Low Oxygen Levels Threaten Life in Hood Canal

By Alice Shieh

(View of Hood Canal at sunset.)

Hood Canal is a 70+ mile long waterway that separates Kitsap Peninsula from Olympic Peninsula. It's actually a fjord--the only one on the west coast--and words to describe its scenery are: serene, beautiful, and picturesque. Personally, it's one of my favorite places and I think it's gorgeous. However, back in 2003, major concerns were raised regarding low oxygen levels in Hood Canal's waters--levels so low that the event was considered historic. What resulted was an alarming loss of marine life.

The Seattle Post Intelligencer ( http://seattlepi.nwsource.com/local/139800_hood16.html ) reported that, because of low oxygen levels at deeper depths, octopus mothers were abandoning their eggs and deep-dwelling marine creatures were being spotted at shallow depths. Fishing was banned that year in the canal--a historic first. I remember that, in the months following, then-Governor Gary Locke appeared in numerous television ads to warn of the threat to Hood Canal marine life and warn against pollution in its waters. (I live in Kitsap County, so it may have only aired in areas surrounding Hood Canal.)

Hood canal is an important source of Northwest seafood. It homes oysters, clams, Dungeness crab, cod, salmon, shrimp, squid, octopus, and scallops. Therefore, the deaths of marine life in Hood Canal were considered a crisis, as it provides much of the seafood that makes Seattle famous. (A local diver describes the underwater graveyard she saw during this time in this article: http://www.cdnn.info/news/eco/e060923b.html ) Furthermore, Hood Canal provides food not only for western Washington, but for the wildlife that depend upon it for survival. Numerous bird species (including the bald eagle, which hunts fish), bears, deer, sea lions, otters, and many more creatures inhabit the banks of the fjord. Even whale pods have been known to visit its waters. Hood Canal is both a source of the seafood that is iconic to the Pacific Northwest, as well as the source of life for many threatened species of wildlife.

Early reports, such as this one from CDNN Eco News, blamed human pollution for the mass deaths: http://www.cdnn.info/eco/e040506/e040506.html For example, the article claims that "Auto emissions (washed down by rain), lawn fertilizers, sewage, and storm water runoff all feed nitrogen and other nutrients into the water. The nutrients generate plankton blooms, which die after a few days, sinking to the bottom, where decomposition uses up oxygen. The lack of oxygen kills fish and sea plants, which decompose and use up most of the remaining oxygen."

Hood Canal Dissolved Oxygen Program's online brochure explains why the fjord is prone having pockets of low oxygen:

"The geology and bathymetry (underwater topography) of Hood Canal play a large role in the water quality and dynamics of how the water moves. The entrance to the canal is relatively shallow, about 150’. Just south of the entrance the canal becomes very deep, to 500 and 600’. This ‘sill’ at the entrance creates a condition in the canal that doesn’t allow the water to flow or exchange very easily with the changing tides and seasons. The ‘sill’ tends to retain the water (reduces the exchange) in the canal and estimates of complete water exchange rates are in the magnitude of years.

"The water of Hood Canal can be highly stratified… which means there is an upper layer of different temperature and salinity (saltiness). Highly stratified water doesn’t mix very well. So, essentially, the waters of Hood Canal are deep, stratified, and exchange very slowly. This is not a good situation when considering the resilience of Hood Canal to human contributions." http://www.hoodcanal.washington.edu/aboutHC/brochure.html

Since the waters don't mix well, pockets of low-oxygen water tend to form in Hood Canal. This worsens when large amounts of plankton form and settle to the sea floor to die, depleting the existing oxygen supply during decomposition. While human interaction with Hood Canal's ecosystem were originally blamed for the low oxygen levels, more recent research has identified natural causes for the phenomenon. Water circulation within the canal, the amount of ocean water it receives from the Pacific ocean, and plankton growth all contribute to (or take away from) the oxygen levels in Hood Canal. While this doesn't exonerate human contamination, it does mean that pollution results in the oxygen crisis only when conditions weaken the natural resiliency of Hood Canal. ( http://www.kitsapsun.com/news/2007/nov/27/oxygen-levels-keep-hood-canal-fish-research/ )

The 2002-2003 loss of marine life in Hood Canal sent both environmentalists and politicians in an uproar. Many politicians pointed fingers at human pollution before scientists had even finished their studies. Now, natural causes for the low oxygen pockets have been identified by the scientific community. More than just a local foods issue, this is also an example of discourse in the making. The problem has never changed, but it has been framed and reframed differently within the last five years.