Both Big Bear Lake and Lake Silverwood, two of San Bernardino County’s major bodies of water, have been plagued in recent weeks with potentially unhealthful algae blooms.
State, regional and local water boards urged boaters, swimmers, dog owners, fishers and everyone else to avoid direct water contact while visiting areas of both lakes due to the condition.
The areas affected by the bloom at Big Bear Lake include the North Shore, running for roughly a half-mile west of the Big Bear Solar Observatory, and the west side of Stanfield Cutoff, with toxins generally confined near the shore. At Lake Silverwood, bloom conditions have been mercurial, migrating rapidly, with wind and waves pushing the bloom into different portions  of the reservoir, and likewise impacting the concentrations of the algal material.
The phenomenon arises from  organisms known as blue-green algae or cyanobacteria, which will concentrate and accumulate into mats and scum, form foam at the surface and along the shoreline. While it generally ranges in color from blue to green, it sometimes manifests as white or brown.
Cyanobacteria or microcystis aeruginosa is a single-celled blue green alga which produces several strains of toxins. Microcystis can proliferate to combinate into multiple toxins, including the potent liver toxin, microcystin.  When microcystis die, their cells break open, releasing the toxin microcystin into the water.  Ingestion of water or algal cells containing microcystin has produced adverse effects a wide cross section of animals, including fish, dogs, cats, livestock and humans.
Microcystis blooms are typically well-hosted in warm, turbid, and slow-moving water. Water that is high in nitrogen or phosphorus, known as eutrophic waters, supports blooms with the highest biomass.  Microcystis require substantial light intensity to facilitate blooming. In Southern California, cyanobacteria proliferate in the early summer through late autumn and may last for up to four months.  Occasionally, microcystis may be present in the water without apparent blooms on the surface, with the blooming taking place beneath the water.
In humans, algae bloom toxins typically result in gastrointestinal symptoms including nausea, vomiting and diarrhea, as well as eye and ear infections, earache, sore throat, blisters, muscle weakness and pain.
In dogs, cyanobacteria can cause vomiting, stumbling and falling, foaming at the mouth, diarrhea, convulsions, lethargy and sudden loss of appetite, tremors and seizures.