What Is That Red Streak in the Water off of Bainbridge Island?

In late summer to early fall, you can see a red streak in the waters of Bainbridge Island.

This is the annual zooplankton bloom of the dinoflagellate algae, often referred to as “red tide.”

The bloom is caused by a surplus of nutrients. The population of the dinoflagellate algae can jump to more than 20 million per liter along some coasts, causing the water to turn red.

According to the Washington State Department of Ecology, “most blooms are harmless, but some types of blooms can produce toxins that can make people sick if they are exposed to high enough levels of the toxins. Exposure can come from inhaling or swallowing water with toxins or from eating contaminated shellfish (that fed on the toxic phytoplankton).”

Red Streak in Manzanita Bay, Bainbridge Island

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