From wind to whales

Scientists untangle the Monterey Bay's food web

It's well before dawn at Moss Landing Harbor, and the research vessel John H. Martin has already taken on passengers for a day cruise around Monterey Bay.

Bundled in polar fleece and clutching steaming mugs of coffee, they've brought binoculars and big chunks of Ghirardelli chocolate to keep up their strength. And while they plan to do their share of whale watching, they are not your average sanctuary sightseers. Hunkered down in the main cabin among laptops and cloth-bound notebooks, these marine scientists are working on a project that will eventually uncover why the waters of the Monterey Bay attract one of the most spectacular aggregations of marine birds and mammals in the world.

But today's goals are more mundane. Skipper Lee Bradford will pilot the boat 13 miles due west and begin driving straight lines that will take the scientists clear across the width of Monterey Bay and almost down to the Monterey Peninsula. From above, it looks as if he were mowing the waves in neat rows miles apart.

Along the way, observers atop the ship's flying bridge make a note of the marine mammals and birds they spot. Periodically the scientists lower giant, fine-mesh butterfly nets 200 meters down to collect plankton, water samples and take temperature and salinity readings. It's an unusual marriage of physical oceanography--concerned with ocean currents and temperatures--and biology.

They often spend 12-hour days on the water to get the most bang for each trip buck. Boat time for the monthly two-day surveys runs in the neighborhood of $3,000.

Friday's cruise was one small part of a multi-year effort to monitor the ecosystem of the Monterey Bay National Marine Sanctuary. Since 1997, scientists have cruised the bay once a month to learn how the water temperature and chemistry affects populations of plankton and ultimately the numbers of large animals such as birds and whales.

"We want to find out how birds and mammals respond to those indirect correlations, since they don't actually eat the plankton or the water," said Don Croll, assistant professor of marine biology at the University of California, Santa Cruz.

What the scientists know so far is this: In spring, winds from the northwest blow warm surface waters off the California coast to the southeast, pulling cold water up from the depths like a vacuum. Rich in nitrates and phosphates, the upwelling water works like Miracle Gro on a garden, helping the populations of photosynthetic plankton to double in mass in less than 24 hours. Tiny ocean grazers such as krill gorge themselves and take advantage of the good times to breed.

The dense summertime clouds of krill draw big predators such as whales, seabirds and seals by the thousands.

"These upwelling systems comprise a very small part of the whole world's oceans, less than 1 percent, yet they produce up to 50 percent of the world's fisheries," said Baldo Marinovic, a research biologist at UC-Santa Cruz. Those fisheries include seven of the 10 most valuable commercial nearshore fisheries in California.

Upwelling is a relatively rare phenomenon. Only the coasts of California, Namibia and South Africa, and Chile and Peru have similar systems. Within California, the Mendocino coast, the Farallon Islands, the Channel Islands and Monterey Bay near Ano Nuevo Island are the primary upwelling hotspots.

Scott Benson, a graduate student at Moss Landing Marine Laboratories, summarizes the project another way. "We call the program 'from wind to water' because we're trying to understand the biology between the wind blowing and the whales showing up."

Some of the work will help biologists predict and manage populations of the endangered blue whale.

"Historically, the approach has been to manage species. But to do that, you must understand the habitat and how the species is integrated into the entire ecosystem," Marinovic said.

As the largest predators on earth, whales have the ability to store vast amounts of food and travel great distances. That's ideal for an animal that feeds on dense patches of prey that are only available for part of the year and can be located hundreds of miles apart. For example, during fall the winds that drive upwelling can suddenly stop, halting local plankton productivity instantly.

"If the Monterey Bay system is shutting down, maybe the Channel Islands will turn on. They don't know exactly where the productivity is, but they'll look. If there's nothing at Safeway, try Nob Hill," Croll quipped.

Although they generally stick to areas with colder waters, the whales still surprise biologists. The 1997-98 El Nino brought warm and relatively unproductive waters to California, yet record numbers of whales converged on Monterey Bay to feed.

"Even though the productivity here was lower, it was the only place offshore in California where there was any productivity. So even through the restaurant was not serving a great menu, they came because it was the only place to eat," Marinovic said.

During the two-day October cruise, observers saw only two whales, a humpback and a blue. Compare that to the 21 blues and 24 humpbacks they spotted just two months ago. In the larger scheme of things, said Marinovic, numbers like that mean "this is shaping up to be more of a typical year, where we had high productivity in the spring that persisted until September."

Even the birds matched the scientists' expectations given the water conditions. The sooty shearwaters that flock here by the thousands in summer to feed on krill were gone, replaced by Buller's and black-vented shearwaters that target warm-water bait fish.

On Friday, the boat took a detour so everyone could marvel at the steel-gray dorsal fin and colossal size of a blue whale.

"We rely on volunteer observers, mostly students and ex-students, who have experience identifying marine mammals and birds. So when there's an opportunity to see a blue, we take a few minutes to go over and look at it," Croll said.

This year, project scientists have begun making similar survey cruises near the Channel Islands to see if Monterey Bay's patterns hold true for other upwelling sites.

The group plans to hold the surveys year-round within the next several years as the Monterey Bay National Marine Sanctuary gears up its program to monitor on the heartbeat of the bay.

--Kathleen M. Wong