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Staff Accomplishments

Getting to the Core of the Hypoxia Problem in Washington's Hood Canal

June 2007
Research team shows cyclic nature of low-oxygen periods in waterway Growing concern over low dissolved oxygen concentrations over the last 50 years in Hood Canal, a fjord in Washington State, reached a new peak when massive fish kills occurred in 2002 and 2003. A new study led by Pacific Northwest National Laboratory found low oxygen levels recorded in Hood Canal sediment dating back over 400 years are influenced by century level climatic cycles in the North Pacific Ocean. Low levels of oxygen, a condition known as hypoxia, can stress or kill resident organisms. The impact can be severe, leading to extensive "dead zones" that impact commercially, recreationally and ecologically important fish and shellfish. "Over the last 400 years, there have been hypoxia events during each century in Hood Canal," said Pacific Northwest National Laboratory Fellow and co-principal investigator Eric Crecelius. The team discovered a cycle of low-oxygen events in the early 1700s, early 1800s, and early 1900s. The current trend shows that conditions conducive to low oxygen levels are returning to Hood Canal. Finding Evidence at the Bottom of Hood Canal As part of their ongoing efforts to understand hypoxia, the National Oceanic and Atmospheric Administration (NOAA) looked to Hood Canal. This deep fjord does not follow the typical pattern of hypoxic events in the Gulf of Mexico and other areas. For this half-million dollar, multi-year NOAA study, the researchers sampled sediments from the central and southern parts of Hood Canal. The sediments were removed as 10-foot-deep cores. "This was the first time deep core sampling has been done in southern Hood Canal," said Crecelius. The southern tip of the Canal is about a 45-minute drive north on Highway 101 from Olympia. Analyzing the Clues Left in the Sediment "Our research indicates Hood Canal's hypoxic events are a natural process," said PNNL scientist and co-principal investigator Jill Brandenberger. The research shows a good correlation between the timing of the hypoxic events in Hood Canal and regularly occurring shifts in oceanographic conditions of the North Pacific Ocean over the last 400 years. By analyzing multiple tracers in the samples, the researchers reconstructed the waterway's history from pre-European settlement to the late 1900s. The levels of some tracers indicated certain activities that could be matched to historical events, such as the Industrial Revolution. Researchers at Texas A&M University measured isotopes of carbon and nitrogen to determine the sources of these elements from marine plankton or land plants. To help establish the timeline and look at the connection between logging and hypoxia, University of Washington scientists studied alder pollen at different ages of the sediment. Alder trees grow in the place of clear cut evergreen forests. To examine hypoxia, PNNL scientists studied several trace metals that precipitate and accumulate when oxygen levels are low. Further, microfossils of plankton unlock clues about nutrient levels. By determining the plankton species present in the Canal over the centuries, researchers at Bryn Athyn College and the U.S. Geological Survey could relate changes in the plankton community to human activities. The Human Factor "Certainly humans have contributed to the extent of the events, but there were events long before European settlement," said Brandenberger. "However, humans should do what they can to reduce future hypoxic events severity and intensity." For example, people living near waterways can reduce the amount of chemicals they add to the water. Avoid adding toxic materials, such as antifreeze and motor oil from automobiles, through regular automotive tune-ups. Avoid over-fertilizing lawns and shrubs, as run-off from lawns can supply nitrogen to promote algal blooms. The data from these and related studies by NOAA's Coastal Hypoxia Research Program will be used to develop advanced techniques for measuring hypoxia in ocean waters, estuaries and the Great Lakes. For more information, contact Charlie Brandt, Resource and Ecosystem Management Product Line Manager, Pacific Northwest National Laboratory or Jill Brandenberger, Co-Principal Investigator.

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