BREMERTON – Deposits at the bottom of Hood Canal suggest a natural cycle of high and low oxygen levels, and the last 50 years have been on the high side despite recent fish kills, according to a recent unpublished study.
The study done by the Battelle Marine Science Laboratory in Sequim could shed light on recent fish die-offs in the glacier-gouged fjord between the Kitsap and Olympic peninsulas, the Kitsap Sun reported Wednesday.
The principal scientists in the research, Eric Crecelius and Jill Brandenberger, told the newspaper that 10-foot core samples of sediment from the floor of the canal north of Hoodsport indicate oxygen levels in the water have generally been very low in the early 1700s, 1800s and 1900s and high in the latter part each century.
A low-oxygen period also apparently occurred in the main channel of Puget Sound in the mid-1800s but was “not as dramatic,” Crecelius said.
Natural sediment mixing prevented researchers from reaching conclusions for periods less than 10 to 20 years, he and Brandenberger said.
The study did not indicate whether fish kills have been associated with low-oxygen periods in the cycle, Crecelius said.
“At this point, we can’t say how important is man’s input to Hood Canal, in addition to the natural cycle,” he added. “Man should make an effort to reduce nutrient inputs because many other studies show how (they) cause low oxygen in many water bodies.”
The findings could mean “that the system in Hood Canal is in a delicate balance and that any additional input from man can upset that balance.” Brandenberger said.
The research, which have not been published in a scientific journal, likely provides answers to only part of the puzzle, said Jan Newton, a University of Washington oceanographer who is leading a multimillion dollar study of currents, weather, plankton growth, ocean conditions, river flows and other factors affecting Hood Canal.
“There are many mechanisms that can cause hypoxia (low oxygen), and it is difficult for us to know what was causing it in the 1800s,” Newton said.
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