Green Water in Silver Bay

Recently the water in Silver Bay has been exceptionally green, almost like it was seeing glacial run-off. I recall this happening last year as well, and at the time I noticed it I wondered if maybe it was dust from all the blasting and rock work being done on Sawmill Creek Road and for the Blue Lake dam project. When talking to some others about it, I was told about coccolithophores, a single-celled (mostly marine) algae that can turn waters blue-green color when they are abundant. Giving the seasonal timing of the color change along with the fact that rock work is greatly diminished this year (the road is done, and the dam is getting closer), it seems far more likely an explanation than rock dust from blasting. That said, it does raise some other questions for me.

In any event it’s a good time, especially with these sunny days, to get out and enjoy the newly completed road and separated bicycle/pedestrian path with normally amazing view now intensified by the colorful waters.


  • Does anyone else remember noticing this happen before last year (I don’t)?
  • If it did not happen in prior years, what has changed? (Last year was exceptionally sunny during the summer, but this year has been quite rainy.)
  • Why does the bloom seem mostly limited to Silver Bay and nearby locations where the blue-green likely originated in Silver Bay?
  • Are there other places in the broader Sitka area where this is occurring?

5 thoughts on “Green Water in Silver Bay”

  1. Interesting, seems as though the coccolithophores are a carbon sink. This could be another sign of climate change. Last year was my first year noticing it in Sitka as well. Yes they are all over Sitka sound.

  2. Hi Matt,

    Thanks for the link to the coccolithophores. Great pictures.

    I live in Thimbleberry Bay, pretty close to Silver Bay, and we’ve been noticing this for about a month. I don’t recall ever seeing it before in the 14 years we’ve been here.

    For what it’s worth, I saw the same greenish color last week returning from a trolling trip south of town about 25 miles, in Cameron Pass and fading out around Dorothy Narrows.

    The bloom has brought in some small “feed” fish. Possibly perch, and salmon fry. We saw murrelets a couple days ago close to shore, and I don’t ever remember seeing them this close. A number of gulls too, including mew gulls (if my poor identification is right) that we normally don’t see this time of year.

    Interesting stuff!

  3. Thanks for the comments Dan and Zach – it’s sounding like this algae bloom is a pretty recent development. I spoke with Ritch Phillips who has worked out at Medvejie Hatchery for many years, and he also said last year was the first he had ever seen it. It will be interesting to see if it’s just a one or two year thing, or if it continues to be a seasonal occurrence. I wonder if anyone is looking into the reasons for these blooms and the possible effects they are having.

    Zach – interesting about the small fish and the Marbled Murrelets. I just got an e-mail from someone who had the impression that there have been more murrelets out in the sound this year and he was wondering if others had mentioned it. I also have seen murrelets very close to shore (at Magic Island – so close even that a person fishing for rockfish from shore accidentally caught one; fortunately it seemed fine when it was unhooked), though since I don’t spend much time out there, I didn’t know whether that was unusual.

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