SEEN OFF WEST SEATTLE: Almost-annual algae bloom, resembling but NOT a spill

Thanks to Chris Frankovich for the photo from The Arroyos, where what is almost certainly the almost-annual algae bloom has shown up. We’ve reported on similar sights most years since the early 2010s; it’s usually a type of algae known as Noctiluca. Experts say it’s not usually toxic – this isn’t what is meant by “red tide” – but can be irritating; it’s a sign of environmental imbalance, including too many “nutrients” in the water. Here’s more info from state scientists. Here’s a sampling of our past reports – from 2011, 2023, and 2024.

1 Reply to "SEEN OFF WEST SEATTLE: Almost-annual algae bloom, resembling but NOT a spill"

  • Erwin June 27, 2026 (9:30 pm)

    Thank you for this post and for such a clear photo.  Today, 6/28/26 I found a similar copper color “spill” north of Salty’s, south-east of Alki.  It disturbed and worried me.  At least now I know what it is.Thank you

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