Marine Life Suffering as Coast Warms

Steadily warming ocean water is devastating marine life along the coast of California--from microscopic plankton and forests of kelp to the fish, birds and mammals that depend on them for sustenance, researchers at the Scripps Institution of Oceanography said Thursday.

The researchers, who studied extensive water temperature records dating to 1916, documented an overall temperature increase of 2 degrees Fahrenheit in coastal waters along the length of the West Coast in recent decades. This has occurred even as the incidence of more extreme ocean warming events such as the El Nino currents also increased significantly.

The new blanket of warmer water is, in a sense, slowly smothering ocean life by preventing more fertile, deep Pacific currents from rising to the surface, the researchers said. This blocks the source of nourishment for the rich menagerie of marine life for which the West Coast is known.

The warmer waters also enable fish and animals to migrate northward from tropical waters and edge out California’s native species.

So far, the researchers are not sure whether their findings are evidence of global warming induced by human influences--such as the effect of greenhouse gasses--or of the more natural, slow rhythms of the Pacific climate.

There is some evidence to suggest that it may be a cyclical pattern--in which case many species may once again thrive--but the long-term prognosis for marine life along the West Coast is not known.

“There is a new average temperature for the California Current,” said research oceanographer John A. McGowan, a co-author of the study, which is published today in the journal Science. “On the face of it, 2 degrees does not seem like much, but it has had very profound effects in the ecosystem of the California Current and the Gulf of Alaska, and, I suspect, the entire eastern half of the Pacific.”

By looking at records from 17 coastal monitoring stations between La Jolla and Charleston, Ore., McGowan, with Scripps colleagues Daniel R. Cayan and LeRoy M. Dorman, determined that the recent warming trend began in 1977. It was around that time that climate researchers began documenting major changes in weather patterns in the northern Pacific region.

In the same year that those average sea surface temperatures started to climb throughout the 200-mile-wide corridor of the California Current, the levels of plankton declined by about 70% and have not recovered during the last 20 years. The decline in plankton, which form the basis of the marine food chain, almost certainly in turn had severe consequences for many larger species that directly or indirectly depend on them.

“Abalone have virtually disappeared. Squid are at almost zero,” McGowan said. “The Chinook salmon are almost gone. Anchovy are unfishable. Kelp beds have been greatly diminished.” Some species of seabirds, once present by the millions along the coastline, have virtually vanished.

Over the last two decades, commercial fishing has also increased dramatically, as have a range of environmental stresses--from the chemistry of waste runoff to the prevalence of underwater noise. So it is difficult to sort out the various threads of cause and effect when assigning responsibility for the declining health of coastal marine life, McGowan cautioned.

“This temperature change, we believe, has resulted in an overall decline of primary productivity,” he said. “That should have effects throughout the entire food web. There is scattered evidence that indeed this is what we are seeing.

“It is enough to make you worry,” he said.

The records suggest that the California current has experienced a dozen similar warm spells since 1916, the year that researchers started monitoring water temperatures off the Scripps pier in La Jolla.

There have also been at least 10 cold spells, the records show.

The warming water appears to occur simultaneously up and down the coast, rather than beginning near the equator and moving northward as previously thought.

The researchers suspect that the frequency of these shifts, with their profound consequences for marine life, is increasing, along with the overall average water temperature. But they aren’t sure why.

“For the ocean marine environment, the change is very significant and the temperature is an index of something large scale. That much is clear,” said Cayan, director of the Scripps climate research division. “And there are those who think this is just the way the climate should react to a greenhouse-warmed earth.

“But I am not at all sure,” Cayan said. “My hunch is that what we are seeing is an expression of the natural variability of the Pacific basin.”