Improving noise protection for sea mammals

World Oceans Day

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New updated technical guidance on how certain noise-generating activities at sea may affect marine mammals has been released by the US National Marine Fisheries Service.

The issue of underwater noise has already made it into the courtrooms and even legislative bodies in recent years. According to certain studies, naval sonar devices can send whales into a panic that may, in some cases, even be fatal to them. Cargo ships that cross the oceans in large numbers every day are also thought to cause dangerous noise for sea creatures.

Another major activity that generates noise is the seismic surveying carried out by oil companies. To assess layers of rock on the seafloor, so-called air guns are used to shoot high-pressure bubbles into the sea. The sound this creates is then used to study seabed geology. The oil industry maintains that these methods are harmless. Environmentalists, however, have a different opinion. Many sea creatures use sound not only for direction, but also for finding food and for communication.

The dispute between environmentalists and the oil industry has been brewing for a long time, but things appear to be changing. The US National Marine Fisheries Service (NMFS) published a position paper at the end of last year that is likely to change granting of authorizations for noise-generating activities in the oceans. The paper means that it will now be necessary to study in more detail to what extent air gun bubbles harm marine mammals.

There are currently few studies that show how animals are affected by seismic surveying. Only very rough noise exposure guidelines were released by the US authorities in the 1990s. For instance, it was assumed that whales suffer temporary hearing loss when they are exposed to nearby sound exceeding 160 dB. Seals, however, are thought to go deaf when exposed to 190 dB. The new guidelines now refer to other factors such as frequency and modulation of sound to take better account of the specific hearing abilities of each species. The guidelines now divide marine mammals into five groups, since they react differently to noise. Further studies are expected.

Environmentalists have welcomed the position paper. The oil industry, however, prefers to wait and seen and has warned that paperwork is likely to become more complex.

World Oceans Day was celebrated on sunday 8th June 2014. Learn more on worldoceansday.org

Source: www.sciencemag.org

C.S.