Residents, visitors warned to stay out of Lake Elsinore due to toxic blue-green algae blooms

A dangerous bloom of algae in Lake Elsinore has officials urging people not to get in the water and to stay away from the scum. Valley News/Courtesy photo

Lake Elsinore residents and visitors are warned not to swim in the lake with a large toxic algae bloom erupting in five locations in Lake Elsinore. The West Marina is reporting the largest bloom. The blue-green algae blooms are turning the water green and can be seen from the shorelines along with new “Danger” signage alerting visitors.

The reason for the sudden increase, while not uncommon in the summer, is a major change in the waters since early April when the lake waters were showing signs of improving with no swim advisories. Hoping to improve the water quality, the city of Lake Elsinore is employing some of the latest methods of reducing the blooms including a special new nanobubble treatment.

Yet, because of the recent very high temperatures, a June “Lake Watch” chart showed that microcystin, the most prevalent form of harmful algae cyanotoxin, is rising to very high levels in five areas of the lake as reported by WSP Environment & Infrastructure scientists. The Lake Watch chart showed the ppb (amounts of free hydrogen and hydroxyl ions in the water, measured in nanograms per milliliter or parts per billion) were the worst in the West Marina area. It showed the microcystin level in April stood at 0.60 ppb posing no danger to swimmers, fisherman or boaters. But then on June 12, a WSP reading showed the level had jumped to 36,750 ppb which is very dangerous to living things. This has brought the city of Lake Elsinore to prohibit swimming and fishing in the lake.

That same information even caught the attention of a fish and game environmental advocate in Florida, who called the Valley News to ask why the amazing jump in the Lake Elsinore microcystin levels was well above the troublesome algae blooms in his state. He was told the early hot summer temperatures seem to be the major cause of the larger algae blooms in Lake Elsinore.

The other four areas tested for the toxic microcystin levels ranged from a low of 199 ppb in the center of the lake to 780 ppb at the Elm Grove shoreline, still considered in the “danger area.” A safe level, where swimming can be permitted, is seen at 0.79 ppb or even lower, whereas a danger advisory is triggered at 20 ppb.) The most recent sampling results indicate that the lake contains extremely elevated levels of toxins associated with cyanobacteria, a group of organisms that form harmful algal blooms which can produce potent toxins.

Those blue-green algal blooms with the high levels of toxins pose a significant health threat to humans and pets, according to public health officials. This has prompted the City to post “Danger” signs urging visitors to avoid any water contact and not to not eat any fish or shellfish from the lake.

The State Water Resources Control Board, in conjunction with the Santa Ana Regional Water Quality Control Board also urged the public to stay out of Lake Elsinore until the algae bloom diminishes. This includes even refraining from boating and paddle boarding in the lake.

The City of Lake Elsinore has been regularly testing for HABs in Lake Elsinore, which is particularly vulnerable to HAB outbreaks due to its shallow waters, increasing temperatures, and its history of blooms in the summer months, which are chronicled in the Lake Watch program that can be found online at

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A “DANGER” advisory at Lake Elsinore means:

  • Stay out of the water, including watercraft.

  • Do not let pets and other animals drink or go into the water or go near the scum.

  • Stay away from scum, and cloudy or discolored water.

  • Do not eat fish or shellfish from this water.

  • Do not use this water for drinking or cooking. Boiling or filtering will not make the water safe.

HABs (harmful algae blooms) are associated with health risks, as they produce dermatoxins that can cause itchy skin and rashes, as well as gastrointestinal distress, headaches, agitation and weakness, or even abnormal breathing if HAB material is swallowed while swimming. Dogs and children are most susceptible to exposure because of their smaller body size, increased potential to swallow water while swimming, and tendency to stay in the water longer. Anyone who suspects exposure to HABs should wash themselves, their children and/or dog immediately.

Tony Ault