Blue-Green Algae Update Contra Costa Environmental Health
Starting in summer 2015, Environmental Health has responded to citizen complaints about the presence of Harmful Algal Blooms (HABs) in Discovery Bay. The HABs toxin, microcystin, has been found in some of the water samples. In summer of 2016, Environmental Health started routine sampling in various parts of Discovery Bay instead of just conducting complaint sampling.
Discovery Bay waters were sampled for testing on June 27, 2018. The results indicate levels of cyanotoxin that exceed recommended limits. The appropriate Caution and Danger signs have been provided to the Harbor Master for posting.
Environmental Health advises residents and visitors to Discovery Bay to avoid coming into contact with water in affected areas. Avoiding contact with the water is also advised for pets. Based on the results obtained from the EPA and in accordance with state guidance, Environmental Health will post public access areas and advise residents of harmful toxin levels via social media and other electronic communication.
Blooms of blue-green algae, also known as cyanobacteria, can look like green, blue-green, white or brown foam or scum floating on top of water, or suspended in the water. Warm water temperatures and nutrients contribute to blooms, but these will eventually subside under cooler conditions.
CCEH will regularly test bodies of water throughout Discovery Bay and update the community while these conditions persist.
“Anyone who had contact with blue-green algae and has now developed symptoms or believes they may have consumed contaminated water should contact their healthcare provider immediately or call California Poison Control at 1-800-222-1222,” said Underwood.
No illnesses linked to Discovery Bay algae blooms have been reported in 2017. A child became sick after swimming in Discovery Bay during a similar event in 2016. Only recreational water areas are affected. Tap water in Discovery Bay is unaffected by the algae bloom.
For updates, detailed explanations of posted advisories, a map of sampling sites and other information, visit