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Ships' propellers creating underwater din

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  • Pacific Merchant Marine Council, NLUS
    Drowning in sound: Large ships propellers creating underwater din for whales, other marine animals
    Message 1 of 1 , Sep 5, 2009
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      Drowning in sound: Large ships' propellers creating underwater din for whales, other marine animals
       
       
      Posted: 09/04/2009 01:33:44 PM PDT
      Updated: 09/04/2009 01:33:47 PM PDT

      GULF OF THE FARALLONES NATIONAL MARINE SANCTUARY — As the 45-foot-white catamaran "Kitty Kat" bobbed in the ocean near the Farallon Islands last month, Jackie Dragon dropped a hydrophone overboard to capture the underwater sounds of an oil tanker gliding by a mile to the south.

      To those watching it from the catamaran, the 900-foot, black-and-white tanker cruised in majestic silence out to sea through the marine sanctuary, due west of the Golden Gate Bridge.

      But a speaker attached to the waterproof microphone soon broke the silence, as it transmitted the underwater racket caused by the tanker's propeller. To Dragon, the rhythmic churning resembles the sound of a freight train.

      "Now you really hear it," Dragon told a group of ecotourists and researchers on the Aug. 15 trip. The expedition was the first trip this year for the Vessel Watch project, which began in 2008 and is run by Pacific Environment in San Francisco.

      "It gets really obnoxious," said Dragon, head of the marine sanctuaries campaign for the group.

      Vessel Watch is the only effort thus far to monitor underwater noise from large ships passing through the nearby sanctuary, and it's among just a handful of such endeavors worldwide.

      The San Francisco group runs the program to gather data and cultivate public awareness about the toll of ship traffic noise on imperiled marine animals, many of which rely on sound for survival. With 100,000 large commercial vessels now crisscrossing the world's oceans, according to an estimate from the Chamber of Shipping of America, there's little escape from the noise generated by the ships' propellers.

      "We get to turn it off," added Ingrid Overgard, an ocean noise expert volunteering for the trip. "They have to live with this 24 hours a day, seven days a week."

      And the number of large oceangoing vessels is expected to double or even triple by 2030.

      "That is pretty much a given," said Kathy Metcalf, a former deck officer on oil tankers and director of maritime affairs for the Chamber of Shipping of America.

      Scientists only have scratched the surface of knowledge on the effects of human-caused noise on marine animals, in part due to the difficulty inherent in ocean research. One oft-cited 2006 study, however, reported that underwater ship noise doubled every decade off the Southern California coast since the U.S. Navy took measurements in the 1960s, rising 10 to 12 decibels during that time.

      In an unlucky coincidence, the low-frequency sound generated by ships falls in the same range used by whales to communicate, and it's capable of traveling hundreds of miles through water without diminishing.

      Hearing a problem

      Many marine animals rely on their hearing to live in the murky or pitch-black waters that make up much of the ocean. In that dark realm, hearing reigns as the chief sense.

      But when human-caused noise is added to the mix, the animals' own attempts at communication may be masked. It can also interfere with their efforts to locate prey, detect predators and can cause them the abandon prime feeding or breeding habitat.

      In a 2005 report from the Natural Resources Defense Council, called "Sounding the Depths II," the organization described ship noise pollution as "death from a thousands cuts," especially for already-threatened species.

      The report also describes harm caused by underwater sonar used for military purposes or for oil exploration, which experts from the International Whaling Commission and the U.S. Navy agree is linked to mass strandings of whales.

      But a number of scientists think the cumulative effects of chronic noise pollution from merchant vessels could pose an even greater threat to marine mammals than the intermittent blasts from sonar.

      It's a newly emerging issue, and an initial challenge is raising awareness about it within the international shipping industry, according to Metcalf, with the shipping association.

      She only learned of it after receiving an invitation to a 2004 conference run by the National Oceanic and Atmospheric Administration, called "Shipping Noise and Marine Mammals." It was the first scientific symposium on the topic.

      Since then, she has become something of a change agent, pushing for naval designers to incorporate "noise quieting" technologies into new ships, primarily with new propeller and hull designs.

