic value due to their biological uniqueness as well as their substantial sociological and economic importance. Here, we review the literature and investigate whether incorporation of knowledge from the fields of animal behaviour and behavioural ecology may improve the effectiveness of conservation initiatives in marine systems. In particular, we consider (1) how knowledge of larval behaviour and ecology may be used to inform the design of marine protected areas, (2) how protecting species that hold specific ecological niches may be of particular importance for maximizing the preservation of biodiversity, (3) how current harvesting techniques may be inadvertently skewing the behavioural phenotypes of stock populations and whether changes to current practices may lessen this skew and reinforce population persistence, and (4) how understanding the behavioural and physiological responses of species to a changing environment may provide essential insights into areas of particular vulnerability for prioritized conservation attention. The complex nature of conservation programmes inherently results in interdisciplinary responses, and the incorporation of knowledge from the fields of animal behaviour and behavioural ecology may increase our ability to stem the loss of biodiversity in marine environments.

Potential Impacts of Offshore Wind Farms on North Sea Stratification

Advances in offshore wind farm (OWF) technology have recently led to their construction in coastal waters that are deep enough to be seasonally stratified. As tidal currents move past the OWF foundation structures they generate a turbulent wake that will contribute to a mixing of the stratified water column. In this study we show that the mixing generated in this way may have a significant impact on the large-scale stratification of the German Bight region of the North Sea. This region is chosen as the focus of this study since the planning of OWFs is particularly widespread. Using a combination of idealised modelling and in situ measurements, we provide order-of-magnitude estimates of two important time scales that are key to understanding the impacts of OWFs: (i) a mixing time scale, describing how long a complete mixing of the stratification takes, and (ii) an advective time scale, quantifying for how long a water parcel is expected to undergo enhanced wind farm mixing. The results are especially sensitive to both the drag coefficient and type of foundation structure, as well as the evolution of the pycnocline under enhanced mixing conditions-both of which are not well known. With these limitations in mind, the results show that OWFs could impact the large-scale stratification, but only when they occupy extensive shelf regions. They are expected to have very little impact on large-scale stratification at the current capacity in the North Sea, but the impact could be significant in future large-scale development scenarios.

Biofouling community composition across a range of environmental conditions and geographical locations suitable for floating marine renewable energy generation

Knowledge of biofouling typical of marine structures is essential for engineers to define appropriate loading criteria in addition to informing other stakeholders about the ecological implications of creating novel artificial environments. There is a lack of information regarding biofouling community composition (including weight and density characteristics) on floating structures associated with future marine renewable energy generation technologies. A network of navigation buoys were identified across a range of geographical areas, environmental conditions (tidal flow speed, temperature and salinity), and deployment durations suitable for future developments. Despite the perceived importance of environmental and temporal factors, geographical location explained the greatest proportion of the observed variation in community composition, emphasising the importance of considering geography when assessing the impact of biofouling on device functioning and associated ecology. The principal taxa associated with variation in biofouling community composition were mussels (Mytilus edulis), which were also important when determining loading criteria.

Renewables-to-reefs? - Decommissioning options for the offshore wind power industry

The offshore wind power industry is relatively new but increasing globally, hence it is important that the whole life-cycle is managed. The construction-operation-decommissioning cycle is likely to take 20-30 years and whilst decommissioning may not be undertaken for many years, its management needs to be addressed in both current and future marine management regimes. This can be defined within a Drivers-Activities-Pressures-State Changes-Impacts (on human Welfare)-Responses framework. This paper considers the main decommissioning options - partial or complete removal of all components. A SWOT analysis shows environmental and economic benefits in partial as opposed to complete removal, especially if habitat created on the structures has conservation or commercial value. Benefits (and repercussions) are defined in terms of losses and gains of ecosystem services and societal benefits. The legal precedents and repercussions of both options are considered in terms of the 10-tenets of sustainable marine management. Finally a 'renewables-to-reefs' programme is proposed.

