A noisy abyss: How deep seabed mining could impact whales
© Alexis Rosenfeld
Imagine trying to be heard across the vast ocean against a noise-cacophony. Baleen whales have perfected communicating across the ocean. Fin whale calls, for example, can travel up to 6,000 km in the deep sound channel. These calls are part of the natural soundscape of the underwater world. Under the ocean’s surface, whales are surrounded by sound, including vocalizations from their species, as well as other marine fauna, such as fish, crustaceans, and seals.
Navigating an ocean full of sound
Sound travels faster and farther than light in the dense medium of water. In fact, 1,000 m below the surface of the ocean, there is no light at all. As a result, whales and other marine wildlife use sound rather than light to brighten their world. Without sound, whales are blind to their watery surroundings and would have difficulty communicating, navigating, finding food, mating, or avoiding predators.
But these naturally occurring sounds, which cetaceans (whales, dolphins, and porpoises), and other marine wildlife, depend on to survive, are at risk of being drowned out by noise pollution. Noise from ships passing overhead, the sounds of seismic airguns in search of new sources of oil and gas, and construction all pollute the underwater soundscape penetrating deep into the ocean.
Professor Christine Erbe
Professor Christine Erbe is a John Curtin Distinguished Professor at the School of Earth and Planetary Sciences at Curtin University and the Director of the Centre for Marine Science and Technology. She specializes in underwater acoustics and bioacoustics, studying sound generation and propagation underwater and the effects of noise on marine fauna.
“The ocean is naturally noisy with sounds of animals, wind, precipitation, polar ice, subsea earthquakes and volcanoes, etc. But anthropogenic noise is a recent addition and has dramatically increased over the last 100 years. This needs to be managed,” says Professor Christine Erbe.
The damaging impacts of underwater noise
Responses to underwater noise vary from species to species. For instance, a study examining how narwhals react to seismic air guns used by the oil and gas industry found that when exposed, narwhals start diving immediately to escape the noise. However, despite the energy required, the researchers found that narwhal heart rates remained suppressed. In addition, rather than using underwater gliding to save energy, the narwhals swam more and dove faster than they typically would. This reaction caused the narwhals to use over twice as much energy.
Research shows that continued exposure to persistent underwater noise pollution can change a whale’s behaviour. The potential impacts include feeding less, altered intensity and frequency of calls, and stress. Chronic stress linked to noise pollution from shipping may cause multiple side effects, including growth suppression, lower fertility and poor immune system function.
© naturepl.com / Doug Allan / WWF
As our increasingly technology-driven world continues to rely on a linear rather than circular resource economy, the projected demand for minerals and metals is growing. Some opportunistic companies, with old-fashioned linear business models, are starting to look at deep seabed mining as a possible means to meet demand. However, experts in battery chemistry and technology, point out that deep seabed mining is not needed to meet demand. Instead, the focus should be on shifting to a circular economy and developing technological innovations. The regulatory environment is lagging behind this progressive thinking, and, as a result, the debate around deep seabed mining is kept afloat.
Deep seabed mining, should it be allowed to proceed, will cause a wide array of impacts on the ocean, including noise pollution, not to mention habitat destruction through the collection of mineral deposits from the seabed. Sources of noise pollution from deep seabed mining will include the noise generated by the mining machinery moving along the seafloor, the pipes and pumps transporting the material to the surface, and sea surface activities such as initial processing and disposal of sediment and other undesired materials in the water.
“There are two factors that make the potential impact of deep seabed mining different from other types of underwater noise pollution. Most of the anthropogenic noise in the ocean emanates from the surface – for example, ships, but with deep-sea mining, the sound will be coming from several sources throughout the water column, from the mining machinery at the seabed, through pumps mid-water, to the sea surface vessels,” says Christine. “And deep-sea mining obviously happens in deep water, where sound propagates well. Together, this means that noise footprints will likely be greater than in coastal waters.”
A lack of research
Current research assessing the potential impact of deep seabed mining has focused on the tens of thousands of species associated with the seabed rather than mobile marine wildlife such as cetaceans. Research has also touched on the potential impacts on fisheries, highlighting that tuna fisheries might be affected by noise, light, and the movement of ships at the sea surface, as well as the benthic and discharge plumes. To properly assess the potential impacts of deep seabed mining, it’s clear that more research needs to be done.
“At this point, to better understand the potential impact of deep seabed mining, we need to better understand the ecosystem in deep offshore waters. Noise characteristics, including received levels, will differ with depth in the water. This is because different types of noise are generated at different depths in subsea mining, and sound propagation differs with depth. We then need to investigate what noise characteristics have what effects on what animals,” says Christine.
© Alexis Rosenfeld
“Although we can use existing research detailing the impact of underwater noise on the behaviour of cetaceans to help determine the potential impact of the deep seabed mining, there are limits. There are many different engineering designs for subsea mining equipment, and we don’t yet have published noise source characteristics,” continues Christine. “Another concern is the cumulative noise from many different mines within the same larger geographic region, and what continuous, cumulative noise might do to cetaceans. For example, will these developments affect migration routes and behaviour?”
Protecting the seabed before it's too late
Ultimately, one thing is certain, the ocean is worth more than just the value of its finite resources. The intrinsic long-term benefits of a healthy ocean far outweigh any short-term incentives offered by deep seabed mining. Opening up this new frontier for extraction would destabilize delicate ocean ecosystems and fatally undermine the foundations of a circular ocean economy. There is widespread concern in the scientific community regarding deep seabed mining and the irreversible impact it would have on ocean ecosystems.
© naturepl.com / David Shale / WWF
Deep sea Cirrate Octopod (Stauroteuthis syrtensis)
© Erling Svensen / WWF
A cold-water coral, Lophelia pertusa, is a colonial bank-forming species of ahermatypic coral, found in deep, dark, cold waters.
WWF is calling for a global moratorium on all deep seabed mining activities. Extraction must not go ahead until the environmental, social and economic risks are understood, and all alternatives to deep sea minerals have been explored. Then appropriate regulation will be needed to protect the marine environment and human well-being.
Learn more about the growing resistance against deep seabed mining.