How Is Shipping Affecting Seals?

New research conducted by scientists at the University of St Andrews suggests that seals living within the vicinity of busy British shipping lanes could be at risk of hearing impairment as a result of noise pollution.

Comparing sea mammals which live inside shipping channels to humans residing in bustling urban metropolises, the study said that communication and hunting methods of animals such as seals, dolphins and whales could be jeopardised by extensive underwater vessel noise pollution.

At high risk

The study, published in the Journal of Applied Ecology, found that an alarming 11 out of 25 Special Areas of Conservation (SACs) around the UK were at high risk of exposure to vessel traffic. Water pollution has been linked to the nautical industry in the past, with sophisticated photometric testing methods being used to determine concentrations of iron in drinking water supplies.

In addition to contaminated water, a high volume of vessel traffic also comes with another risk – noise pollution. The St Andrews team analysed decibel levels in the Moray Firth using predictive acoustic modelling software, thus determining how many seals and other mammals were exposed to the pollution and at what level.

Temporary deafness

In addition to a raft of other effects of noise pollution on marine life, the team found that 20 out of 28 specimens tested were subjected to decibel levels high enough to cause temporary hearing damage.

“The UK has some of the busiest shipping lanes in the world, and underwater noise has been increasing over the last 30 years,” explained Dr Esther Jones, a research fellow at St Andrews and lead author on the study.

“This is particularly pertinent to harbour seals that are declining in some regions around the UK, as half of SACs associated with them had a high risk of exposure to shipping. Exposure risk was highest within 50km [31 miles] of the coast and any impacts will have the greatest effect on harbour seals as they generally stay close to land.”

An ongoing problem

Fortunately, there was no evidence that the seals had been exposed to noise pollution serious enough to cause lasting damage to their aural faculties. However, Dr Jones warned that such a fact should not be a cause for complacency, since the situation was almost certain to deteriorate.

“Urbanisation of the marine environment is inevitably going to continue, so chronic ocean noise should be incorporated explicitly into marine spatial planning and management plans for existing marine protected areas,” she added.

Rerouting shipping channels would obviously entail substantial planning and no little financial investment, but what price can be put on marine conservation? If it helps to save the eardrums – and ultimately, the longevity – of native UK species such as the seals in question, it could well be worth the outlay.