Applicability of the "Frame of Reference" approach for environmental monitoring of offshore renewable energy projects

This paper assesses the applicability of the Frame of Reference (FoR) approach for the environmental monitoring of large-scale offshore Marine Renewable Energy (MRE) projects. The focus is on projects harvesting energy from winds, waves and currents. Environmental concerns induced by MRE projects are reported based on a classification scheme identifying stressors, receptors, effects and impacts. Although the potential effects of stressors on most receptors are identified, there are large knowledge gaps regarding the corresponding (positive and negative) impacts. In that context, the development of offshore MRE requires the implementation of fit-for-purpose monitoring activities aimed at environmental protection and knowledge development. Taking European legislation as an example, it is suggested to adopt standardized monitoring protocols for the enhanced usage and utility of environmental indicators. Towards this objective, the use of the FoR approach is advocated since it provides guidance for the definition and use of coherent set of environmental state indicators. After a description of this framework, various examples of applications are provided considering a virtual MRE project located in European waters. Finally, some conclusions and recommendations are provided for the successful implementation of the FoR approach and for future studies.

Spatial and temporal benthic species assemblage responses with a deployed marine tidal energy device: a small scaled study

The addition of man-made structures to the marine environment is known to increase the physical complexity of the seafloor, which can influence benthic species community patterns and habitat structure. However, knowledge of how deployed tidal energy device structures influence benthic communities is currently lacking. Here we examined species biodiversity, composition and habitat type surrounding a tidal energy device within the European Marine Energy Centre test site, Orkney. Commercial fishing and towed video camera techniques were used over three temporal periods, from 2009 to 2010. Our results showed increased species biodiversity and compositional differences within the device site, compared to a control site. Both sites largely comprised of crustacean species, omnivore or predatory feeding regimes and marine tide-swept EUNIS habitat types, which varied over the time. We conclude that the device could act as a localised artificial reef structure, but that further in-depth investigations are required.

Enrichment and shifts in macrobenthic assemblages in an offshore wind farm area in the Belgian part of the North Sea

The growing development of offshore wind energy installations across the North Sea is producing new hard anthropogenic structures in the natural soft sediments, causing changes to the surrounding macrobenthos. The extent of modification in permeable sediments around a gravity based wind turbine in the Belgian part of the North Sea was investigated in the period 2011-2012, along four gradients (south-west, north-east, south-east, north-west). Sediment grain size significantly reduced from 427 μm at 200 m to 312 ± 3 μm at 15 m from the foundation along the south-west and north-west gradients. The organic matter content increased from 0.4 ± 0.01% at 100 m to 2.5 ± 0.9% at 15 m from the foundation. The observed changes in environmental characteristics triggered an increase in the macrobenthic density from 1390 ± 129 ind m⁻² at 200 m to 18 583 ± 6713 ind m⁻² at 15 m together with an enhanced diversity from 10 ± 2 at 200 m to 30 ± 5 species per sample at 15 m. Shifts in species dominance were also detected with a greater dominance of the ecosystem-engineer Lanice conchilega (16-25%) close to the foundation. This study suggests a viable prediction of the effects offshore wind farms could create to the naturally occurring macrobenthos on a large-scale.

Impact of secondary hard substrate on the distribution and abundance of Aurelia aurita in the western Baltic Sea

This study assessed the impact of secondary hard substrate, as being introduced into marine ecosystems by the establishment of wind farm pillars, on the occurrence and distribution of the moon jelly Aurelia aurita in the southwestern Baltic Sea. A two-year data sampling was conducted with removable settlement plates to assess the distribution and population development of the scyphozoan polyps. The data collected from these samples were used to set up a model with Lagrangian particle technique. The results confirm that anthropogenic created hard substrate (e.g. offshore wind farms) has the potential to increase the abundance of the A. aurita population. The distribution of wind farm borne jellyfish along Danish, German and Polish coasts indicates conflicts with further sectors, mainly energy and tourism.

Residency, site fidelity and habitat use of Atlantic cod (Gadus morhua) at an offshore wind farm using acoustic telemetry

Because offshore wind energy development is fast growing in Europe it is important to investigate the changes in the marine environment and how these may influence local biodiversity and ecosystem functioning. One of the species affected by these ecosystem changes is Atlantic cod (Gadus morhua), a heavily exploited, commercially important fish species. In this research we investigated the residency, site fidelity and habitat use of Atlantic cod on a temporal scale at windmill artificial reefs in the Belgian part of the North Sea. Acoustic telemetry was used and the Vemco VR2W position system was deployed to quantify the movement behaviour. In total, 22 Atlantic cod were tagged and monitored for up to one year. Many fish were present near the artificial reefs during summer and autumn, and demonstrated strong residency and high individual detection rates. When present within the study area, Atlantic cod also showed distinct habitat selectivity. We identified aggregation near the artificial hard substrates of the wind turbines. In addition, a clear seasonal pattern in presence was observed. The high number of fish present in summer and autumn alternated with a period of very low densities during the winter period.