      "A lot of people, when a new issue comes up, say, 'I don't see proof that it's a problem yet, so let's just pretend like it doesn't exist,'"‰" Metcalf said. "We took a different tack on that. We said, 'You know what, if it's an issue, let's get in on the ground floor and talk about it.'"‰"

      Curing sounds' fury

      Most undersea sound generated by ships comes from their propellers. As the blades turn, they create thousands of tiny bubbles, a process called "cavitation." The sound of these bubbles bursting is the main source of ship noise pollution. Ship engines are a distant secondary contributor, she said.

      And cavitation means wasted energy. "Cavitation and propellers equal inefficiency," Metcalf said.

      Environmental groups also support improved ship design as a critical step toward reducing shipping noise. But a 2008 report from the International Fund for Animal Welfare, called "Ocean Noise: Turn it Down," also advocates for the more immediate remedy of rerouting commercial vessels around sensitive habitat when whales and other imperiled animals are present, and slowing down ships when entering those areas.

      "The magic number is 10 knots," said Dragon, with Pacific Environment. "If ships were traveling slower, they'd be cleaner, they'd be quieter and they would be safer," she said, alluding to ship strikes, which in 2007 killed four blue whales in shipping lanes off Santa Barbara.

      But Dragon also acknowledged the issue is a "nonstarter" with the shipping industry, at least as a voluntary measure.

      Metcalf concurred. Slowing down ships from cruising speeds of 25 knots would lead to more ships on the ocean, because it would delay arrival times for in-demand products, she said. And a sanctuary speed limit would add many hours to voyages, piling on costs. The restrictions would be onerous for large vessels traveling along coastlines, Metcalf added, which are replete with sensitive marine habitat.

      Remedies in water

      Retrofitting existing ships with propellers that create less cavitation is also proposed as near-term remedy. Metcalf said that's possible for some ships, but existing hull shapes make it "virtually impossible" for many others.

      A 10-knot limit when whales are present took effect this year for liquefied natural gas carriers at Stellwagen Bank National Marine Sanctuary in Massachusetts, and its adjacent waters. Another restriction took effect in 2008 on the Eastern Seaboard, requiring the slowdown of all large ships during the season that federally endangered right whales congregate.

      Metcalf said the economic effect of the seasonal slowdown on the shipping industry "was huge."

      The federal regulations were enacted to protect the whales from death and injury by ship strikes, which have increased in recent decades on the East Coast. But they have the ancillary effect of reducing ship noise, said Leila Hatch, an ecologist who runs the underwater acoustics program at the Stellwagen marine sanctuary.

      Scientists at Stellwagen are overseeing a new underwater acoustic array that's adding data to scarce research on the issue. "We're probably the farthest along in the world looking at shipping noise and whale behavior," Hatch said.

      A small, vital program

      Seeing a similar system of acoustic arrays established at the marine sanctuary surrounding the Farallon Islands is a "dream" for Carol Keiper, the naturalist on board the catamaran.

      Between excitedly pointing out porpoises, seabirds, and gray, humpback and blue whales for passengers, Keiper said, "They have all this amazing technology set up at Stellwagen."

      For now, the small Vessel Watch program is the only research on the topic for the Gulf of Farallones sanctuary, which is particularly rich in marine life. It relies on the tourists joining the trip donning the hat of "citizen scientist."

      During the seven-hour journey, they can help monitor the presence of whales in a shipping lane and take photos of any breaching animals. The data is shared with scientists studying whales off the coast of California, and recordings of underwater ship noise are sent to a researcher at Scripps Institution of Oceanography.

      "We very much want to elevate the role of science," said Dragon, with Pacific Environment. "The No. 1 argument for not changing anything is the lack of sound science that proves a change is needed."

      For details on the Vessel Watch program, which runs through November, go to http://www.pacificenvironment.org/.

      ______________________________

      http://pacificenvironment.org/blog

      First Trip for Vessel Watch

      August 21st, 2009

      Whale Fluke by Laura Wais

      Picture by Laura Wais.

      By Jackie Dragon

      The others were out on deck craning their necks at the red underbelly of the Golden Gate Bridge, gazing at seals and sea lions draped over the rocks around Point Bonita, and dreaming of a day full of whales at Farallon Islands. I spent the first full hour of my prep trip for our upcoming Vessel Watch Project wrestling with my computer. Actually, I was doing the very thing one should not do, unless you are trying to get seasick – staring closely and long at a stationary object while our boat rocked and then picked up speed, riding softly bucking waves out to the islands. No worries though; I kept my stomach in place.

