Offshore wind energy development: Research priorities for sound and vibration effects on fishes and aquatic invertebrates

Offshore windfarm construction elevates metabolic rate and increases predation vulnerability of a key marine invertebrate

A global increase in offshore windfarm development is critical to our renewable energy future. Yet, widespread construction plans have generated substantial concern for impacts to co-occurring organisms and the communities they form. Pile driving construction, prominent in offshore windfarm development, produces among the highest amplitude sounds in the ocean creating widespread concern for a diverse array of taxa. However, studies addressing ecologically key species are generally lacking and most research is disparate, failing to integrate across response types (e.g., behavior, physiology, and ecological interactions), particularly in situ. The lack of integrative field studies presents major challenges to understand or mitigate actual impacts of offshore wind development. Here, we examined critical behavioral, physiological, and antipredator impacts of actual pile driving construction on the giant sea scallop (Placopecten magellanicus). Benthic taxa including bivalves are of particular concern because they are sound-sensitive, cannot move appreciable distances away from the stressor, and support livelihoods as one of the world's most economically and socially important fisheries. Overall, pile driving sound impacted scallops across a series of behavioral and physiological assays. Sound-exposed scallops consistently reduced their valve opening (22%), resulting in lowered mantle water oxygen levels available to the gills. Repeated and rapid valve adductions led to a 56% increase in metabolic rates relative to pre-exposure baselines. Consequently, in response to predator stimuli, sound-exposed scallops displayed a suite of significantly weaker antipredator behaviors including fewer swimming events and shorter time-to-exhaustion. These results show aquatic construction activities can induce metabolic and ecologically relevant changes in a key benthic animal. As offshore windfarm construction accelerates globally, our field-based study highlights that spatial overlap with benthic taxa may cause substantial metabolic changes, alter important fisheries resources, and ultimately could lead to increased predation.

Transcriptomic analysis of the response mechanisms of black rockfish (Sebastes schlegelii) under noise stress from offshore wind farms

During the operational phase of offshore wind farms, the generation of low-frequency underwater noise has received widespread attention due to its potential adverse impact on fish health. This study conducted a field survey of underwater noise at offshore wind farms located in Shandong province, China. Subsequently, a small-scale experiment was conducted to study the stress on black rockfish (Sebastes schlegelii). The fish were exposed to noise with dominant frequency of 80 Hz, 125 Hz and 250 Hz. These frequencies are same with the frequencies from wind power noise (wpn) at the actual site. After a 40-day experimental period, transcriptome sequencing was conducted on brain, liver, and kidney tissues of black rockfish to elucidate the underlying molecular mechanisms involved in the response to noise stress originating from offshore wind farms. The results revealed that the 125 Hz group exhibited the highest number of differentially expressed genes (DEGs) between the noise-exposed and control check group (CK group), with a total of 797 in the brain, 1076 in the liver, and 2468 in the kidney. Gene Ontology (GO) analysis showed that DEGs were significantly enriched in entries related to cellular processes, membrane components, binding, and metabolism. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were enriched mainly in metabolism, immunity, apoptosis, signal transduction, and diseases. The findings indicate that prolonged exposure to underwater noise from offshore wind farms may induce metabolic imbalance, immune dysfunction, and an increased risk of myocardial diseases in black rockfish.

Impulsive pile driving sound does not induce hearing loss in the longfin squid (Doryteuthis pealeii)a)

Offshore windfarms are a key means to produce clean energy as we seek to limit climate change effects. Impulsive pile driving used for their construction in shallow water environments is among the most intense anthropogenic sound sources. There is an increasing understanding that an array of marine invertebrates detects acoustic cues, yet little is known about how pile driving sound could impact their sound detection abilities. We experimentally quantified potential changes in sound sensitivity for an abundant, commercially and ecologically important squid species (Doryteuthis pealeii) exposed to actual in situ pile driving. The pile was 0.3-m diameter and 10-m long; hammer energy reached 16 kJ per strike. Sound detection thresholds were determined using auditory evoked potentials in animals with no exposure, after one 15-min or five repeated 15-min long pile driving sound sequences, corresponding to cumulative sound exposure levels of 110 and 131 dB re (1 μm s-2)2 s for acceleration and 187 and 214 dB re (1 μPa)2 s for pressure. We found no statistical evidence of temporary threshold shifts in any squid exposed to pile driving sound sequences. These results, combined with companion behavioral studies, suggest that squid may be robust to the sound impacts during offshore windfarm construction.

