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CORDELL BANK NATIONAL MARINE SANCTUARY — Motoring across the steel-gray surface of the Pacific Ocean on a scientific vessel loaded with high-tech equipment — the vast horizon stretching ahead and seabirds soaring above — it is still nearly impossible to picture the diverse and abundant life that hides beneath the waves.

But occasionally, you get a glimpse.

A humpback whale breaches off the bow. Three sea lions mingle in a group before diving in unison. A pod of 100 or more dolphins puts on an acrobatic show, its members leaping above the surface two or three at a time.

What sounds do such marine mammals hear, and how loud is it in their underwater world?

Those are the questions driving scientist Danielle Lipski and her colleagues, who were on a daylong voyage Thursday out of Bodega Bay on a 67-foot ship — Research Vessel Fulmar — to deploy what amounts to a large listening device meant to record the ocean’s sounds.

Marine zoologists are increasingly worried that an ever-louder ocean — traversed by fishing vessels, shipping traffic and military craft — might interfere with the songs and vocalizations that whales and other marine mammals use to communicate about food sources, migratory routes, reproductive availability and other critical functions.

(To listen to recordings of whale songs, click here and here.)

The experiment by Lipski and her crew will last two years, with hopes the newly placed hydrophone picks up sounds from passing cetaceans, including whales and dolphins, as well as noise from passing ships.

The resulting “soundscape” could help scientists determine what steps people might take to protect the sanctuary’s marine mammals.

“In general, we know that shipping traffic has increased over the past several decades,” said Lipski, research coordinator for the Cordell Bank National Marine Sanctuary.

“There’s gotten to be more ships and bigger ships,” both factors that increase noise, she said.

The listening station launched Thursday is one of 11 spaced around the North American continent, part of the Ocean Noise Reference Station Network operated by the National Oceanic and Atmospheric Administration. It does not allow real-time listening to the sounds of the ocean, but rather makes recordings.

Other devices are located off both coasts, in the Gulf of Mexico and in the Arctic Ocean off Alaska, as well as off the Hawaiian Islands and American Samoa.

Whales and dolphins use sounds as their primary way to communicate in an otherwise dark world, so extra, man-made noise in the ocean can at the very least interfere with their communication, said Samara Haver, a graduate research assistant with the Oregon State University Research Collective for Applied Acoustics, which is partnering with Lipski on the project.

Studies also indicate noise increases stress, Haver said, creating “kind of a suite of negative effects” on the animals.

What scientists know from their work so far is that whales may be forced, at a minimum, to alter or amplify their communication in the same way someone at a loud cocktail party might raise his voice to be heard.

The listening device deployed by Lipski will measure sound in what happens to be one of the most important cocktail parties for ocean wildlife in the world.

The Cordell Bank National Marine Sanctuary, a nearly 1,300-square-mile area offshore from southern Sonoma County and Point Reyes, is considered among the richest feeding grounds for marine wildlife on the planet. The area owes its productivity to the upwelling of cold water off Point Arena that brings nutrients toward the surface, where hundreds of species can partake.

Cordell Bank is one of three adjoining national marine sanctuaries that form a contiguous band of protected waters along 300 miles of California coast.

All three marine sanctuaries — including Monterey Bay and Greater Farallones — are traversed by shipping lanes in and out of San Francisco Bay, and some overlap whale environments.

Up to 4,500 large ships come and go from the bay each year, Lipski said, while the worldwide commercial shipping fleet has approximately tripled over the past 50 years.

In the Cordell Bank sanctuary, that traffic stands to affect at least 20 species of marine mammals that live or feed in the area, including 13 species of whales, dolphins and porpoises.

The main species include blue, humpback and fin whales — all listed as endangered species — and gray whales, Lipski said.

Sperm and minke whales also are thought to be in the area but aren’t spotted often, she said.

To record the leviathans and shipping traffic, scientists use carefully calibrated, heavy-duty technology — instruments built to withstand the beating of two years in the ocean.

Captain Chris Eubank had taken the research ship 35 miles southwest of Bodega Bay on Thursday and was just shy of the destination coordinates when Lipski and Dale Hubbard, a technician from Oregon State, prepared the gear for delivery to the ocean floor.

The recording site was selected because of the ocean depth — more than 1,700 feet — the soft sediment floor and the relatively nonexistent slope. It also is outside areas open to fishing trawlers, thus minimizing the risk of the equipment being dragged across the ocean floor.

First, the crew deployed a 700-pound foam buoy that was let out behind the boat on a long line.

The hydrophone — a 5-foot-long metal cylinder — was tethered to a connecting device and suspended from the massive buoy so it would be submerged hundreds of yards below the ocean surface.

Then the crew used a winch to slide a rusted 800-pound train wheel overboard to anchor the whole contraption to the ocean floor. The wheel made barely a splash when it hit the water, sinking slowly until the attached buoy dropped a few inches below the surface and then disappeared entirely.

“Good job, everybody,” Eubank said. “Perfect.”

When scientists come back to retrieve the hydrophone in two years, a radio signal will release the equipment from the anchor and it will float to the surface for recovery.

Lipski said the entire undertaking cost about $70,000, including about $40,000 from the International Fund for Animal Welfare.

You can reach Staff Writer Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.

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