4 minute read
Ocean symphony
Illustration Sally Elford
Human underwater acoustics are causing chaos for ocean creatures, but how do we keep the peace? FRANK dives beneath the waves to find out more about the sound of silence.
When Jacques Cousteau made the pioneering underwater documentary The Silent World in 1956 he brought the colors and sights of the ocean into living rooms around the world. But despite its ground-breaking progress, scientists now consider the title to be misleading. The planet’s oceans are in fact accompanied by a rich soundtrack. These noises are essential for sustaining marine life and need to be protected.
Professor Steve Simpson has been listening to the sea since he was a young graduate student and is an agent for positive change. “What’s exciting about working on ocean noise pollution is that we’ve identified the problem, we know where it’s coming from and most people producing the noise have an affinity with the ocean and want to do what they can to improve the situation,” he says.
Encouragingly, the sectors contributing the loudest noise often have the best resources, notes Professor Simpson. “With offshore renewable energy, commercial shipping or the oil and gas industry there are generally lots of engineers who love problem solving and looking for solutions.”
The impact of human noise pollution is generally measured by population sizes for fish or signs of stress in whales and dolphins. An altered soundscape can make animals and fish less aware of their predators and can also have a detrimental impact on breeding, as well as the ability to find suitable habitat.
“Whales can communicate over hundreds of miles as they interact with each other,” says Professor Simpson. “Fish speak by making popping, grunting, whooping and trumpeting
sounds to warn each other about predators or calling each other over when they find food. There are breeding songs - love songs, even. Sound is essential to their lives.”
With each decade of economic growth, scientists have found a 3.3dB rise in ambient noise levels largely attributed to commercial shipping. What’s encouraging is that the volume can be turned down. In an academic article published in Science entitled ‘The Soundscape of the Anthropocene Ocean’, scientists led by Professor Carlos Duarte discovered that amid the global pandemic a slowdown in trade caused the volume to reduce by around 20%. During lockdowns, the recovery of habitat was dramatic. The report notes that with approximately 58% of the global human population indoors, marine mammals and sharks were observed in previously busy, noisy waterways. “This unusual behavior has been linked to reduced anthropogenic noise during human confinement,” the report states.
In Canada, progress has been made simply by slowing commercial shipping speed limits and creating reduction zones for whales to breed uninterrupted. In recreational yachting, the building of new marinas, as well as noise from engines and water toys, are the main contributors. That said, Professor Simpson has discovered that some marine animals can become habituated and “tune out” noises, such as generators in marinas.
“There are several strategies for tackling marine noise pollution,” he advises. “The first is technological innovation, the second is spatial management and the creation of a buffer zone around sensitive habitat, and the third is temporal. So, if you know there’s a season when noise is going to have an effect, you move the noise elsewhere.”
Simpson has been working with the Great Barrier Reef Marine Park Authority to create quiet sail and paddle only zones. “We also have a PhD student measuring the acoustics
of sailing regattas, perhaps not from the sailing yachts themselves but from the support and spectator vessels. We’re looking at ways to engage with people who care about the ocean and use high-profile events for promoting best practice.”
Marine species will also benefit from yacht owners demanding increasingly silent yachts, with some shipyards investing in a dedicated acoustic department. Oscar Propulsion is a UK-based environmental technology company engaged in the development of a noise-reducing propeller whereby holes called PressurePores are drilled into the blades to reduce tip vortex cavitation (the noise made by collapsing air bubbles).
The engineering and testing have been carried out together with several of the UK’s leading universities. Full-scale sea trials have shown a 10dB reduction in noise levels, validating the results from model tests in cavitation tunnels. The impact on efficiency is considered very small, and the option to retrofit propellers on commercial vessels and superyachts is promising.
“We are working with the leading propeller manufacturers, and existing propellers could be made less noisy by drilling them with a carefully calculated pattern of holes,” says Oscar Propulsion director Lars Eikeland. “Ultimately, it’s the ship owners we have to convince.”
In contrast to our global carbon footprint, ocean noise pollution can be dramatically improved in a relatively shortterm future. For a well-managed healthier ocean, Duarte’s report suggests less ship traffic, quieter propellers, floating turbines, quiet AUV and a seafloor-based seismic survey.
“It’s an obvious issue with a fairly obvious solution,” concludes Professor Simpson. “With the desire to change we will see an improvement quickly. I remain optimistic about the ocean. It’s a phenomenal self-healing ecosystem.”
To paraphrase acid jazz group Freak Power, it’s down to us to tune in, not cop out.