Scaling laws for mitigated pile driving: Dependence of underwater noise on strike energy, pile diameter, ram weight, water depth, and mitigation systema)

Sound induced by impact pile driving is a possible risk to marine life. Therefore, it is common practice to use noise mitigation systems during piling to reduce the respective impact and to fulfill the prescribed noise limits. Scaling laws for the estimation of the underwater noise from unmitigated impact pile driving have been presented in von Pein, Lippert, Lippert, and von Estorff, "Scaling laws for unmitigated pile driving: Dependence of underwater noise on strike energy, pile diameter, ram weight, and water depth," Appl. Acoust. 198, 108986 (2022). This contribution shows how these scaling laws need to be changed if noise mitigation systems are considered. Scaling laws are developed for four different kinds of noise mitigation system setups. These include big bubble curtains, double big bubble curtain combinations, a fully absorbing system directly at the pile, and the combination of a system close to the pile and a double big bubble curtain. The derived scaling laws are verified and compared to publicly available measurement data.

Introduction to the special issue on fish bioacoustics: Hearing and sound communicationa)

Fish bioacoustics, or the study of fish hearing, sound production, and acoustic communication, was discussed as early as Aristotle. However, questions about how fishes hear were not really addressed until the early 20th century. Work on fish bioacoustics grew after World War II and considerably in the 21st century since investigators, regulators, and others realized that anthropogenic (human-generated sounds), which had primarily been of interest to workers on marine mammals, was likely to have a major impact on fishes (as well as on aquatic invertebrates). Moreover, passive acoustic monitoring of fishes, recording fish sounds in the field, has blossomed as a noninvasive technique for sampling abundance, distribution, and reproduction of various sonic fishes. The field is vital since fishes and aquatic invertebrates make up a major portion of the protein eaten by a signification portion of humans. To help better understand fish bioacoustics and engage it with issues of anthropogenic sound, this special issue of The Journal of the Acoustical Society of America (JASA) brings together papers that explore the breadth of the topic, from a historical perspective to the latest findings on the impact of anthropogenic sounds on fishes.

Comprehensive analysis of the seismic wave fields generated by offshore pile driving: A case study at the BARD Offshore 1 offshore wind farm

Offshore pile driving not only generates high sound pressure levels, but also induces ground vibrations and particle motions that have the potential to affect fish and invertebrates living near or in the seabed. In particular, the seismic wave field in the form of interface waves is thought to be responsible for causing these particle motions and ground vibrations. However, the magnitude and spatial extent of the seismic wave field resulting from pile driving has not been clearly established. To fill this knowledge gap, this paper analyzes and illustrates in detail the seismic wave field at a construction site of the BARD Offshore 1 wind farm. For this purpose, the measured data from the construction site are compared to the results of a seismo-acoustic model. The measured and modeled data in combination provides a potential benchmark case for subsequent studies and other authors. The computed seismic wave field is investigated in terms of wave generation, mode composition, and propagation range of individual modes. The different seismic wave forms and their contribution to the particle motions in the seabed vicinity are discussed. The results indicate that, for the considered case, interface waves dominate the particle motion at the seafloor level up to a distance of 200 m.

Anthropogenic underwater noise: A review on physiological and molecular responses of marine biota

The detrimental effects of anthropogenic underwater noise on marine organisms have garnered significant attention among scientists. This review delves into the research concerning the repercussions of underwater noise on marine species, with specific emphasis on the physiological and molecular responses of marine biota. This review investigates the sensory mechanisms, hearing sensitivity, and reaction thresholds of diverse marine organisms, shedding light on their susceptibility to underwater noise disturbances. The physiological and molecular effects of anthropogenic underwater noise on marine biota include oxidative stress, energy homeostasis, metabolism, immune function, and respiration. Additionally, changes in the gene expression profile associated with oxidative stress, metabolism, and immunological response are among the responses reported for marine biota. These effects pose a threat to animal fitness and potentially affect their survival as individuals and populations.

Navigating noisy waters: A review of field studies examining anthropogenic noise effects on wild fisha)

Anthropogenic noise is globally increasing in aquatic ecosystems, and there is concern that it may have adverse consequences in many fish species, yet the effects of noise in field settings are not well understood. Concern over the applicability of laboratory-conducted bioacoustic experiments has led to a call for, and a recent increase in, field-based studies, but the results have been mixed, perhaps due to the wide variety of techniques used and species studied. Previous reviews have explored the behavioral, physiological, and/or anatomical costs of fish exposed to anthropogenic noise, but few, if any, have focused on the field techniques and sound sources themselves. This review, therefore, aims to summarize, quantify, and interpret field-based literature, highlight novel approaches, and provide recommendations for future research into the effects of noise on fish.

