Harmful Algal Blooms

Sick dogs, scummy water, and distressing media stories. Algal blooms are becoming more common in the Columbia River.

This FAQ explains harmful algae blooms, how they impact the Columbia and human health, and what we can do about them. Let’s dig in.

What are harmful algal blooms?

Algae are simple, photosynthetic plants that play an important role in the food web in freshwater systems. Algal blooms are overgrowths of algae or algae-like bacteria in the water. They can be green, red, pink, blue, or brown and can be scummy or slick “spilled paint” looking and may or may not produce a musty, foul, or “rotten-egg” smell. Harmful algal blooms (HABs) are algal blooms that produce dangerous toxins. Not all algal blooms are toxic, but even non-toxic blooms can be problematic. HABs can occur in freshwater, brackish, and saltwater. You may have heard of HABs called red tides, blue-green algae, or cyanobacteria.

What are cyanobacteria?

Also called blue-green algae, cyanobacteria are true bacteria, but have chlorophyll-a like algae. Functionally they act like algae, which is why they are typically considered part of the algal community. Cyanobacteria are the most common culprit of HABs in freshwater in the United States. They thrive in warm, slow-moving, nutrient-rich water (specifically nitrogen and phosphorus). 

illustration of people at the beach where algal blooms are occurring

What are Harmful Algal Blooms?

Algal blooms are overgrowths of algae or algae-like bacteria.

Harmful algal blooms (HABs) are algal blooms that produce dangerous toxins that can make people and pets sick. Cyanobacteria are the most common culprit of HABs in freshwater in the United States. They thrive in warm, slow-moving, nutrient-rich water.

What are the risks?

HABs can produce extremely dangerous toxins that can sicken or even kill people and animals. These blooms can severely impact human health, ecosystems, and the economy. The most common health effects come from drinking contaminated water or ingesting it while swimming or recreating. HABs can also cause problems for drinking water treatment systems. Pets are particularly susceptible to toxic algae because of their relatively small size and likelihood of drinking contaminated water.

Why are harmful algal blooms happening on the Columbia?

Worldwide the frequency and duration of toxic blooms have increased in recent years. Since toxic algae love warm, nutrient-rich, slow-moving water, we should expect climate-change-driven heat, drought, and low flows to exacerbate algal problems on the Columbia. Climate change coupled with excessive nutrient pollution may cause more intense blooms that occur more often. Columbia River dams that slow flows and increase water temperatures are significant contributing factors as well.

This doesn’t sound good. Who is responsible for monitoring?

Neither Oregon nor Washington have statewide HAB monitoring systems. In general, any sampling is done on a volunteer basis at the discretion of designated management agencies (such as cities, counties, the U.S. Army Corps of Engineers, the U.S. Forest Service, or parks and recreation departments). But resources are limited. As Oregon Health Authority (OHA) states, “these agencies have little to no dedicated financial and staff resources to carry out sampling and analysis throughout the season.” They go on to say that most waterbodies in Oregon are not monitored. In Oregon, OHA is responsible for issuing health advisories when the available data exceed safe limits, but OHA doesn’t have the authority to require agencies to monitor, even when it is highly recommended.

Is Columbia Riverkeeper monitoring HABs?

Columbia Riverkeeper is not currently sampling or monitoring harmful algal blooms for toxins. However, we will do our best to inform the public in cases where harmful algal blooms have been identified. 

How will I know if a bloom is toxic?

Not all algal blooms are toxic but, unfortunately, you can’t tell just by looking. Sampling and testing are required to determine if toxins are present. Being aware of local health advisories is important, but if the water looks scummy or pea green, people and pets should avoid water contact. The motto is: “when in doubt, stay out!”

What can we do to help?

To prevent toxic algal blooms, we need to reduce nutrient inputs from industrial chemicals, fertilizers, manure, and human waste; increase water flow; address the temperature impacts of dams; and curb climate change. Even small changes from individuals can help, like always remembering to pick up pet waste and adopting practices to reduce nutrient pollution (e.g. taking care to not over-fertilize). Reducing stormwater runoff and protecting riparian habitat help too since nutrient pollution in runoff can trigger HABs. We also need to increase monitoring and develop better communication systems to protect people, pets, wildlife, and the environment.