February 25, 2008 The unlucky passenger who died when a high-speed ferry rammed into a sperm whale in the Canary islands was the world’s first known victim of a new form of pollution – ocean noise.
Worldwide, the number of ships and pleasure craft that come into collision with large sea creatures is climbing inexorably – and the insurance bill with it – as numbers of both vessels and whales multiply and the sea-lanes become more crowded.
The cause of the accident, says marine biologist and Rolex Awards for Enterprise Laureate Michel André, most probably lay in damage to the whale’s sensitive hearing apparatus caused by the rising roar of man-made noise throughout the oceans. The whale was stone deaf – and simply didn’t hear the ferry coming in time to avoid it.
What no-one expected when conservationists forced an end to commercial whaling was that whale numbers would one day rebuild sufficiently to become a hazard to sea craft. But in places where marine traffic is heavy, vessels fast and whale numbers expanding, violent encounters are increasingly common. Where the ship is large the whale comes off second best, but in the case of cruisers, yachts and smaller vessels, damage can be mutually serious - even deadly.
We often speak of the “silent deep”, but the exact opposite is true. Sink a few metres into the ocean, and light begins to fade. At 40 metres you enter endless night, where eyes are of little use and hearing is all. Here, noise moves five times faster - and much farther - than on land. High frequency sounds decay rapidly but low frequency noise can travel right around the planet using a special “sound channel” in the oceans, centred about a kilometre down. The oceans are the true realm of sound.
Most sea creatures – from whales and dolphins to fish, squid and shrimps – respond to sound, and many produce it. They use it to hunt and to avoid the hunters, to find mates and food, to guide schools of fish, to navigate, to send messages and transmit warnings, to establish territories and warn off competitors, to stun prey and deceive predators, to “illuminate” their surroundings acoustically, to avoid obstacles and sense changes in water and conditions. They click bones and grind teeth. They use drum-tight bladders and special sonic organs to chirp, grunt, sing and boom. They belch gases and liquids. They vibrate special organs or their entire bodies. They gather to form great choirs. Sounds emitted by sea creatures span the range from 0.1 hertz to 300 kilohertz.
Far from the “silent deep”, the oceans are a raucous uproar.
Into this age-long tumult, in the blink of an evolutionary eye, has entered a new thunder: the throb of mighty engines and the thrash of propellers as 60,000 huge vessels plough the world’s sea lanes; the hammer of diesels and scream of outboards as 4 million fishing boats and more than 10 million ferries and pleasure craft surge to and fro; the thump and ping of military and fishing sonars; the deafening crash of seismic ships seeking oil and gas; the blare of acoustic harassment devices; the grinding of drills and dredges; the low-frequency growl of scientific experiments designed to monitor global warming.
Scientists report that background noise in the ocean has increased 15 decibels in the last half-century and 1000-fold since the industrial age began. This is enough, scientists say, to mask and scramble the normal sounds of ocean life going about its business.
Dr Michel André, for one, is convinced the human uproar is killing whales – and now, apparently, people too. “One of the major short-term and worldwide threats for the sea and marine mammals is constituted by the noise produced by artificial sources,” he says.
In the Canary Islands between six and ten whale collisions a year were being reported, mainly by fast ferry services. When a passenger died after a high-speed ferry rammed a basking sperm whale, André, a marine acoustics expert at the University of Catalonia, was asked to investigate. He decided to start by studying the dead whales. The first two he examined showed severe damage to their inner ears. They were, in short, deaf to certain sounds.
“The inner ear lesions we found in sperm whales came from two resident whales which died after collisions. These lesions affected animals of different ages,” he says, indicating the damage is due to an external factor, not to ageing.
The injuries also occurred at a place in the ear’s sensitive structure corresponding in frequency with the sounds emitted by shipping. To test whether the wider whale population was affected, his team ran controlled exposure experiments on 215 sperm whales in the Canaries in which they played sounds in the same low-frequency range as the affected regions of the ears. The whales failed to react.
While it is impossible to be scientifically certain, Michel André felt that the correspondence between the sound frequency emitted by shipping, the area of damage to the whales’ ears, and the lack of response by other whales to sound broadcast at the same frequency built a compelling argument: “It is very likely that these lesions are due to a long-term exposure to low-frequency sources.”
Since that time, evidence has accumulated around the world that whales are being deafened by human activity. Anatomical evidence indicates that high-intensity sounds such as those produced by active naval sonar cause lesions in whales acoustic organs. These may ultimately kill the whales by causing them to strand, collide with vessels or fail to locate their food sources and so starve.
Aiming to overcome the collision problem André and his team have developed the world’s first whale anti-collision systems (WACS). Knowing that active sonar will only further confuse the whales, he and the team have designed a passive system consisting of a chain of ultra-sensitive listening devices that detect whales round-the-clock, and transmit warnings to nearby vessels. The devices detect the sonic clicks emitted by the whales as they seek prey or communicate with one another. For silent whales, they use sound from other ocean sources, such as waves or rain, reflected off the whales themselves.
A remarkable feature of his system is its ability to single out and track an individual whale among all its “family” members in the same area – a breakthrough made with the help of a West African musician. After years of research, André’s discovery that the sequence of acoustic signals transmitted by the sperm whales could be used to identify individual mammals – a process called Rhythmic Identity Measurement (RIME) – was almost by chance. In attempting to unravel the chaotic rhythms of the sperm whale clicks, he was struck by the similarity between his underwater recordings and African tribal music. A Senegalese griot (drummer) confirmed the likeness and – amazingly – was able to pick individual whales from André’s recordings through their distinctive rhythmic structures.
In 2002 André received a Rolex Award for Enterprise for his project, which kept it alive through numerous technical challenges. The technology underwent successful sea-trials in the Mediterranean a year ago, where it detected artificial “clicks” up to two kilometres away with ease, he says. “We can now guarantee the underwater antenna works well,” he says. The low frequency sounds made by sperm whales, for example, can probably be detected as far as 10-15 kilometres away.
The next stage is to test the technology using real whales, and to do this André is now raising funds for trials off the Mediterranean’s Balearic Islands through his foundation Sons de Mar.
If these are successful his plan is to commercialise the technology for worldwide application wherever there is a problem with whales and surface vessels – in the busy sea-lanes off Japan, or off Boston harbour in the US for example, where there is a critically endangered population of right whales. And, he adds, off the coasts of Australia and New Zealand where yachts and pleasure craft report increasing numbers of whale encounters.
André says his WACS has other applications besides helping to prevent collisions between whales and ships, including its use to improve human safety in ocean yacht races. As a scientific instrument it can be used to study the daily lives and behaviour of whales in hitherto undreamed-of detail. For whale watchers and tour operators, it may provide a new way to observe and marvel at these giants of the deep.
One of its most important roles is to make humanity more aware of the problems it is causing in the oceans through noise pollution – just as it has become conscious of the impact of chemical pollution on rivers and carbon dioxide emissions on the climate. Silencers, developed for Naval use as stealth technology, can now be fitted to ships and pleasure cruisers which cut their noise penetration to a few metres by shrouding the hull in a curtain of fine bubbles. It is time for environmentally-conscious boat owners to consider such things, he says.
“The more noise we put into the ocean, the more we affect the way sea life communicates and lives,” the Rolex Laureate says. “This means that we are compromising their survival … the way they find their food and the way they breed. Nowadays there is no region around the world that is not affected by noise pollution. Due to its low-frequency components, a sound source may propagate over thousands of miles. The control of these sources constitutes a scientific challenge and an important responsibility for society, governments and all those who use the oceans.”
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