Epibenthic assessment of a renewable tidal energy site

Concern over global climate change as a result of fossil fuel use has resulted in energy production from renewable sources. Marine renewable energy devices provide clean electricity but can also cause physical disturbance to the local environment. There is a considerable paucity of ecological data at potential marine renewable energy sites that is needed to assess potential future impacts and allow optimal siting of devices. Here, we provide a baseline benthic survey for the Big Russel in Guernsey, UK, a potential site for tidal energy development. To assess the suitability of proposed sites for marine renewable energy in the Big Russel and to identify potential control sites, we compared species assemblages and habitat types. This baseline survey can be used to select control habitats to compare and monitor the benthic communities after installation of the device and contribute towards the optimal siting of any future installation.

Artificial reef effect in relation to offshore renewable energy conversion: state of the art

The rapid worldwide growth of offshore renewable energy production will provide marine organisms with new hard substrate for colonization, thus acting as artificial reefs. The artificial reef effect is important when constructing, for example, scour protections since it can generate an enhanced habitat. Specifically, artificial structures can create increased heterogeneity in the area important for species diversity and density. Offshore energy installations also have the positive side effect as they are a sanctuary area for trawled organisms. Higher survival of fish and bigger fish is an expected outcome that can contribute to a spillover to outer areas. One negative side effect is that invasive species can find new habitats in artificial reefs and thus influence the native habitats and their associated environment negatively. Different scour protections in offshore wind farms can create new habitats compensating for habitat loss by offshore energy installations. These created habitats differ from the lost habitat in species composition substantially. A positive reef effect is dependent on the nature and the location of the reef and the characteristics of the native populations. An increase in surface area of scour protections by using specially designed material can also support the reef effect and its productivity.

Assessing wave energy effects on biodiversity: the wave hub experience

Marine renewable energy installations harnessing energy from wind, wave and tidal resources are likely to become a large part of the future energy mix worldwide. The potential to gather energy from waves has recently seen increasing interest, with pilot developments in several nations. Although technology to harness wave energy lags behind that of wind and tidal generation, it has the potential to contribute significantly to energy production. As wave energy technology matures and becomes more widespread, it is likely to result in further transformation of our coastal seas. Such changes are accompanied by uncertainty regarding their impacts on biodiversity. To date, impacts have not been assessed, as wave energy converters have yet to be fully developed. Therefore, there is a pressing need to build a framework of understanding regarding the potential impacts of these technologies, underpinned by methodologies that are transferable and scalable across sites to facilitate formal meta-analysis. We first review the potential positive and negative effects of wave energy generation, and then, with specific reference to our work at the Wave Hub (a wave energy test site in southwest England, UK), we set out the methodological approaches needed to assess possible effects of wave energy on biodiversity. We highlight the need for national and international research clusters to accelerate the implementation of wave energy, within a coherent understanding of potential effects-both positive and negative.

Colonisation of fish and crabs of wave energy foundations and the effects of manufactured holes - a field experiment

Several Western European countries are planning for a significant development of offshore renewable energy along the European Atlantic Ocean coast, including many thousands of wave energy devices and wind turbines. There is an increasing interest in articulating the added values of the creation of artificial hard bottom habitats through the construction of offshore renewable energy devices, for the benefit of fisheries management and conservation. The Lysekil Project is a test park for wave power located about 100 km north of Gothenburg at the Swedish west coast. A wave energy device consists of a linear wave power generator attached to a foundation on the seabed, and connected by a wire to a buoy at the surface. Our field experiment examined the function of wave energy foundations as artificial reefs. In addition, potentials for enhancing the abundance of associated fish and crustaceans through manufactured holes of the foundations were also investigated. Assemblages of mobile organisms were examined by visual censuses in July and August 2007, 3 months after deployment of the foundations. Results generally show low densities of mobile organisms, but a significantly higher abundance of fish and crabs on the foundations compared to surrounding soft bottoms. Further, while fish numbers were not influenced by increased habitat complexity (holes), it had a significantly positive effect on quantities of edible crab (Cancer pagurus), on average leading to an almost five-fold increase in densities of this species. Densities of spiny starfish (Marthasterias glacialis) were negatively affected by the presence of holes, potentially due to increased predator abundance (e.g. C. pagurus). These results suggest a species-specific response to enhanced habitat complexity.