The Ministry of Defence is being questioned over war games it conducted off the Scottish coast after several whales washed up dead suffering from the bends.
Scientists who tracked the war games, the largest in Europe, recorded an alarming number of sonar contacts over several days.
The noise was so loud that on occasions members of the Hebridean Whale and Dolphin Trust (HDWT) could hear the sound coming from headphones left in a neighbouring room.
The research comes as the MoD is being asked to explain the mysterious deaths of several deep diving whales washed ashore around Scotland and that have suffered from the bends.
Scientists who tracked the war games, the largest in Europe, recorded an alarming number of sonar contacts over several days. Pictured: A stranded beaked whale at Kearvaig Bag on June 10
The noise was so loud that on occasions members of the Hebridean Whale and Dolphin Trust (HDWT) could hear the sound coming from headphones left in a neighbouring room. Pictured: A stranded whale at South Uist in the Outer Hebrides
The MoD is being specifically asked if naval sonar used in the recent Nato war games, Joint Warrior, was responsible.
It is thought that the sonar waves can frighten deep-diving whales, forcing them to surface too quickly and leading to symptoms similar to decompression sickness, also known as the bends, in humans.
Investigators from the Scottish Marine Animal Strandings Scheme said the recent spate of beaked whale strandings was unusual.
And some had ‘an unusually high number and distribution of gas bubbles throughout the tissues’ – suggestion decompression sickness.
‘Given this was an obvious cluster of unusual cases, we were keen to gain what information we could from them,’ said a report by SMASS.
The first two cases were Sowerby’s beaked whales, which both live stranded on the Lothian coast.
The research comes as the MoD is being asked to explain the mysterious deaths of several deep diving whales washed ashore around Scotland and that have suffered from the bends. Pictured: A bottlenose whale at Faslane in Gare Loch
‘Neither animal had fed recently but both were in reasonable body condition, suggesting an acute cause of death. Notably, both animals showed an unusually high number and distribution of gas bubbles throughout the tissues- especially lung, liver and intestinal mesentery,’ said SMASS.
‘Whilst gas bubbles are not an uncommon finding during post mortem examinations, and can be a result of either decomposition or emphysema from the stranding process, a large number of bubbles, especially in deep diving species such as beaked whales, is suggestive of nitrogen emboli and decompression sickness (DCS).
‘Given how sensitive beaked whales are to underwater noise, specifically naval sonar, we have to consider noise-mediated DCS as a possible cause for these two strandings. We are therefore in the process of trying to find data on sources of noise in this region, including putting a request for activity logs to the MoD following the recent Joint Warrior naval exercises.’
The MoD is being specifically asked if naval sonar used in the recent Nato war games, Joint Warrior, was responsible. Pictured: Boats trying to heard bottlenose whales from Gare Loch
Three other cases involved northern bottlenose whale strandings – one at Stornoway in the Western Isles and two in the Clyde sea lochs.
Scientists aboard the HWDT research vessel Silurian – which was used in the BBC series Blue Planet – tracked the controversial massive Joint Warrior exercise, which ended on October 15, using hydrophones and other equipment.
Most of the training took place around Scotland’s north, north west and north east coasts and includes live-firing at ranges such as Cape Wrath in Sutherland.
‘We are concerned about how these exercises and training scenarios may be impacting the whales, dolphin and porpoise in our waters,’ said HDWT.
‘We are best placed to assess these impacts as we are the only organisation collecting long term monitoring data in the Hebrides. Military sonar used during these exercises can disturb cetaceans, who live in a world of sound, relying on their hearing to navigate, find food and communicate with one another.
Five whales have been found stranded off the coast of Scotland – Two at Clyde sea lochs, two at East Lothian and one at Stornoway
It is thought that the sonar waves can frighten deep-diving whales, forcing them to surface too quickly and leading to symptoms similar to decompression sickness, also known as the bends, in humans. Pictured: Life rescue boats try to heard bottlenose whales out of Long Loch
‘With conditions settling down we made our way across the Minch and recorded our first instances of military sonar.
What is the bends?
The bends, also known as decompression sickness, occurs when a bubble of nitrogen becomes trapped in a blood vessel and blocks it.
It usually affects divers who rise to the surface of the water too quickly and it can cause a fatal stroke or heart attack.
Surfacing quickly or holding in breath while coming to the surface can cause trapped air in the lungs to expand.
It may then rupture lung tissue which can lead to gas bubbles being released into arteries.
If the gas bubble blocks a small artery, it can cut off the blood supply to a particular area of the body.
The seriousness of the blockage depends on which part of the body is affected and the size of the gas bubble within the diver’s tissues.
A gas bubble can cause different problems depending on where the blockage is:
- Arteries leading to the brain – immediate loss of consciousness and may lead to fits or a stroke, causing confusion, dizziness and slurred speech
- Arteries leading to the heart – a heart attack or an abnormal heart rhythm
- A blood vessel to the lungs – a pulmonary embolism
These conditions are very serious and can be fatal, particularly if the condition isn’t treated quickly.
We heard sonar consistently throughout the next four days, some of which we could hear through the headphones without even putting them on – from the next room! We could even hear sonar when we were storm bound and tucked away in the Summer Isles.
‘In total, we covered over 550 nautical miles and collected over 85 hours of acoustic recordings.
‘We recorded military sonar on 14 per cent of the track lines conducted on the survey and dolphins whistles on 50 per cent. The hydrophone also picked up over 250 harbour porpoise, with over 1380 individual clicks. Five species of marine mammals were visually recorded including harbour porpoise, common dolphins, minke whales and grey and common seals.’
Naval sonar is still being investigated as a cause to why more than 90 deep diving whales mysteriously washed up along the Scottish, Irish and Icelandic coasts in 2018.
During previous surveys, which have coincided with the Joint Warrior exercises, HWDT has observed minke whales moving at high speed and leaping clear of the water, at the same time as military sonar was detected on hydrophones.
A pod of pilot whales stranded in July, 2011, at the Kyle of Durness, Sutherland, in what is believed to have been Scotland’s largest ever such event. Some 19 of the 70 whales died.
Four large bombs exploded underwater by the Royal Navy were later blamed by government scientists for the mass stranding.
A long-delayed report by the Department for Environment Food and Rural Affairs said that the noise from the explosions could have damaged the hearing and navigational abilities of the whales, causing them to beach and die.
But a spokeswoman for the MoD has said the Navy does all it can to ensure sonar is not damaging marine life.
‘The MoD takes its environmental responsibilities very seriously; environmental impacts are always considered in the planning of military exercises. During the planning of the exercise Environmental Impact Assessments have been produced and findings implemented where required, such as for the use of active sonar and live weapons,’ she said.
Exercise Joint Warrior saw eleven nations taking part, bringing 28 warships, two submarines, 81 aircraft and over 6,000 military personnel -including 130 ground troops – to military ranges across the country and to maritime exercise areas off the east, west and north coasts of Scotland.