Resounding deaths

Whales and dolphins could be dying because of noise pollution. Researchers from the Navy Marine Mammal Programme in San Diego, USA, claim that noise from the US navy sonar and explosives tests as well from tankers and oil exploration activities is causing mammals to dive deeper, thereby, increasing their chances of getting 'bends', which can kill. When an animal dives, nitrogen gas is squeezed out of their lungs. Thereafter, it bubbles into their bloodstream. Too much nitrogen in their blood can kill them, so when they surface, whales and dolphins breathe out to get rid of the dangerous bubbles. But experts think that noise from sonar and blasts can make the gas bubbles in the bloodstream so big that they block blood vessels and crush nerves (news.bbc.co.uk, December 17, 2001).