A Shallow Water Dead Zone In Puget Sound

10 Nov, 2014

By Ron Shimek with illustrations by Jan Kocian


Over the past many years when I have spoken to many aquarists, students, and other audiences about modern and ancient biology, one of the implicit themes for my discussions has been the ubiquity of death as a biological factor.  This may seem odd, for after all, the word “Biology” is defined as the study of life.  Nevertheless, it has many times been noted that “death” is the price we pay for being alive.  Death is the reason for evolution, the less-fit die… leaving those animals that are more fit.

The ways in which organisms perish may run the gamut from the singular, everyday, ultra-mundane and almost meaningless death – meaningless except, of course, to the creature involved, which leaves the world much as it was before; to being a minor part of a huge array of dying, referred to as “a mass extinction event” that may radically change the world’s remaining array of living creatures.

In our explorations of the natural world, we often see – and often are the cause – of the timely or untimely end of some creatures.  Sometimes these events are welcome, such as the delightful revenge swat terminating the existence of a female mosquito while she is trying to procure a blood meal for the development of her eggs.  More often, the events are essentially inconsequential; such as the perishing of innumerable members of the aerial insect plankton as they impact with the teeth of innumerable smiling, speeding motorcyclists.   And some deaths are apparently meaningless, and perhaps all the more tragic for that, as the many organisms that perish over a large area for no apparent reason other than bad luck, when nature serves up a plate of natural disaster, such as the unimaginably humongous volcanic eruptions of the Siberian traps of about 251 mllion years ago; eruptions that nearly brought multicellular life to an end, or the somewhat lesser, but much faster, and probably much more visually exciting, cosmic Croquet crash of 65 million years ago that left only the birds as living dinosaurs.

At the other end of the scale are the more local extinctions that impact every ecosystem now and then, or periodically.  Such local extinctions range from the drying up of a mud puddle, which may have thriving populations of many microbes, to the death and destruction wrought upon many suburban monocultural grassy meadows when they are mowed weekly in the summer, to the massive death and destruction in the clear cutting of a forest, finally to those much more serious events in marine ecosystems referred to as “Dead Zones”.

Dead zones are just what the name implies, areas where life is lacking, either permanently or on some sort of transitory scale.   The largest dead zones are in enclosed oceanic basins where the bottom is permanently anoxic and the waters are full of sulfides.  Given the name of “Euxenic zones” because the largest such is found in the bottom of the basin containing the Euxenic ( = Black) Sea, these areas are totally devoid of aerobic life, although they generally have thriving communities of anoxic bacteria and archaea.  Euxenic zones are generally permanent.  However, there are many types of transient dead zones.

Short-Term Marine Dead Zones

Some of the more “classic” of marine dead zones were characteristically of short duration and caused by the superimposition of several physical events coupled with some unfortunate biological events.

Commonly referred to as “red tides”, these events occur regularly along many shorelines, and although the resulting mortality events tend to look the same from above the water’s surface, the causes are often different from place-to-place and are quite often difficult to determine.  In the dim, dark, ancient days of legend and mythos when I was but a mere studentling, I took a class from an esteemed, exalted and venerated professor of classical rank whose words, like those of the acclaimed Aristotle in the not too distant past, were absolutely unquestioned.   Although his reputation has faded somewhat as times have passed, many of his studies remain classics from the founding days of population ecology.  About the time of my birth, he was one of the first researchers to hypothesize a cause for red tides that appeared to be reasonable and met the test of experimental validation.

However, almost 20 years later, while taking a course at the Marine Biological Laboratory in Woods Hole, Massachusetts, I listened to him characterize his search for the cause of red tides in Florida, as a search looking for some event or factor that wasn’t there, which he realized should be easy to find as it wasn’t there in large quantities.  So all one had to do to find the cause of these red tides was to evaluate the ecosystem in question and then find was what was missing in the largest quantities from that ecosystem.  That, in turn, would lead you to the yellow brick road, and eventually to the answer you were seeking (Slobodkin, 1953).  As an aside, this fellow’s lectures were all suffused with similar logic.  It made taking notes and subsequently rereading those notes to try to understand what had been said in the lecture a real joy, and we students were universally glad that this class was graded on a simple credit/no credit system.   Basically, if you showed up for the class, you got credit.  Ah… Sigh….

