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Harmless Red Algae Bloom in Puget Sound

by Kurt Hoehne

Last night off Shilshole Bay Marina I sailed through some of these blooms. Pretty dramatic, but as it turns out pretty harmless. Here’s the lowdown from the Washington Department of Ecology –KH

OLYMPIA – The Washington Department of Ecology has received laboratory confirmations that several red-orange algae blooms showing up in Puget Sound are harmless to people.


See photos of some of the blooms online.


The blooms are not the so-called “red tide” that refers to paralytic shellfish poisoning.


According to Dr. Christopher Krembs, senior oceanographer with Ecology’s marine monitoring program, reports of the algae bloom sightings are coming to Ecology from:

Photo courtesy of Department of Ecology.

Photo courtesy of Department of Ecology.


  • Alki Beach
  • Bainbridge Island
  • Boston Harbor
  • Des Moines
  • Edmonds
  • Elliott Bay
  • Shoreline
  • Sinclair Inlet
  • Strait of Juan de Fuca


The harmless red-orange bloom is Noctiluca (pronounced “nock-ti-LU-kah”), a harmless single-celled micro-organism that occurs normally this time of year. This type of plankton does not photosynthesize but gets its red color from the phytoplankton it eats.


Krembs said: “This type of bloom shows up as large, red-brown, even orange ‘tomato-soup-like’ streaks along current and tidal convergence lines.”


The blooms tend to accumulate along shores and beaches. As the sun warms the water, the water stratifies, holding the tiny plankton near the surface where they flourish.


“Citizens have sent us multiple images taken from shore,” Krembs said. “This is a testament to the value of citizen observations. We can’t wait to get an Eyes Over Puget Sound flight next week to check this out. I am very interested in seeing the entire scale of it.


“We are seeing these blooms arrive three weeks earlier than the last two years. This comes following a change back to expected oceanographic conditions from the previous two years that were colder and fresher,” he said. “With the weather being this mild it is not all too surprising to have blooms starting in May.”


Ecology often receives inquiries from the public who suspect an oil or paint spill.


If you see red, brown or orange colored water in Puget Sound, it is likely this bloom. However, Ecology continues to encourage the public to report any suspected pollution in the water.


If you are observing an algae bloom in freshwater, be extremely careful. It could be a toxic algae bloom that is poisonous to people and pets.


You can report pollution problems to the Department of Ecology online or by calling the Ecology office nearest you as listed here.


For more information:


Learn more about marine and freshwater algae blooms.

Ecology Marine Monitoring Program

Ecology’s website

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