Algal Bloom Contaminates Only Drinking Water Supply in Pacific Crest Trail, California

Hikers on the Pacific Crest Trail (PCT), a 2,650-mile trail that runs through California, Oregon, and Washington from Mexico to Canada, are avoiding a section of the Californian desert due to an algal bloom in the only available drinking water.

The California State Water Board announced the cyanobacterial algal bloom and shared a map of areas where drinking water could be affected. Algal blooms occur when cyanobacteria outcompete other phytoplankton in a body of water and reproduce rapidly as a result of conditions such as warmer temperatures or pollution.

Not Drinkable

Toxins produced by cyanobacteria can be extremely harmful to anyone who consumes them, from humans to dogs. Toxins produced by freshwater cyanobacteria, such as those found in drinking water sources along the PCT, fall into one of two categories. The first is toxins that target the liver (hepatotoxins), and the second is toxins that target the nervous system (neurotoxins).

The Pacific Crest Trail Association (PCTA) has issued warnings to hikers about the risks of drinking algae-affected water, advising them to avoid reservoirs, lakes, springs, tanks, rivers, and streams because the algae can cause illness.

According to PCTA, harmful algal blooms can sometimes be seen as a 'scum' or discoloration on the water surface. They can also be hidden beneath the water's surface or attached to the bottom of a body of water. It can be difficult to tell if a mat contains toxin-producing species by looking at it.

Hikers Accounts

Etienne Goldman, a 24-year-old hiker from the U.K. who is currently in the area, said that he and the rest of his hiking group are skipping a 90-mile stretch of the trail between Tehachapi and Walker Pass after hearing about other hikers getting sick on the FarOut app. Hikers can get alerts and community updates about the trail they're on from FarOut.

Goldman said they saw comments from the PCTA on the FarOut app warning that the water sources were making people sick. They haven't been able to get anyone out to properly test them, but they are believed to be caused by algal blooms.

Goldman says he's heard from other hikers who say they've drunk the water from these "dangerous" sources and been fine, but he doesn't want to risk getting sick in the desert.

Goldman and her colleagues decided to skip that section because getting sick in the desert is no laughing matter when you're 20 miles from the nearest town, the temperature is 100 degrees, and there's no shade. He goes on to say that while there are many differing viewpoints in the app's comments, everyone agrees that you must be comfortable taking risks.

HABs

According to PCTA content development director Scott Wilkinson, the agency is investigating reports of hikers becoming ill, as they are unsure whether the problem is caused by HABs or Harmful Algal Blooms, and agency partners are testing water sources.

According to the California Water Board, exposure to cyanobacteria and associated toxins can cause eye irritation, skin rash, vomiting, mouth ulcers, and diarrhea. Hikers trekking around the Mojave Desert's borders, one of the world's hottest places, with tens of miles of walking between water sources, the last thing they need is to lose water through any other means, Newsweek reports.

According to Wilkinson, the most common filters used by hikers typically filter out bacteria but not toxins in the water. Water drops from trail angels may also help, but hikers should not rely on them. There are currently no plans to close the section.