Red tides may or may not have a primary human cause or may simply, and misleadingly, appear to have such a cause.   When a dead zone appears in close proximity to a metropolitan area, or a source of agricultural runoff, probably the first cause of the event is considered to be some sort of pollution; and this is justifiably so.  However, in all such cases, the actual cause of the event needs to be examined much as a forensic examination needs to be done in the case of a criminal investigation.   And just as the forensic examinations portrayed in television “dramas” are only tangent to reality, the biological forensic examinations of a marine “event” are very different than what is thought to occur by even the well-educated public.  Probably the biggest difference is the speed by which things don’t occur.  Many of the necessary examinations require a great deal of time and painstakingly detailed work to reach a result.  For even a small and simple event, it may take from weeks to months to analyze samples and get definitive results.  Nevertheless, the process is an interesting and quite amazing one.

Right NOW!!!

Presently, several different investigations of biological problems are being investigated in virtually every major estuary in the United States, including the Puget Sound of the Pacific Northwest.   These include, in no particular order, studies of changes occurring due to global climate change; studies investigating the effects of introduced species, particularly with regard to their effects on native species that are important in commercial and sports fisheries; studies examining the natural history of ecologically important species, such as, in Puget Sound, all the species of salmon, as well as other fishes and various crustaceans such as Dungeness crabs, and important mollusks such as geoducs, and of course, marine mammals such as killer whales, and sea lions.  Also, there is an emergency study or series of studies trying to get some sort of handle on the immense mortality that is presently being seen in many sea star species along the entire West coast of the U. S. and Canada.

Jan Kocian, diving photographer extraordinare, and my co-author for this blog, has been actively surveying several marine subtidal areas in northern Puget Sound for some time, with the objective of obtaining photographic evidence of, particularly, the sea-star wasting disease epidemic.  As is often the case in a study such as this, serendipity will rear its head, and wholly unexpected observations will be made.

Figure 1.  The habitat in a typical, “healthy” and normal view is shown at the bottom.  The dying or dead brittle stars are coming out of the habitat, probably to avoid the anoxia that occurred in the sediments.

Figure 1.  The habitat in a typical, “healthy” and normal view is shown at the bottom.  The dying or dead brittle stars are coming out of the habitat, probably to avoid the anoxia that occurred in the sediments.

On 18 September, 2014, Jan had just finished his weekly survey dive at the wharf at Coupeville on Whidbey Island, Washington.  He reported that “The many mottled sea stars (Evasterias trochellii) which until recently escaped the wasting disease now were now gone, having died off, and those few survivors didn’t look all that healthy, either”.  Leaving his normal survey area near the pier, looking for better water clarity, he started seeing things he had never previously observed.  At depths from about 7.5 m  to 9 m ( about 25 feet to about 30 feet), there were many animals lying exposed on the sandy sea floor, looking limp, sick or dead.  Red sea cucumbers (Cucumaria minata) were flaccid and dead, while several Aleutian Moon snails (Cryptonatica aleutica) were in odd postures.  Proceeding a bit further, brittle stars, which had always been buried deep in the sediments showing only their arms waving in the light current, had crawled out of the sediments and were lying wholly exposed all over the surface of the muck, showing their entire bodies.  A few were even uplifted as if they were starting to spawn.  In the midst of the stars were some pink/yellow worms, another rare or unusual sight.  These worms were Polycirrids, a group recently split off from the Terebellids.  Also dozens and dozens of Nuttall’s cockles (Clinocardium nuttallii) were on the sediment surface with their siphons out, instead of being buried as they normally are.  

Stressed Cockles

Figure 2. Stressed or dying cockles. The black layer seen on some of the cockles indicates that their normal habitat is aerobic only near the surface, and anaerobic deeper in the sediment. It is likely that the anaerobic conditions became more pronounced and caused this dying zone.

Dying Green Urchins and Brittle Stars

Figure 3. Death of the sea urchins and brittle stars.

Dead and dying sea cucumber

Figure 4. Cucumaria miniata dying and decomposing.

Everything's dying.

Figure 5. Dead, dead, dead, and dead – or dying

Returning to the site two days later, on the 20th of September, to survey the site and to do some wide angle photography he found the impacted area was now covered with a layer of cloudy or milky water.  Water clarity was reduced to only a few feet which rendered wide angle photography difficult.  After examining the site, with regard to the extent of the dead zone, it appeared that depth didn’t seem to be a critical factor, at least on the shallow side of the site and topography didn’t seem to have enough differences to cause the changes, either.

