UNDERSTANDING THE BASICS

Researchers know that physical properties of the ocean affect the biology of the California Current, but which ones are most important and when? The main physical parameters studied in most LTER experiments will be factors like ocean currents, the amount of thermal stratification between warm surface and cool deeper layers in the water column, and the rate of upwelling of deep, nutrient-rich waters toward the surface. These processes alter the types and growth rates of phytoplankton (primary producers), whose fluxes have a ripple effect through the rest of the food web.

Specifically, says Ohman, researchers want to know the relative effects of four basic processes—the main flow of the California Current, the cross-shore flows between the coast and the deep ocean, the rate of supply of nutrients from deep waters, and the top-down pressures that come from predators. In an unknown combination, these factors cause shifts in the composition of small organisms at the base of the food web. Click on "Krill vs. Krill" to view the animation.

To understand these mechanisms, LTER oceanographers are developing new, sophisticated data-gathering abilities. Goericke and Mike Landry are able to more rapidly identify and quantify particular types of plankton using techniques of flow cytometry and High-Performance Liquid Chromatography. Satellite remote-sensing specialists, Greg Mitchell and Mati Kahru, are developing new computer algorithms to obtain high-resolution images of phytoplankton blooms from space. David Checkley is using a Laser Optical Plankton Counter to rapidly assess the size, composition, and vertical distribution of zooplankton. Katherine Barbeau's lab is testing the possibility that phytoplankton become iron-starved as newly upwelled water begins to age. And Lihini Aluwihare's group is trying to understand the complex organic compounds that constitute the large reservoir of dissolved organic matter in the California Current. The Spray glider developed at Scripps will send continuous robotic observations of the California Current back to Scripps via satellite. Amassing all of these data will be computer modelers who will attempt to simulate the mechanics of the California Current and estimate what changes occur under different climate scenarios. (See A Model Ecosystem)

As your stockbroker will tell you, past performance is no guarantee of future results, and so it goes with the waters off California's coast, which have experienced a steady anthropogenic temperature increase over the course of CalCOFI's long history. Ohman notes that no one yet knows what will happen during the next climatic perfect storm, the "triple-positive" year in which the PDO and El Niño peak at the same time while superimposed on an ever-warming ocean.

"When El Niño next occurs in the positive phase of the PDO, following decades of ocean warming, will it have the same consequences El Niño had in a positive phase of the PDO 50 years earlier when the whole background state of the ocean was cooler?" Ohman asked. "We probably have better prospects of sorting out such questions here in the California Current than anywhere in the ocean because of the excellent foundation of CalCOFI observations."

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