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"Researchers examining what long-term data are available have uncovered alarming and portentous evidence of a changing world. One area where monitoring has been funded is in the southern portion of the California Current, a 600-mile-wide swath of southward-flowing water running along the western U.S. coastline, roughly from Oregon down through California. Part of a great subtropical gyre of currents in the northern Pacific Ocean, the California Current is the eastern end of a swirling seawater highway that circles from Japan to Oregon, south past California just into Mexico, across to the Philippines, and back up to Japan to begin again. Along the way the water changes. As it crosses the Pacific toward North America, more water comes in through rain than leaves through evaporation, so the overall current becomes less salty. As it comes down the U.S. coastline, it meets cold, salty water heading north on another current, mixing in great meanders and eddies that can be up to 300 miles wide. The current turns west again south of California to start the process again.
In 1949, a combination of state and federal organizations began monitoring physical, chemical, biological, and meteorological facets of the California Current under the auspices of the California Cooperative Oceanic and Fisheries Investigations program, known as CalCOFI. It was designed in part to track many factors affecting commercially important fish species such as mackerel and sardines. The data gathered under CalCOFI include air temperatures, wind speeds, nutrient levels, salinity, water temperature on the surface and deep below the surface, and the abundance of larval fish and zooplankton -- the smallest marine animals. The early monitoring cruises brought researchers as far north as the Oregon border, but the surveys were scaled down to meet budget demands in 1970. But those first 20 years of data were enough to show that what happens in the south and what happens in the north tend to be the same. The data since 1970 cover the area between San Diego and Santa Barbara. It is the largest, longest-term data set of its kind on the West Coast.
What happens if you watch those data change over the years? Your findings might echo those of John McGowan, an oceanography professor at the Scripps Institution of Oceanography in San Diego: As water temperatures have risen, the base of the marine food chain off the coast of California has crashed. And one by one, the fish and birds farther up that food chain are crashing, too. Life in the ocean begins with tiny plants known as phytoplankton. Like all plants, phytoplankton need light to drive photosynthesis and nutrients to feed the process. Although it is somewhat counterintuitive, the richest and most nutritive ocean waters are the coldest and heaviest. Strong winds do the work of stirring the system and pulling the nutrient-rich waters up toward the light.
The first problems showed up in conjunction with El Niños, shortterm changes in ocean temperatures that tend to increase the warm water along the western U.S. coastline, reducing the food that boosts the phytoplankton. But researchers like McGowan noticed a difference between early El Niños and the later ones. Numbers of zooplankton -- the tiniest animals in the food chain, which depend on the phytoplankton -- dropped during the El Niño of 1957 to 1959 and then quickly rebounded. But after subsequent El Niños during the 1983 to 1984 and 1997 to 1998 seasons, the zooplankton did not come back. In 1995, going back through the accumulated years of data, McGowan reported a staggering finding in Science: Zooplankton numbers in the California Current had dropped by 70 percent. The CalCOFI data show a sharp increase in California Current water temperatures in 1977 -- at the same time the zooplankton numbers crashed. "It's the largest change ever measured in plankton productivity in the ocean," McGowan says. "This enormous change in the zooplankton in the California Current could not be detected from year to year. It several decades before we discovered this big drop, by at least 70 percent or even up to 80 percent."
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http://www.tidepool.org/original_content.cfm?articleid=138191
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