On a return to the site on 22nd September, the area containing dying animals was not only still present it was spreading; whatever seemed to be the cause was still doing its dirty work.  Documenting the milky water was difficult, as the layer was not particularly well defined, nevertheless, there was a lot of flocculent material floating in it.  The sites he had previously photographed were now wholly within “the Milky Way” which made photography difficult.  However, outside the cloudy water, the many tube dwelling worms in the area’s sediments were apparently unaffected.   The milky water appeared to be created from within the sediments.  The water was not cloudy like this when he first found all the infaunal creatures on the surface.

Milky Water Layer

Figure 6. Milky water layer with flocculent material, probably due to decomposition byproducts.

Black sulfide bacteria on surface

Figure 7. The white and black condition of the sand is due to the decomposition of all the infaunal animals that came up from the sediments and died on the sediment surface. The white is a characteristic bacterial genus named Beggiatoa. It has several species that metabolize hydrogen sulfide and decomposing critters.

Bacterial Mat

Figure 8. The aftermath. Sulfur bacterial mats formed by metabolizing decomposing animals in the sediment.

Three days after this, on 25th September, upon returning to the site, conditions had changed considerably.  The milky water layer was gone, although there still was flocculent material in the water.  Strong winds in the previous couple of days appear to have blown the milky, possibly stagnant, water mass away or mixed it with cleaner offshore water.  The brittle stars on the surface were gone, possibly blown away in currents,  although there were some arms waving above the sediments, indicative of a few stars still living below the surface.  Whether these were the same stars that had been on the surface or others that had remained below the surface is unknown.  The clams were not visible on the surface, but the horse clam siphons were visible in their normal postures.  Most other animals, such as the worms, were no longer visible on the surface.  The exceptions were the red sea cucumbers, Cucumeria miniata, where many specimens were lying fully exposed, and apparently dead, on the surface.  As their tissues contain a lot of toxic saponins, scavengers tend to leave these dead Cucumaria miniata alone.  It may take several weeks for their bodies to slowly decompose.

Jan continued his regular dives on the 29th of September.  While visibility in shallow water was still good, upon entering the area of the dead zone, the visibility was much worse than in the surrounding area, but the water was not milky.  A few living Cucumaria were acting oddly, not quite dead, but just slightly responsive to touch.  The horse clams buried in the sediment were extending their siphons and apparently feeding.  These could have been clams that had not extended their siphons through the event and finally tried feeding again, or they could have been clams that had been on the surface and subsequently reburied.  Some more brittle stars were found on the surface, many with autotomized arms.  Numerous green sea urchins were found with their spines in abnormal postures, definitely not looking healthy.

At this time, Jan was not looking too healthy either, having caught a cold.  He was unable to return to diving until the 12th of October.  When he could return to the site, in shallow water, it appeared that all was back to normal, the Cucumaria miniata was feeding as usual and the brittle stars were extending their arms from the sediments apparently feeding normally.  However, the water clarity was poor; only about 1.1m to 1.5m (four to five feet).


Decomposing Red Cucumber

Figure 9. The white bacteria are about the only thing that will decompose the sea cucumbers, because of the toxic chemicals in their body walls.

Dropping down to 40 feet (12 m) the seabed was black instead of its usual grey-brown, and it was covered with a white bacterial mat.  This white mat is often referred to as Beggioatoa, which is a bacterial genus that is found in hydrogen sulfide rich environments.  It is a typical pollution marker for areas that have been rendered anoxic, killing much of the infauna.  Typically in areas such as these, the environment will be aerobic during the day, due to algal photosynthesis, but because of the amount of organic matter in sediments, once the sun goes down, so does the oxygen concentration and the sediments become anaerobic or anoxic.

Over the next week, on dives until the 19th of October, the dead zone appeared to be evident.  The full extent of the dead area, and the reason for the mortality, remain indeterminate.  Typically in Puget Sound, the benthos is very rich, so that a mortality event such as this may take several months for even partial recovery.  Although the substrate will appear to recover in a few months, quantitative sampling will show the benthos make take two or more years before it has returned to normal.


de Matos Nogueira, J. M., Fitzhugh, K., & Hutchings, P. 2013. The continuing challenge of phylogenetic relationships in Terebelliformia (Annelida: Polychaeta). Invertebrate Systematics, 27(2), 186-238.

