Cyanobacteria & Dinoflagellates: Toxins From Water and Algal Blooms

What cyanobacteria and dinoflagellates are

Cyanobacteria (blue-green algae) and dinoflagellates are microscopic organisms that live in fresh and marine water. Under the right conditions — warm temperatures, stagnant water, excess nutrients — they multiply rapidly into harmful algal blooms. Many species produce potent toxins that can harm people, pets, and wildlife.

Exposure usually happens through:

• Drinking or swimming in contaminated water
• Inhaling aerosols near a bloom
• Eating fish or shellfish that have accumulated the toxins

How it can affect you

Cyanotoxins and related algal toxins can affect the liver, skin, gut, and — importantly — the nervous system. Neurologic symptoms may include:

• Headaches and dizziness
• Numbness or tingling
• Muscle weakness
• Visual disturbances
• Fatigue and brain fog

Some of these toxins are true neurotoxins, meaning they directly interfere with nerve function. Because the retina's rod cells are highly sensitive to neurotoxic effects, a contrast deficit can appear even when other symptoms are mild.

How VCS screening helps

A VCS screen measures contrast sensitivity across five spatial frequencies. Neurotoxic effects from algal toxins tend to reduce sensitivity in the fine-detail frequencies — the pattern the test is designed to detect. If you've had known or suspected exposure to a harmful algal bloom, a VCS screen can help flag whether your nervous system shows a measurable effect.

What to do next

1. Avoid exposure — stay out of water with visible blooms and follow local advisories.
2. Screen yourself — take a free VCS test to check for a deficit.
3. See a provider if symptomatic — particularly one familiar with environmental or biotoxin illness.
4. Re-screen over time — to see whether function normalizes as exposure resolves.

FAQ

Can I be exposed from drinking water? Yes. Some cyanotoxins are not removed by standard water treatment. If your source water is near a bloom, consider testing and alternative water.

Is a VCS result specific to algal toxin exposure? No. The screen is non-specific — it flags a possible neurologic process, not a particular toxin. It's most useful alongside your exposure history.