Algae are a natural part of the lake’s ecosystem. However, when conditions are right, they can form harmful algal blooms (HAB). These blooms can produce toxins that may harm people and animals.
HABs can be mistaken for harmless types of algae that naturally occur in Tahoe and can be found clinging to rocks, washing up on beaches, and attached to the bottom of creek and river channels.
These blooms often look like green paint or thick mats floating on the water or sitting on the bottom. Dogs are especially at risk because they may drink the water or lick the algae off their fur.
Common factors contributing to algal blooms are warmer temperature, slow or stagnant water, and nutrients in the water that serve as food for algal organisms.
The water board relies on three tiers of signage to inform the public about HABs. From lowest to highest, they are caution, warning, and danger. These signs, or advisories, recommend what you should and should not do in areas experiencing a HAB. Advisory levels typically apply to specific affected areas, such as one beach or portion of a beach, and not an entire waterbody.
This season, El Dorado Beach, Regan Beach, Kiva Beach, and Kings Beach will be tested before the Fourth of July and Labor Day to help keep the public informed of potential risks.
If you see water that looks suspicious, avoid contact and report it to the water board. You can check current conditions online.
To help protect the lake, clean and dry boats and gear after use, and report what you see at CitizenScienceTahoe.org.
