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When one thinks of all the dangers threatening whales and dolphins, ocean noise is not one that comes to mind right away, but is one that is increasing every day. A study showed that ambient noise in the oceans rose 10 decibels between 1950 and 1975 – a 900% increase in 25 years! The “Silent World” that Jacques Cousteau described years ago is no longer silent.
Marine mammals depend on sound to communicate, navigate and to search for food in our oceans. When we increase the ambient noise in the oceans, we decrease their ability to survive.
Sources of Ocean Noise A modern-day supertanker cruising at 17 knots (about 20 mph) fills the lower frequencies with a steady sonic roar of about 200 decibels, the equivalent of a commercial jet at takeoff.
The offshore oil industry relies on the explosive power of airguns, discharging tens of thousands of blasts as loud as 250 decibels.
The Navy is developing a “low-frequency” active sonar system, designed to detect foreign submarines by bombarding the seas with sound, reportedly in the range of 235 decibels or higher. (See Navy Noise!)
The federal government is preparing to test a new pulsed power “acoustic harassment” technology that will intentionally bombard marine mammals with potentially deafening underwater noise and disorienting shock waves for the purpose of determining whether California sea lions can be prevented from eating the fish caught by party boats. This noise will be as loud as 230 decibels!
Toxic Exposure
Toxic substances accumulate in the highest concentrations as they move up the food chain. Orca Whales, being the top predator in their environment, are more affected by pollutants than other sea creatures. Examinations of stranded killer whales have shown extremely high concentrations of lead, mercury and poly-chlorinated hydrocarbons (PCBs). These levels may be high enough to affect reproduction, immune function and endocrine function in the animals, resulting in their declining populations. These toxins are the result of abandoned marine toxic waste dumps and industrial and human refuse pollution into the oceans.
Dangers!
The following pictures may be difficult to look at, but if we are to protect cetaceans, we must be aware of the dangers that they face, from humans with which they share their habitat!
This whale caught her jaw on a cable below the sea and fought so hard to get free that she broke her jaw and died from infection, which also killed her unborn calf.
This whale was killed when its tail flukes were caught in fishing line. It became tangled then drifted for about a year before dying of starvation and dehydration.
Resource – Book
Killer Whales of Southern Alaska by Craig Matkin
Killer Whales of Southern Alaska
Resources – Book
Whales, Dolphins and Porpoises by Mark Carwardine
Whales, Dolphins and Porpoises
Resource – Book
Among Whales by Roger Payne
Among Whales by Roger Payne
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