Wednesday, February 8, 2012

Underwater Noise Abatement: good news/bad news for marine life

Possible good news/bad news for ocean noise pollution. First the bad news. A research study from the New England Aquarium in Boston provides the first documentation of harmful stress on whales due to elevated noise levels from ships.

A "Before & After" Research Opportunity
The issue of ocean noise pollution has been around for some time and hotly debated depending on whose side you're on. Construction noise from oil drilling platforms or other such ocean-based structures, sonar signals from naval vessels, even underwater explosions as part of oil and gas exploration - all have been subject to intense scrutiny and more from various environmental groups (there are lawsuits currently against the U.S. government regarding submarine sonar sounds).

But sometimes having the definitive proof can be challenging. To measure the effects of noise pollution you need, as a basis of comparison, a period of little or no sound and an examination of the health of animals within that environment. Then compare it to a noisy environment. Those set of circumstances don't come along every day. Until September 11th, 2001.

Northern right whales are a highly endangered whale, due to years of whaling pressure followed by intense shipping along the whale's coastal migratory routes up and down the east coast of the U.S. With the advent of September 11th, for national security concerns, shipping was sharply reduced following the attacks. This provided a window of opportunity for New England Aquarium researcher Rosalind Rolland to study the condition of the whales during a "quiet" period. And how do you do that? Why, by studying whale poop, of course.

Researchers can measure stress levels in whales by examining stress hormone levels found in the whales' waste - fecal balls that float to the surface. Rolland's team measured significant reductions in stress hormones during the lull in shipping following the terrorist attacks. Stress levels were again high when shipping activity returned to pre-9/11capacities.

"We showed whales occupying oceans with high levels of ship noise have a chronic stress response. We knew whales changed the frequency of their calls to adapt to the ship noise, but this work shows it is not merely an annoyance – it is having a physical effect," said Rolland. "Instant responses to stress – like running away from a tiger – can be life-saving. But if it becomes chronic, it causes profound depression of the immune system, making them vulnerable to disease, and it depresses reproduction."

With the cause and effect evidence at hand, the question is what do we do about it? Shipping is far too vital of an economic enterprise for many nations to simply decide to curtail it on behalf of the whales, regardless of how that would please marine mammal advocates.

"The positive aspect to this particular issue is that it is a solvable problem," Rolland said. She believes that much of the problem can be addressed by making the engines more efficient. As an example, a lot of design has gone into making submarine screws (propellers) more efficient and quieter, thereby providing a tactical edge militarily. If that same engineering effort could be put towards conventional ships, a marked reduction in overall noise levels could be achieved - along with fuel saving benefits in the process. It's possible; however, it will take some time. The Guardian reports that there are approximately 50,000 ships at sea on any given day. That's a lot of vessels in need of costly retrofitting.

"Amazingly, there are currently no accepted international standards regarding noise pollution in our seas," said Danny Groves of the Whale and Dolphin Conservation Society. "Not enough is being done to reduce noise in our oceans Very little is known about its long-term effects and more research is needed." Hopefully, the New England Aquarium's research data will help the cause.

Possible Good News for Noise Abatement
The construction and operation of oil platforms or other offshore structures, like wind turbines, can produce noise levels that are harmful, if not outright deadly, to marine life. The process of driving in pilings with the construction of energy platforms can produce sound waves of such intensity that they can kill fish. The initial pressure wave from, say, a pile driver compresses the air in a fish's bladder. With the passing of the pressure wave, the air suddenly expands, rupturing the bladder and causing other organ damage. However, ongoing research is using that same compression of air to provide a possible solution: bubble curtains.

A little over eight years ago, the California Department of Transportation (Caltrans) utilized a wall of bubbles to dampen the impact on surrounding marine life from piles being driven for a retrofitting of the San Francisco-Oakland Bay Bridge.

According to marine biologist Bud Abbott, who was working as a consultant on the Caltrans project, the bubble curtains work by altering the pressure wave's intensity, "When a pressure wave hits an air bubble, it will compress the bubble, then it will expand again, so energy is lost. Sound travels faster through water than air. It slows down as it hits the air bubble."

Although some scientists debate the extant to which energy is lost, Abbott says the curtains alter the pressure wave, changing it from a sharp, destructive force to a smoother, less destructive wave pattern.

According to National Geographic Daily News, an offshore turbine farm being built in the Baltic Sea by a consortium of German energy companies will incorporate bubble curtains to reduce construction and operation noise to government-mandated levels of no greater than 160 decibels at approximately a half mile. Additionally, Shell Oil is looking into the use of bubble curtains to provide some measure of protection for Arctic marine life, including some endangered marine mammal species, as part of their licensed permits to build and operate energy facilities in the Arctic.

Mitch Winkler, manager of the Arctic Technology Program for Shell International Exploration and Production, said,
"We are focusing on the use of air bubbles and their impact on sound waves as a means of reducing the sound transmitted from stationary sources. We are targeting a reduction in the amount of noise by as much as ten decibels."

While the U.S. Marine Mammal Protection Act has specific noise level limitations designed to protect marine mammals, many environmental groups, while applauding the efforts toward noise abatement, feel there are even graver threats to Arctic ecosystems from oil and gas companies.

"We're certainly in favor of using and testing any new methods of reducing sound from human activities underwater," said Brendan Cummings, senior counsel for the Center for Biological Diversity. "[The concept of] "bubble curtains is raised pretty frequently, although there are few real-world applications of it. But there are far bigger problems than the noise impacts, including the simple fact that there is no technology, methodology, and—most important—no infrastructure in place to deal with an oil spill in the Arctic."

True. Drilling in the Arctic is fraught with ecological hazards and it is an ongoing political tug-of-war between environmental concerns and current pressing energy needs, even while alternative energy systems continue to develop and expand. However, for the construction and operation of any offshore facility in the world - oil, wind, or otherwise - at least there is one form of technology that appears hopeful in providing marine mammals with some measure of protection.

Source: The Guardian
National Geographic Daily News

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