Toxic algae threaten ‘gem of Chico’ – and these 10 waterways in the greater Sacramento area

The lake visitors call the “gem of Chico,” the local go-to location for a quiet and relaxing day trip on the waterfront, is infested with toxic algae, officials say.

The Butte County Public Health Department warned people on Monday to stay away from Horseshoe Lake after colonies of microscopic cyanobacteria grew out of control and ‘bloomed’ into toxic and potentially lethal algae, poisoning the waterway.

Harmful algae blooms, or HABs, are not new to the area – or to the Central Valley. This is the second alert of freshwater HABs recorded in the past 30 days in Butte County, and the 15th this year in the Valley.

While Sacramento County has less exposure to these toxic algae than other regions in California, local lakes are not safe from HAB exposure either, according to a report by the Sacramento Environmental Commission. “There is present a risk which may increase with higher temperatures, more frequent low flow conditions, and higher frequency of drought,” the commission warned in 2016.

In 2017, Laguna Joaquin in Rancho Murieta and the Stone Lakes national wildlife refuge in southern Sacramento County were affected by HABs. And just last summer, HABs were detected in Sacramento Lake near the Freeport Intake, in the Port of West Sacramento near the Washington Lake entrance, and in Arcade Lake.

The state’s Water Quality Monitoring Council collects and maps reports of HAB-related incidents, providing a better understanding of which areas are at greater risk of infestation. However, the council emphasizes that the “map only shows locations where harmful algal blooms (HABs) have been voluntarily reported... [and] a waterbody with no data is not an indication that a bloom is not present.”

The commission identified 10 waterways in the greater Sacramento area that pose a higher risk of HAB exposure:

  • American River

  • Sacramento River

  • Cosumnes River

  • Morrison Creek Group

  • East Drainage Canal/ Steelhead

  • Creek/Dry Creek/ Arcade Group

  • Deer Creek Group

  • North Fork Badger/ Laguna Creek/ Deadman/ Bear Slough Creek

  • Delta Waterways and Sloughs

  • Folsom Lake

HABs have existed for millions of years and are essential to the freshwater ecosystem, according to a news release by the Butte County Public Health Department. However, since HABs thrive in “warm weather, stagnant water flows and excessive nutrient inputs,” more recent weather patterns caused by climate change and pollution are favoring their growth.

According to the National Oceanic and Atmospheric Administration, as greenhouse gas levels continue to rise, coastal and lake-rich states will have to confront HABs in more waterways and more frequently.

They are a national concern, the NOAA reported in 2018, because they threaten both public health and the economies of coastal communities that rely on fishing and tourism.

NOAA says 25 percent to 75 percent of HABs are toxic and “can present risks of illness and mortality at environmentally relevant concentrations.” They can poison humans and animals who come into contact with them through infested waterways, or ingest fish and shellfish in which the bacteria have accumulated.

Children and small pets are at higher risk of exposure because of their small size. In 2017, HABs killed two dogs in Napa County Pond.

Symptoms of infection include:

  • Sore throat or congestion

  • Coughing, wheezing, or difficulty breathing

  • Red, or itchy skin, or a rash

  • Skin blisters or hives

  • Earache or irritated eyes

  • Diarrhea or vomiting

  • Agitation

  • Headache

  • Abdominal pain

If you think that you or your pet has been in contact with cyanobacteria, get medical treatment immediately.

A bill moving through the California Legislature would coordinate HAB monitoring, notification, response and public outreach. AB 834, sponsored by Assemblyman Bill Quirk, D-Hayward, has passed the Assembly and was scheduled for a committee hearing Wednesday.

You can help authorities better respond to HAB infestation by reporting any suspected HAB or potential HAB-related illness online. You can also call the California Water Quality Monitoring Council coordinators at (916) 341-5357 or (844) 729-6466 (toll-free), or contact them via email at CyanoHAB.Reports@waterboards.ca.gov.

Editor’s note: This story was updated July 3, 2019, to include information about Assembly Bill 834.

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Caroline Ghisolfi, from Stanford University, is a local news reporter for The Sacramento Bee, focusing on breaking news and health care. She grew up in Milan, Italy.