      The whole point of this trip was to get all the technology glitches worked out before our first trip on August 15. I was trying to get our Automatic Information System (AIS) antenna and receiver to pour real-time data from any near-by ships onto our computer screen. Then, when we encounter any of the thousands of giant ships that drive through the Gulf of the Farallones National Marine Sanctuary to our busy ports we can get the skinny on it, so to speak. The AIS can tell us the ship’s name, destination, ship type, as in cargo or oil tanker, and how fast that ship is traveling through these rich and biodiverse waters. The faster a large ship goes, the noisier it is in the water. Most of the noise is caused by cavitation, created when thousands of tiny bubbles form and burst as the propeller turns. Captain Joe, quite a technology buff himself, turned the wheel over to his deck hand, Steve, and joined me to try his hand at the stubborn computer. Finally, we surrendered to defeat…but just for today. We’ll get this system humming.

      Never fear, I had more mechanical toys to test, and unpacked the hydrophone, digital recorder and mini amplifier. I asked Captain Joe if he thought there would be a good time to stop the boat today, as I wanted to lower the hydrophone and see what we could hear. He replied affirmatively in his usual bright tone. Joe is a fisherman transformed by the changes in our oceans, and our depleted fisheries. Now he turns his boat and expertise towards ecotourism and research. Captain Joe and S.F. Bay Whale Watching go beyond ferrying ocean enthusiasts out to find whales. They partner with anyone who needs to get out on a boat to make a positive difference in these waters. Joe conducts water quality sampling for the state, releases rehabilitated seals and sea lions for The Marine Mammal Center, and even turns off the boat so our Marine Sanctuaries Campaign can bring the underwater world of sound up on deck. Our goal is to open ears to the threats of ocean noise pollution facing whales and marine life in the sanctuary.

      A wave of questions, “Are we getting close?” and “How much further to the islands?” washed over the boat. A few minutes later Capt. Joe’s voice came overhead reminding passengers that a free t-shirt was the prize for spotting the first whale. We were about five miles out from the islands and in prime whale territory. Seconds later Steve, called out “There she blows!” I caught the faint remnant of a short heart-shaped misty blow. A minute later, directly in front of our boat’s bow, we watched the knuckled back of a grey whale roll into a graceful dive, finished with flukes slipping below the surface.

      And then, we saw a lot of nothing. That first-whale excitement gave way to concern as 46 pair of eyes scanned the water in vain. Capt. Joe wondered what kind of activity was happening on a large retrofitted crabbing vessel trolling nearby. Might they be driving the whales away? An older gentleman on his ninth trip out to the islands, the last time six years ago, told me he had never seen it “so dead.” Finally, we turned and drove in for a closer look at the wild Farallon Islands. Trish Mirabelle, our naturalist for the day, captured our attention with stories of egg wars on the islands in centuries past, and the research on birds and white sharks and pinnipeds that has followed for the past 40-some years.

      And then, more whales. Humpbacks this time. Three swimming together, flukes over one at a time. We hung around them at a safe distance ooohhing and aahhhing just to see them. Another humpback breached off in the distance. The whales were here, after all! Just as I was getting antsy wondering if we might get the chance to hear these magnificent creatures, as well as see them, I heard the sound I was waiting for – quiet! Joe had cut motor.

      I was already lowering the hydrophone over the side when Trish came to tell me we were stopped for a listen. I turned on the little amplifier and hit the red record button. The relative quiet on board was replaced by sound pouring out of the little box. Passengers gathered around. We could hear the water slap, slap, slapping against the metal hull, and lots of crackling in the background – the tell tail sounds of snapping shrimp. And then, we heard them. Whoop, whoop, whoop… Nobody spoke. We just turned wide-eyed at each other and mouthed the word WOW! For thirteen minutes we floated while whales swam, dove, and fed all around us. Intermittently we heard squeaks, moans and gulping sounds. Three whales turned into seven or eight and they seemed content to swim around our floating boat, sometimes quite close. I couldn’t help wondering if turning off our own noisy motor gave the whales a chance for a closer look at us. Our nine-trip veteran said he had never seen so many whales ever before.

      _______________________________________

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