Blue-Green Algae and Harmful Algal Blooms
Blue-green algae are not algae at all but are photosynthetic bacteria, also known as cyanobacteria. There are several species of blue-green algae, which thrive under their own unique conditions and produce a variety of toxins. Blue-green algae are naturally occurring and usually present in a water body, but they typically exist in numbers too small to cause problems. Blue-green algae growth is influenced by a variety of environmental conditions including temperature, flow, nutrient levels, light, weather, vertical mixing in the water column, and pH levels.
Given the right conditions, high concentrations of blue-green algae can occur and form a bloom. Blooms can vary in appearance, sometimes looking like mats, foam, or surface scum. Blooms can range in color from blue and bright green to brown and red. Some blooms produce a foul odor. Not all blooms are toxic, but when toxic harmful algal blooms do occur they present a health risk to humans, pets, and livestock. Exposure may occur from ingestion, skin contact, or inhalation. Exposure can result in a range of health effects from skin irritation and stomach upset to neurotoxic effects and at very high levels, death. Symptoms in humans are rare; anyone with symptoms should seek medical attention.
If you observe a blue-green algae bloom, contact your DEQ regional office.
Blue-Green Algae Health Advisories
Health advisories are typically issued by the public health districts, who work closely with DEQ staff.
Take the following precautions when an advisory is in effect:
- Avoid exposure to water experiencing a harmful algal bloom. Take extra precautions to ensure children, pets, and livestock are not exposed to the water.
- Do not consume water with a blue-green algae bloom. Neither boiling nor disinfecting removes blue-green algae toxins from water.
- If fish are known to have been exposed to a blue-green algae bloom, only consume the fillet portion (remove the fat, organs, and skin). Wash hands after handling. The risk associated with consuming fish caught in waters with a blue-green algae bloom is unknown. Toxins produced by blue-green algae can accumulate in the organs of fish.