Trouble Call Program

Water Quality Alert:

Noctiluca

On the evening of June 2, 2005 the King County Office of Emergency Management was notified of an unidentified "red-sheen" near Point Wells in Puget Sound.  Staff from King County's Environmental Lab responded to the field and initially visited the Richmond Beach area.  Staff didn't observe any substance at this location so they moved south and other beaches were checked.  At 2030 hours, they observed what appeared to be Noctiluca along the shoreline of Carkeek Park in Seattle.  Some of the Noctiluca was moving onshore so a sample was collected.  The next morning, microbiologists from the lab analyzed the sample and the substance was positively identified as Noctiluca.

Noctiluca is a large dinoflagellate that is named for its ability to bioluminesce--or glow--at night.  During the day, large accumulations of this organism appear to be orange-red to rust brown and it looks like tomato soup. Although this is a red tide forming organism, Noctiluca is harmless and non-toxic.

For a number of weeks in May and June, Noctiluca is often observed in the marine waters of the Puget Sound region.  Among more common sightings, it can usually be seen along the shoreline of West Seattle and Vashon/Maury Island.  This year, we also had reports of Noctiluca near Three Tree Point in Burien and Holmes Harbor on Whidbey Island.

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