Department of Public Health Issues Warning: Harmful Algal Blooms in Lake Havasu

MOHAVE COUNTY, AZ (January 28, 2025) – Mohave County was notified by the Arizona Department of Environmental Quality (ADEQ) in mid-December regarding multiple Harmful Algal Blooms (HABs) in Lake Havasu, as reported by the Bureau of Reclamation (BOR). These blooms were discovered during BOR’s quarterly monitoring trip on December 3, 2024.

The BOR collected samples that were sent for testing to determine toxicity. Testing results received this week indicated non-detectable or very low levels of algal toxins at the time of sampling. The BOR noted that while the concentration of phytoplankton was somewhat high for this time of year, it was not unusual compared with other measurements over the last decade. However, the BOR also mentioned that samples taken were from open water locations, meaning the most problematic areas around the lake may not have been captured. Algal toxins tend to be highest in sheltered coves, beaches, and boat ramps.

Residents and visitors to Lake Havasu are advised to remain vigilant for potential increases in HABs in these types of sheltered areas.

HABs occur when algae, a naturally occurring aquatic organism, grow rapidly in a short period. They can manifest in water as:

– Pea soup or spilled green paint
– Discoloration or streaks
– Surface scums, mats, or films
– Green dots or globs floating below the surface

For more information and frequently asked questions about HABs, please visit the ADEQ website at [ADEQ Website](https://www.azdeq.gov/AZHABs). Locations of the blooms at the time of sample collection are indicated by a red dot on the map.