Harmful Algae Blooms

By Water Quality Department

Harmful Algae Blooms otherwise know as HAB’s have been a big topic for the Tahoe Keys. We wanted to shed a light on what HAB’s actually are, where the Key’s current levels of HAB’s is, and what the Water Quality team is doing to monitor them. It’s important to first note that not all algae is harmful. There are many different species that all play a role in our ecosystem. However, around the Tahoe area, you may be seeing what is called blue-green algae - which is very common to see during the warmer months of the year. This blue-green algae, also known as cyanobacteria, is defined as a HAB (Harmful Algae Bloom) because it has potential to become toxic to humans and animals. These HAB blooms can grow quickly, especially in warm temperatures, so that is why it is common to see the blue-green algae form in the later months of the summer season. Other factors of stagnant water as well as nutrient dense waters also aid in the growth of this toxic algae.

HAB’s have been detected in multiple areas in Tahoe including Kiva Beach and Taylor Creek. The Lake Tahoe Forest Service has issued cautions for these areas and has detailed statements about what this means for public health and recreation. Lahontan Regional Water Board also has a team responsible for the HAB’s program around South Lake. Information about HAB’s on a regional scale along with a map of current findings can be found on the State of California Water Quality website (mywaterquality. ca.gov). HAB’s are not new for the Tahoe Keys. We have been facing this issue for multiple years because our lagoons are the perfect mix of conditions that the HAB’s thrive in during the summer season. Luckily the TKPOA WQ Team is versed in all things HABs! The team typically takes weekly samples of HABs in the Keys lagoons as eyes are always searching for the first sign of growth. What triggers the sample? The team usually notes the growth visually, as the discoloration, soupy/ paint-like appearance and algal mats in the water begin to form. The water samples are sent to a local laboratory where the water is tested for multiple harmful toxins. If there are non-detects of toxins, then there is no advisory to the public. However, if the toxins are detected and exceed a particular level, then advisory notices are made. The advisory notices range from “Caution” to “Warning” to “Danger.”

Within the Keys, we are currently at the “Caution” advisory level. What does this mean? This means that harmful algae MAY be present in the water. For safety, it is recommended that adults and children do not drink and to stay away from the algae and scum, that animals do not go in or drink the water, and do not eat shellfish from the water. Trigger levels for posting “Warning” and “Danger” signs are detections of higher concentrations of Microcystins, Anatoxin-a and Cylindrospermopsin. See examples of the three different levels and signage below.

As stated in an article, “No harmful algal bloom at Lake Tahoe but public should be aware”, written for South Tahoe Now published on August 19th, 2022: https://southtahoenow.com/story/07/19/2022/no-harmfulalgal-blooms-lake-tahoe-public-should-be-aware

As a reminder, not all algae is harmful but it’s important to keep your eyes open for HABs. If you head to these precautions, you can stay safe and healthy in your area!

“If you see a potential harmful algal bloom, there are things you can do to protect yourself, family and pets. There is no way to tell if an algal bloom is toxic just by looking at it. The California Water Boards recommends that you practice Healthy Habits while enjoying the outdoors at your local lake, river, or stream.

• Heed all instructions on posted advisories if present • Avoid algae and scum in the water and on shore • Keep an eye on children and pets (dogs) • If you think a HAB is present, do not let pets and other animals go into or drink the water, or eat scum and algal accumulations on the shore • If you think a HAB is present, reduce potential for inhalation of sprays or mists by avoiding areas downwind of the bloom, and activities near the bloom that could kick up spray, such as boating at higher speeds, water skiing, or splashing. • Don’t drink the water or use it for cooking • Wash yourself, your family, and your pets with clean water after water play • If you catch fish, throw away guts and clean fillets with tap water or bottled water before cooking • Avoid eating shellfish if you think a HAB is present”