Death in the Canal: A Who Done It
by Chuck Louch, PTMSC Docent
The Hood Canal is one of about 30 man-made marine dead zones in the world. These differ in details but all have a common feature, that of oxygen depletion caused by high nutrient levels in the water. The most important of these nutrients is nitrogen, in the form of nitrate that must be available for all healthy plant growth. High concentrations of nitrates in bodies of water lead to dense populations of planktonic green algae. These may initially raise oxygen levels in surface waters through photosynthesis but as they die, sink to lower levels, and decay these algae will deplete the oxygen in the depths.
Hood Canal is ideally suited for the production of dead zones since it is a long, narrow inlet that is quite deep in some parts. Hydrologically speaking it is a two-layered system. The surface water is less saline and thus less dense than that of Admiralty Inlet because of runoff from streams and rivers, septic systems, etc. This water tends to move northward towards the entrance of the canal. At the same time dense seawater from Admiralty Inlet flows southward into Hood Canal under the less saline surface water. But there is some mixing of water at the interface between the two layers so that some surface water pollutants tend to stay, or flow back into the Hood Canal rather than moving towards the sea.
Also, although there are significant tides in The Hood Canal they are not great enough to clear the Canal at each change so that, in the southern part of the Canal at least, the water just sloshes back and forth. For these reasons the Hood Canal flushes itself out relatively slowly, only once in a year according to one estimate.
I should emphasize that the above is a very simplified picture of a very complex system that can change with changing meteorological conditions. Drought, for instance can reduce the amount of freshwater entering the canal and an el Nino could warm the ocean waters entering the canal thus changing patterns of water movement. Strong south winds may push the surface waters out of the canal more rapidly than usual causing some upwelling of deep, more saline, waters.
The Hood Canal extends through three counties, Mason, Kitsap, and Jefferson, that have an aggregate population of about 310,000 people, up from about 19,000 in 1980. Of these about 50,000 live in the Hood Canal watershed. In the past most of the dwellings along the Canal were weekend cottages or cabins that stood empty much of the time. But now, many people make their homes in the area and commute to Olympia, Tacoma, Bremerton, or even Seattle. As a consequence more homes are occupied year-round, small communities have sprung up, and small businesses have developed.
This all puts a heavier burden on the Canal especially since most of the private houses and businesses have their own septic systems, some of them many years old and poorly maintained. Undoubtedly many of these estimated 5500 septic systems are contributing their share of nitrogenous wastes to the waters of the Canal. Other sources of effluents are heavily fertilized lawns and gardens, animals wastes, and wastes from small businesses.
The result of all this is that dead zones, which were initially only occasional, autumnal occurrences in the southern part of the Canal around the Great Bend region, have now spread to a much larger area and persist for much of year. This is most noticeable in the deeper parts of the canal but now has been observed at shallower levels also.
Fish need between 5 and 20 parts per million (ppm) (the same thing as mg. per liter) of dissolved oxygen to survive and thrive. Below 5 ppm they are stressed and below 3 ppm they die. But recently, for a stretch of the canal extending from Hamma Hamma to Belfair at the south end of the canal, the levels have measured below 2 ppm for much of the year. Usually the dissolved oxygen (DO) problem is worse at depths of 30 feet or lower but even surface waters have been affected so that there is no place where the fish can escape. Not only fish have been adversely affected by this situation but also shrimp, crabs, octopuses, and other invertebrates.
Well now, what should we do about it? The solution to the problem seems pretty straightforward but for the contrary nature of humans. Thus, according to a 1986 report of Puget Sound Water Quality Authority, Hood Canal does not offer sufficient area for properly operating septic systems because houses are located on small lots on the shoreline. They also linked septic system problems to closure of shellfish beds. But here we are, still studying the problem while the population keeps growing.
But something is being done. On October 14 of this year the Puget Sound Action Committee announced $790,000 in awards to various organizations to help solve the problem. I will mention just a few of them here to give you an idea of what's going on. The Skokomish Tribal Nation is receiving $92,000 to research what to do with the chum salmon carcasses remaining after they have been stripped of eggs. In the past they were simply thrown back into the canal to rot. The Hood Canal Coordinating Council will receive $160,000 to assess new septic system technologies and educate shoreline residents about them. Other grants are going to organizations to study new ways to treat livestock wastes, to educate homeowners about ways to keep fertilizer and pesticides out of the canal, to perform shoreline surveys, and collect water samples to check for pollution, etc. But, so far as I know no new laws or regulations to limit pollution have been passed. The complete list of these grants can be found at www.psat.wa.gov/News/releases/new_04_10.htm.
In closing, I must admit that collecting information for this article and writing it was pretty much like Yogi Berra's "déjà vu, all over again". I wonder if we can ever learn from other people's experiences or must we repeat their mistakes over and over again to the last syllable of recorded time?
References:
Puget Sound Action Committee (PSAT): www.psat.wa.gov/News/releases/news04_14_10.htm
PSAT: www.psat.wa.gov/Programs/hood_canal/hc_what_you_do.htm
PSAT: www.wa.gov/Publications/PACA_html/paca_intro.htm
The Olympian: www.Theolympian.com/home/news/20031015/southsound/124520.shtml
Hood Canal Dissolved Oxygen Program: www.prism.washington.edu/hcdop/dataobservaions/s_hc_pg2.html
USGS: wa.water.usgs.gov/projects/hoodcanal/publications.htm
Cyber Diver Network: www.ednn.info/eco/ee040506/e40506.ml