Marine wildlife is being killed, deformed, injured, traumatised and subjected to dangerous levels of stress by a crescendo of underwater noise from ships and offshore industry, scientists are warning.
Whales, squid, fish, crabs and shellfish are all suffering from the rising din being made by propellers, engines and subsea drilling, prompting demands for quieter ships and the introduction of "quiet areas" in the seas.
Hundreds of marine biologists from across the world gathered in Glasgow this weekend for the International Marine Conservation Congress, organised by the Society for Conservation Biology. They heard mounting evidence of the widespread damage to animals being caused by underwater noise.
Over the last half-century, low-frequency noise in the oceans has increased by at least 20 decibels. Most of the noise comes from ships, which are carrying three times the weight of cargo they did in 1970, amounting to more than 80% of all the world's freight transport.
A series of expert studies from three continents has shown a large variety of ways in which noise can harm wildlife. Squid and octopus were found to suffer massive acoustic trauma destroying cells vital for balance and orientation.
Scallop larvae were delayed in development and deformed by noise, the internal organs and ovaries of snow crabs were bruised, and eels showed signs of stress. In another study, noise killed the eggs and young of sea hares.
The studies were showing worrying trends, according to Sarika Cullis-Suzuki, one of the conference organisers researching fish and noise in the north-west Pacific. "The oceans already face a multitude of threats," she said. "By adding yet another stressor like human-generated noise, the consequences could be severe."
The evidence that noise disturbs many types of marine life was accumulating, Cullis-Suzuki added. It was also a problem that could be addressed "relatively easily" by building quieter engines, she argued.
Matt Wale, a researcher at the University of Bristol and then Edinburgh Napier University, has discovered that playing ship noise to shore crabs affects the way they behave. It can distract them from food, delay them hiding from predators and make them breath faster, resulting in "elevated risks of starvation and predation".
A study in Nova Scotia's Bay of Fundy by the New England Aquarium in Boston, US, concluded that North Atlantic right whales suffered chronic stress from ship noise.
Dr Rob Williams, a Canadian marine scientist who recently completed research at the University of St Andrews, discovered that in busy shipping lanes whales could be deprived of 90% of their opportunities to communicate with members of their family. Killer whales also reduced the time they spend feeding by up to 25% when boats were around.
"We know that noise affects communication, hunting success and behaviour of individual animals," he said. "That could affect the whales' ability to have or nurse calves."
He urged the adoption of quiet marine protected areas and economic incentives to build quieter ships using technologies developed by navies. "Preliminary calculations suggest that the noisiest 10% of ships produce 80-90% of the noise," he said. "We don't need to ask everyone to quiet their ships, just the noisiest."
Lang Banks, director of WWF Scotland, pointed out that noise pollution could cause long-term damage to marine species. "To address the potential threat we need to see quieter ships as well as action to reduce noise levels from shipping in especially critical habitats," he said.
The UK Chamber of Shipping welcomed accredited scientific research that helped understand the problem. Chief executive Guy Platten said: "Industry, government and environmental groups recognise that as old ships are decommissioned, and new ships come into service, significant progress will be made in reducing the noise impacts from shipping."
UK Oil & Gas, which represents the offshore industry, described the research as inconclusive and did not sound keen on quiet zones. "The first priority is to better understand the various sources and cumulative levels of sound energy the industry produces in the marine environment," said a spokeswoman.