Overview

The fifth webinar in the “Learning as We Go” series, an ongoing forum for information exchange on offshore renewable energy topics, focused on noise and electromagnetic field (EMF) impacts on benthic communities in the environment of wind farms. Presentations and dialogue explained the science of noise and EMF in the ocean environment and turbine areas, shared data concerning impacts on marine life, described mitigation techniques, and pointed to the need for continued learning via science and policy. This fifth webinar served as part of the annual Ronald C. Baird Sea Grant Science Symposium.

Welcomes were provided by Avi Mallinger, Associate Director of Strategy + Impact at Innovation Studio, host organization for the webinar series, and by program organizer Jennifer McCann, Director of U.S. Coastal Programs at the University of Rhode Island (URI) Coastal Resources Center, and Director of Extension for Rhode Island Sea Grant. McCann said the webinar series is helping answer the collective question of “what do we need to know?” with regards to offshore renewable energy topics, and indicated the material is assisting with real-life situations, such as farm siting discussions for the Gulf of Maine.

McCann then introduced a slate of participants with specific roles for the webinar: Monique LaFrance Bartley, PhD and Marine Ecologist at National Park Service, served as a co-moderator, as did Sherryll Huber Jones, the New York State Ocean Coordinator for the New York State Department of Environmental Conservation Division of Marine Resources. Presenters were Peter Sigray, Researcher at the Royal Institute of Technology (KTH) in Stockholm, Sweden; Louise Roberts, Postdoctoral Research Associate in the College of Agriculture and Life Sciences at Cornell University; and Zoë Hutchison, Postdoctoral Research Fellow at the URI Graduate School of Oceanography.

Presentations

The researchers split the discussion; Sigray provided overviews on how noise and EMF are produced in the marine environment in the context of wind turbine infrastructure, and he also reviewed some common techniques for mitigating noise and EMFs at various stages of farm activity, i.e., building, operation, and decommissioning. Roberts spoke to how noise (sound and seabed vibration) may impact marine life, and Hutchinson shared information on the topic of EMF effects on marine life, and encouraged the audience to think about how interdisciplinary collaboration and a broadening of the stakeholder circle could be an opportunity to answer many more questions about energy emissions in ocean environments.

Sigray initiated the presentation with a reminder about farm size; while older farms and projects like the Block Island Wind Farm are on the smaller end of the spectrum, the farms of the future are generally projected to be larger, with significant numbers of turbines and larger turbines. That means that the potential for development impacts – including those associated with noise and EMF – stand to increase as well. And specifically, the construction stage, when pile-type turbines are hammered into the seabed, represents the greatest potential for acute noise impacts. Sound pressure is measured as standard, however it is now widely recognized that particle motion is the more important stimulus for most fish and invertebrate species. Seabed vibrations are rarely measured or considered in impact assessments, yet there is evidence that benthic species detect these (as covered by Roberts). Variability of impact is diverse and may influence animals, from worms, to mollusks, to fish and whales, which receive, process, and experience sound differently (aspects explored by Roberts). There are ways to deal with piledriving noise, including deploying bubble curtains, which contain or absorb the sounds generated – especially effective are curtains kept in place around the pile by an encircling sheath.

Sigray then explained how EMF works; in general, wind farm turbines send power via cable systems usually buried in the seafloor and produce EMFs which may interact with the earth’s own natural magnetic fields. How a cable system is built and the degree to which it is buried in the seafloor are two of the determinants for the degree to which EMF is emitted into the ocean environment, but burial does not eliminate the EMF. We have measured AC and DC fields from buried cables. Again, the level to which EMF may impact ocean life depends on the kinds and numbers of animals around it. “It’s complicated,” Sigray said, but there is good news, he indicated: cables can be engineered to work with the issue.

Roberts then spoke to the impacts of noise on ocean life. She began by explaining that the ocean is, in fact, not a quiet place – under the water, even without manmade intrusion, there are sound and vibroscapes of sound and seabed vibration generated by the varied kinds of animals living there and abiotic sources such as currents and wind. How impactful a man-made noise is depends on the physical characteristics of the sound itself (e.g. source type, duration, pressure and particle motion, frequency content) but also biological aspects of the receiver such as hearing sensitivity, mobility of the species, habitat requirements, life cycle and even motivational state. Many underwater noise studies have been undertaken within laboratory tanks with erratic sound fields, and also do not measure particle motion, which is the detectable stimulus for fish and invertebrates, said Roberts. Additionally, seabed vibrations, produced by any source contacting the seabed, have been overlooked to date yet there is mounting evidence that these are relevant to benthic animals. Whilst we understand general impacts of manmade sounds, there are few experimental studies specifically relating to the phases of an offshore wind-farm life cycle, although for species with known hearing abilities it is possible to estimate the zone of audibility around a turbine, and there are data regarding the impacts of high amplitude sources such as pile driving, for example. “We need more information,” Roberts said, adding that emphasis should be upon experiments with noise sources measured in terms of pressure, water-borne and substrate-borne (seabed) particle motion, and studies based in field conditions rather than in laboratories. Roberts said that it is also important to recognize ocean developments as being “multi-modal, consisting of multiple simultaneous stressors of noise, light, EMF and chemical pollutants,” so we need comprehensive approaches considering multiple stimuli.

Hutchison elaborated on what is known about EMF and benthic communities further, explaining that science has a ways to go in terms of understanding, with nuance, how ocean development, including EMFs from offshore renewable energy activities. Impacts on marine animals are important to understand in the context of the ecosystem, whether the connection be economically, environmentally, or socially based. Hutchison said scientists are using all kinds of learning arenas to understand the effects of EMFs, from natural environments, to mesocosms, to aquariums to investigate a wide variety of species’ responses to EMF in the ocean – and it’s a significant start. However, Hutchison said, the work is a beginning, but it is a “patchwork” now requiring research and contribution to better understand the EMF as it is presented to species and their responses to it Also, understanding these effects, and finding ways to mitigate potential impacts will take place more effectively and efficiently if the stakeholder circle is broadened, and if innovation continues to spur the process. “Multi-disciplinary approaches to addressing the data gaps is needed,” she said.

Following the presentations, LaFrance Bartley and Huber Jones asked the presenters several questions; some were their own, others were extracted from chat room dialogue. The questions largely focused on exploring further how specific turbine activities or stages, like construction and operation, have been determined to impact certain ocean animal species. The researchers identified specific studies that represent the start to understanding impacts further, and they emphasized again the need for more study.

After the questions, McCann thanked all attendees, and told them the webinar program will commence again in 2021, and that people should indicate via a distributed survey the topics they would like to see as part of the “Learning as We Go” series.