Long, E. R., Dutch, M., Aasen, S., Welch, K., & Hameedi, M. J. (2005). Spatial extent of degraded sediment quality in Puget Sound (Washington State, USA) based upon measures of the sediment quality triad. Environmental monitoring and assessment111(1-3), 173-222.

Shimek, R. L. 1992. North Beach High Intertidal Biota in the Area of Proposed Beach Modifications: Sediment Infauna and Beach-Wrack or Drift Biota. Pages 1-67. Parametrix, Inc., Seattle. Shimek, R. L., T. Thompson, and D. Weitkamp.  1991. Slag, benthos, and bioassays: poor correlation of bioassay predictions and the benthos. In:  Chapman, P., F. Bishay, E. Power, K. Hall, L. Harding, D. McLeay, M. Nassichuk and W. Knapp (Eds.)  Proceedings of the seventeenth annual aquatic toxicity workshop, November 5-7, 1990, Vancouver, B. C.  Canadian Technical Report of Fisheries and Aquatic Sciences. No. 1774. Vol. 2:1046.

Shimek, R. L., T. A. Thompson, T. H. Schadt, and D. E. Weitkamp.  1992.  Interpreting conflicting biological and chemical results from a Puget Sound sediment data set.  Puget Sound Water Quality Authority. Puget Sound Research ’91, Proceedings. 2:546-552.

Slobodkin, L. B. 1953.  A possible initial condition for red tides on the coast of Florida. Journal of Marine Research, 12(1): 148-155.

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About the author

Avatar photo
Ronald L. Shimek, PhD

I am a marine biologist/invertebrate zoologist who got captivated by - or sucked into - the reef aquarium hobby late in the last millennium, I have written widely in the hobby press and elsewhere, mostly about invertebrates (in the context of the hobby, anything but fishes) and how to keep them alive. I reside in Wilsall, Montana, about as far from the ocean as one can get and still live in the contiguous 48 states, go figure... What can I say, it is home. :-)


  1. November 18, 2014

    Well documented set of observations, thank you.
    Stirs up hypotheses…
    Now I’m wondering whether that area received bunker oil from that recent derelict ship sinking in Penn Cove? I imagine a slug of oil in sediment might’ve shifted following storm and initiated a die-off by changing the microbiome.

    I look forward to future posts.
    (I am an Interpretation volunteer at Seattle Aquarium, and sometimes get questions about the ongoing echinoderm syndrome.)

  2. November 18, 2014


  3. joe
    November 18, 2014

    Thank You for the well documented presentation. Credible investigation is sorely needed. I hope that along with virology and bacteriological studies there are full radiological tests. I remember Philippe Cousteau saying he believed that the ocean was at a tipping point during the BP blowout in the Gulf of Mexico. Between Climate, tsunami debris, nuclear release and it’s condition prior to 3/11/11, Maybe we pushed it over the edge and it truly is dying.

  4. joe
    November 18, 2014

    …Fro what it’s worth – this got me teared up. Sad does not even begin to describe it. Thanks.

  5. November 18, 2014

    Did you ever consider the cause to be Fukushima? You idiot.

  6. November 19, 2014

    It cant be Fukushima, it must be a bacteria or virus. There are only 2 bequerels of cesium per liter of water as tested on the Central California coast. That is less radiation than a Japanese banana eating contest. If you think the entire ocean is contaminated with numerous known and unknown radio nuclides that are ionizing h2o and creating a unprecedented amount of free radicals in the ocean and adjacent atmosphere, you are crazy. If you think that 3 massive nuclear reactor cores, that exploded, creating unimaginable amounts of fallout into the pacific ocean and melted down into the basements of their containment buildings where 400 tonnes of water rushes around the totally new type of radioactive metal blob that is water soluble and seated on the edge of the Pacific ocean has any impact on marine life, your delusional. get real. That kind of stuff only affects the environmental activists and conspiracy theorists. Now get back to work and pay your taxes, Obama care is about to be over run with thyroid cancer, childhood leukemia, neural tube defect babies and cardiac related health epidemics, due to some totally unrelated mysterious bacteria or virus that can not be identified or explained but must be the culprit, because radioisotopes don’t hurt people, just ask Marie Currie. God Bless, it is all in the book of Revelation, try reading it some time, its relevancy will blow your mind. “power of the stars”, “vile judgments”, “angel cast a star into the sea and made the water bitter, 1/3 of the ocean dies”

    • Edu
      November 22, 2014
    • December 05, 2014

      “It can’t be Fukushima” because there are only so and so beckerels of cesium THATS FUNNY are you able to track the many THOUSANDS of MOX isotopes that are spewing into the Pacific every day from Fukushima which is a never ending nightmare!? More than 300 tons of it EVERY DAY! Where do you think that is ending up, in OZ? Please. OPEN YOUR EYES.

