Harmful algal blooms can: Produce extremely dangerous toxins that can sicken or kill people and animals. Create dead zones in the water.

Is green algae harmful to humans?

Some blue-green algae can produce toxins, some do not. ... Exposure to high levels of blue-green algae and their toxins can cause diarrhea, nausea or vomiting; skin, eye or throat irritation; and allergic reactions or breathing difficulties.

Can algae kill humans?

Toxic algae can be fatal if a person drinks water from a bloom that contains certain toxins. In California, the most alarming toxin is domoic acid, which can disrupt normal nerve signaling in the brain, causing disorientation and seizures. It can cause death to fish, seabirds, marine mammals and even people.