Vibrational and acoustic communication in fishes: The overlooked overlap between the underwater vibroscape and soundscape

Substrate-borne communication via mechanical waves is widespread throughout the animal kingdom but has not been intensively studied in fishes. Families such as the salmonids and sculpins have been documented to produce vibratory signals. However, it is likely that fish taxa on or close to the substrate that produce acoustic signals will also have a vibratory component to their signal due to their proximity to substrates and energy transfer between media. Fishes present an intriguing opportunity to study vibrational communication, particularly in the context of signal production and detection, detection range, and how vibratory signals may complement or replace acoustic signals. It is highly likely that the vibrational landscape, the vibroscape, is an important component of their sensory world, which certainly includes and overlaps with the soundscape. With the wide range of anthropogenic activities modifying underwater substrates, vibrational noise presents similar risks as acoustic noise pollution for fishes that depend on vibrational communication. However, in order to understand vibrational noise, more empirical studies are required to investigate the role of vibrations in the fish environment.

Sound and sturgeon: Bioacoustics and anthropogenic sounda)

Sturgeons are basal bony fishes, most species of which are considered threatened and/or endangered. Like all fishes, sturgeons use hearing to learn about their environment and perhaps communicate with conspecifics, as in mating. Thus, anything that impacts the ability of sturgeon to hear biologically important sounds could impact fitness and survival of individuals and populations. There is growing concern that the sounds produced by human activities (anthropogenic sound), such as from shipping, commercial barge navigation on rivers, offshore windfarms, and oil and gas exploration, could impact hearing by aquatic organisms. Thus, it is critical to understand how sturgeon hear, what they hear, and how they use sound. Such data are needed to set regulatory criteria for anthropogenic sound to protect these animals. However, very little is known about sturgeon behavioral responses to sound and their use of sound. To help understand the issues related to sturgeon and anthropogenic sound, this review first examines what is known about sturgeon bioacoustics. It then considers the potential effects of anthropogenic sound on sturgeon and, finally identifies areas of research that could substantially improve knowledge of sturgeon bioacoustics and effects of anthropogenic sound. Filling these gaps will help regulators establish appropriate protection for sturgeon.

Atlantic cod (Gadus morhua) larvae are attracted by low-frequency noise simulating that of operating offshore wind farms

The number and size of offshore wind (OW) turbines is increasing rapidly. OW turbines produce continuous, low-frequency noise that could impact marine fish dispersing/migrating through the facilities. Any such impact would be relevant for larval stages, which have limited possibility to swim away from OW facilities. If directional movement of fish larvae at sea is impacted by low-frequency continuous sound is unknown. We observe the behavior of Atlantic cod larvae (N = 89) in response to low-frequency sound while they are drifting in a Norwegian fjord inside transparent drifting chambers. We transmit 100 Hz continuous sound in the fjord, in the intensity range of OW turbines' operational noise, and measure the sound pressure and 3-D particle motion. Half of the larvae (N = 45) are exposed to low-frequency (100 Hz) continuous sound, while the other half (N = 44) are observed under the same conditions but without the sound. Exposure does not affect the routine and maximum swimming speeds or the turning behavior of the larvae. Control larvae orient to the northwest. In contrast, exposed larvae orient towards the source of low-frequency sound and particle motion. This provides a basis to assess how OW might impact dispersal in this species.

Pile driving repeatedly impacts the giant scallop (Placopecten magellanicus)

Large-scale offshore wind farms are a critical component of the worldwide climate strategy. However, their developments have been opposed by the fishing industry because of concerns regarding the impacts of pile driving vibrations during constructions on commercially important marine invertebrates, including bivalves. Using field-based daily exposure, we showed that pile driving induced repeated valve closures in different scallop life stages, with particularly stronger effects for juveniles. Scallops showed no acclimatization to repetitive pile driving across and within days, yet quickly returned to their initial behavioral baselines after vibration-cessation. While vibration sensitivity was consistent, daily pile driving did not disrupt scallop circadian rhythm, but suggests serious impacts at night when valve openings are greater. Overall, our results show distance and temporal patterns can support future mitigation strategies but also highlight concerns regarding the larger impact ranges of impending widespread offshore wind farm constructions on scallop populations.