  7. November 19, 2014

    Dana Durnford says hi.

  8. November 19, 2014

    No Thing to worry about. You were witness of a Evolutionairy Happening and 40.000 New Species Will Come from it You ´ll See.

  9. November 19, 2014

    Thanks for this research on the state of the Puget Sound, but ignoring the cumulative impact of the poisons legally sprayed into the Puget Sound to “eradicate” pests to shellfish aquaculture such as eelgrass, which is essential to the marine food chain and ecosystem, is to ignore a significant source of threat.

  10. November 19, 2014

    Of course it’s not Fukushima but those who say it is are connecting their Dots and have been listening/watching poor information. Yes there are on-going Atmospheric releases in order of 70 Million Becquerels every hour and 400 Tons of Highly radioactive water dumped into the PAcific daily but still we have no reports of Highly radioactive fish caught on the West Coast as we have on several occasions in Japan, and each time with higher levels than previous fish caught, but No stories of Marine life die-offs in Japan. Not a single story from fishermen mentioning how the fish are all dead off Japan’s Northern coast but we have people here in North America thinking somehow are West Coast Marine life is dying because of Fukushima radiation. Amazing how these people can jump to such conclusion with such little information or understanding of radiation.

    Had it been a Radiation plume from Fukushima then I’d suspect that since the radiation levels within that plume are so high to cause such devastation here in Puget sound the surely it’s killed many more places along it’s journey and indeed must still be out there killing to day seeing that traveling across the entire Pacific didn’t dilute it then surely another trip around Puget sound won;t either.

    Common sense is rare nowadays…too bad or else they’d all know Co2 is great for mother Earth, her plants thrive on it and since Co2 levels are at their lowest in 460 Millions years then it only make sense why the Earth had more Vegetation when Dinosaurs roamed as levels were much higher than today.

    have a nice day

  11. November 25, 2014

    Thank you for this presentation of a dead zone. It may have resolved a mystery that has been bothering me.

    I am an amateur naturalist, interested mainly in the intertidal fauna of Boundary Bay. I maintain an aquarium with some of the smaller animals from the west side of the Bay.

    I have observed a couple of die-offs, one lasting several years, below the cliffs on the west end of White Rock which I attributed to the heavy construction projects on the top of the cliff. For a few years, I was using water from the Bay for my aquarium, which introduced many interesting organisms to the tank, but also caused two tank failures. Now I’m using commercial “Instant Ocean” and filtered water. Vegetation is replenished periodically from the southwest end of the Bay.

    However, even using commercial water, and with an apparently healthy tank, I found a white mat growing on leftover tank sediments after a scrub at the end of September. It looks like the mat you have documented here, the Beggiatoa.

    I posted photos on my blog, here: http://wanderinweeta.blogspot.ca/2014/09/no-end-to-mysteries.html . Would this be the same organism?

    I recently brought home three mottled sea stars, very small ones that came along with seaweeds cast up on the shore after a storm. They look healthy.

  12. November 29, 2014

    I have borrowed an image from this article for a blog post about Beggiatoa. I think this conforms to your copyright conditions, as it is used on an educational and non-commercial blog. I have included links to this article in the previous blog post, (http://wanderinweeta.blogspot.ca/2014/11/underwater-epidemic.html), and will in the current article, as well. If there is a problem, please notify me and I will remove it immediately.

    Thank you!

  13. August 14, 2015

    The start of the oceanic food chain begins with those barely visible little creatures they call phytoplankton.Seven twelfes or thereabouts of planet Earths surface area which is exposed to the sun on a once daily bas been responsable for the proliferation of what we regard as life.Those wee small creatures that are virtually invisible to the human eye actually clean up most of the shit we leave ,provide us with the oxygen we breath,etc, etc.Once the phytoplankton become upset dats dat.

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