A massive, dangerous bloom of algae has spread through Discovery Bay, a community about 60 miles from San Francisco. And it’s threatening the way of life for the community there — the colorful algae that fills the bay may not look harmful, but it can be extremely dangerous to both people and pets.

The algae blooms have only gotten worse in recent weeks, and it may be part of a string of algal blooms nationwide that are worrying to scientists and authorities, according to an SFGate report.

Health authorities have warned residents to avoid contact with the water at Discovery Bay, and that includes pets, as tests indicate that cyanobacteria (blue-green algae) is present. This algae produces a toxin that can result in rashes, irritate the eyes and cause gastrointestinal problems. Although it doesn’t usually result in deaths for humans, it often kills dogs who drink it up.

The algae hasn’t just affected this California community. Blue-green algae has resulted in b each closures in Florida and in the Lake Erie area it has resulted in the contamination of drinking water.

Scientists have noted that the algal blooms are growing in frequency. They love warm sunshine and lots of pollutants, which they feed on. While many of the algal blooms are likely natural events, human activities like fertilizers and septic runoff are probably feeding more of them.

Last month, researchers in Finland developed an easy to use blue-green algae test that should help ordinary consumers to check to see if the water at their beach is free of cyanobacteria.

“The cyanobacteria test requires only a few drops of water and indicates the result within 15 minutes. If two red lines appear on the display, the water contains cyanobacteria toxins. One line means that the water sample is toxin free,” explains VTT Senior Scientist Liisa Hakola.