IN SEARCH OF THE BIG PICTURE

A better understanding of the California Current could enable scientific advancements such as improved weather forecasting for the western United States and the implementation of measures to ensure the survival of key marine populations in the region. The marine creatures living here are a bellwether when it comes to climate-change effects. The tip-off that indicates a major shift in ocean temperature or circulation might be a sudden drop-off in the population of a certain species of zooplankton, the rapid swelling in numbers of a certain type of seabird, or the migration of a fish species. The LTER scientists want to test a variety of theories that explain how these physical changes play out.

"The California Current is intrinsically interesting but also extremely important for marine resources," said Mark Ohman, Scripps's LTER principal scientist. "In order to properly manage marine ecosystems in the long term, we have to be able to understand the natural sources of variability and tease those apart from anthropogenic causes."

Phillip Taylor, the NSF program director whose program scientists recommended the California Current site for inclusion in the LTER network, said Scripps's program is in the mold of long-term field studies taking place in Hawaii and Bermuda. In those places, the benefits of comprehensive data gathering have exceeded expectations.

"When we study things over longer terms and at higher frequencies, we are continually surprised at the way things happen," he said.

This LTER network site will take the form of a hypothesis-driven series of experiments with less of an emphasis on steady recordkeeping. Still, participating California Current Ecosystem investigators will draw heavily from CalCOFI, an expansive observation program nearing its seventh decade.

The mystery of vanishing sardines had initially launched CalCOFI, which exposed much of the climatic subtext of ecosystem change that fascinates the LTER team today. CalCOFI survey runs began in 1949, a decade after the beginning of one of the most profound industry collapses in the country's history. Fishing fleets, canneries, and wholesalers on the West Coast all reeled from the inexplicable loss of a fish species thought to be in limitless supply.

An early and obvious culprit was overfishing. But as CalCOFI proved over the ensuing decades, placing blame on the sardine industry wasn't that simple. The collapse had come at a time when fishing methods were becoming too efficient for their own good, but there was another cause, a far subtler trend playing out in the ocean itself. A climate signal called the Pacific Decadal Oscillation (PDO) was entering its negative phase, a fluctuation marked by generally colder ocean temperatures and lower sea-surface heights in the eastern Pacific Ocean.

The altered set of physical conditions set in motion a corresponding set of biological conditions. The cold water allowed certain species of zooplankton to thrive while concentrations of others diminished. The change worked its way through the food web, affecting the success of larger predators to find food and reproduce. The PDO cold phase lasted until the mid-1970s, ushered out by some of the driest years in southern California history. Strict catch limits for fishermen and the returning pendulum of nature eventually saw a return of sardine populations after a warm PDO phase began.

If it hadn't been for CalCOFI's steady measurements throughout the course of the entire cycle, scientists would have had a much harder time understanding the connections between overfishing and the natural phase of decline of the sardines as the marine ecosystem changed. The California Current LTER project hopes to transcend the fisheries oceanography of CalCOFI by augmenting basic measurements with experiments. Instead of merely estimating the abundance of certain marine phytoplankton, for instance, researchers will fashion experiments to plot the rate at which grazers selectively consume that type of phytoplankton.

"We have key hypotheses that we've been able to develop from distilling decades of research, and we now intend to test those hypotheses," Ohman said.

Think of climate trends like the PDO, El Niño, and human-caused warming as the gas powering the California Current. Now LTER scientists want to look inside the engine compartment to see which physical forces control biological responses to that power.

"It's been a dream to look at the whole system," said Ralf Goericke, coprincipal scientist. "Ever since I came to Scripps 11 years ago, I've wanted to be part of a group that could take the whole ecosystem and study its components together."

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