By Carina Stanton Wednesday, July 13, 2005 Scientists suspect that rising ocean temperatures and dwindling plankton populations are behind a growing number of seabird deaths, reports of fewer salmon and other anomalies along the West Coast. Coastal ocean temperatures are 2 to 5 degrees above normal, apparently caused by a lack of upwelling — a process that brings cold, nutrient-rich water to the surface and jump-starts the marine food chain.
Upwelling fuels algae and shrimplike krill populations that feed small fish, which provide an important food source for a variety of sea life, from salmon to sea birds and marine mammals. "Something big is going on out there," said Julia Parrish, an associate professor in the School of Aquatic Fisheries and Sciences at the University of Washington. "I'm left with no obvious smoking gun, but birds are a good signal because they feed high up on the food chain." This spring, scientists reported a record number of dead seabirds washed up on beaches along the Pacific Coast, from central California to British Columbia. In Washington, the highest numbers of dead seabirds — particularly Brandt's cormorants and common murres — were found along the southern coast at Ocean Shores. Bird surveyors in May typically find an average of one dead Brandt's cormorant every 34 miles of beach. But this year, cormorant deaths averaged one every eight-tenths of a mile, according to data gathered by volunteers with the Coastal Observation and Seabird Survey Team, which Parrish has directed since 2000. "This is somewhere between five and 10 times the highest number of bird deaths we've seen before," she said. Parrish expects June figures to show a similar trend. Upwelling is fueled by northerly winds that sweep out near-shore waters and bring cold water to the surface. "You can think of it like a cup of coffee," Parrish explained. "When you pour in cold cream and then blow across the cup, the cream rises up from the bottom." But this spring's cool, wet weather brought southwesterly winds to coastal areas and very little northerly winds, said Nathan Mantua, a research scientist with the Climate Impacts Group at the University of Washington.
And without upwelling, high-fat plankton such as krill stay at lower depths. "In 50 years, this has never happened," said Bill Peterson, an oceanographer with the National Oceanic and Atmospheric Administration (NOAA) in Newport, Ore. "If this continues, we will have a food chain that is basically impoverished from the very lowest levels. Salmon surveysNOAA's June and July surveys of juvenile salmon off the coasts of Oregon, Washington and British Columbia indicate a 20 to 30 percent drop in populations, compared with surveys from 1998-2004, especially coho and chinook.
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"We don't really know that this will cause bad returns. The runs this year haven't been horrible, but below average," said Ed Casillas, program manager of Estuarine and Ocean Ecology at NOAA's Northwest Fisheries Science Center in Seattle. "The take-away message is that we are seeing unusual conditions so we need to be cautious with returns for the next one to four years," he said. "Managers need to put enough time, people and money on the ocean side of the question." This spring, scientists began tracking anomalies along Washington's coast, from the appearance of warm-water plankton species to scores of jellyfish piling up on beaches. A Guadalupe fur seal, native to South America, was found dead in Ocean Shores. Parrish is documenting unusual breeding behavior among common murres on Tatoosh Island off the Olympic Peninsula. In 15 years of monitoring the murre colony, this is the latest the birds have initiated breeding. "They are starting very, very late and then just giving up," she said. Seabirds are also showing signs of stress in California, said Bill Sydeman, director of marine ecology at Point Reyes Bird Observatory. Sydeman monitors a colony of Cassin's auklets in the Farallon Islands, west of San Francisco. This spring's breeding season was a month late, Sydeman said. Less than half the colony tried to nest in April and then abandoned the colony by June. "We have been monitoring this colony for 35 years. Never before have we seen colony abandonment," he said. "Nobody saw this coming." Sydeman and Parrish point to starvation stress as the cause for decreased breeding and increased bird deaths, especially among the cormorants, murres and auklets. Signs of stress Studies of dead birds in May on California beaches found emaciated bodies, with atrophied muscles and empty stomachs, said Hannah Nevins, a beached-bird survey coordinator at the Moss Landing Marine Lab in Northern California. "Spring is when the food comes in," Nevins said. "When you have a really strong, persistent upwelling wind, it creates a conveyor belt of food, but the wind is slacking this year." Mantua, the UW research scientist, tracks ocean temperatures and climate conditions to understand changes in currents and wind patterns. This year he found temperatures 2 to 5 degrees above normal — readings typically seen during an El Niño. But this is not an El Niño year, he said. The trend toward warmer temperatures began in fall 2002, said Peterson, the NOAA oceanographer. No one is pointing to one direct cause for the warmer waters, but many scientists suspect climate change may be involved. While Peterson is concerned about the unusual ocean conditions, he is more worried that people will not take notice. "People have to realize that things are connected — the state of coastal temperatures and plankton populations are connected to larger issues like Pacific salmon populations," he said. Scientists say animals along the Pacific Coast have managed to overcome changing environmental conditions for many years. "All of these species are very long-lived," Parrish said. "They can die in big numbers for a year or two without severe impact to the populations." But, she cautioned, human activity could jeopardize the survival of animals already stressed by environmental changes. "This, for instance, would be a truly bad year for an oil spill." Additional ResourcesOcean Surface Topography from Space-Science Pacific Decadal Oscillations packs a one-two punch How you can helpScientists want to know when dead animals wash up along Washington's beaches. To report marine mammals, call the NOAA fisheries marine-mammal strandings hotline at 206-526-6733. To report birds, contact the Coastal Observation and Seabird Survey Team at 206-221-6893 Copyright © 2005 The Seattle Times Company Source: Seattle Times Company |
