Marine algae & plankton

Sometimes algae blooms look like spilled paint, oil, or sewage. Sometimes spilled contaminants can look like a bloom. Call if you are unsure.

Report an Environmental Issue tells what to do if you suspect that you are seeing pollution.

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).

The Shellfish Safety Information map at the Washington State Department of Health can tell the status of shellfish harvests in Washington.

Phytoplankton blooms are a natural occurrence in the spring. Blooms can also occur in summer and fall when there is an increase in nutrients from natural sources, such as wind-driven mixing of surface waters with deeper waters, or human sources, such as wastewater treatment plants. As phytoplankton use up the nutrients in the surface waters, their growth slows and cells eventually die.

Dying blooms can be an environmental concern because the cells sink and decay. Bacteria decompose the organic material, stripping oxygen from the water. This microbial oxygen demand, at times, leads to very low oxygen conditions in the bottom waters, possibly harming aquatic life.

We are taking steps in Puget Sound to determine how human activities and natural factors affect nutrient and low dissolved oxygen levels.