Pyramid Lake in Nevada has turned into a spooky spectacle this fall with eerie green swirls spreading across its waters, a sight so striking it’s even visible from space. The phenomenon, captured by NASA’s Landsat 9 satellite, is the result of an algal bloom that has painted the 125,000-acre lake with vivid, army-green hues, creating what experts are calling one of the most intense blooms in recent years.
This year’s bloom has been particularly robust, primarily due to high levels of “Nodularia spumigena”, a cyanobacteria species, or blue-green algae, that thrives in the lake’s warm, shallow waters.
The Pyramid Lake Paiute Tribe, which monitors water quality, has attributed this green transformation to warmer temperatures and an influx of nutrients from storm activity in mid-October, which created waves and stirred up algae from the lakebed. According to Aaron Bill, water quality manager for the tribe, the lake now resembles “split pea soup,” a troubling sign given the bloom’s toxic effects.
The vivid green swirls may look almost magical, but they come with a serious warning. Cyanobacteria like “Nodularia spumigena” produce microcystins, toxic compounds that can be highly dangerous if inhaled or ingested, causing symptoms ranging from skin rashes and diarrhea to more severe health risks such as liver and neurological damage.
The cyanobacteria can even release a secondary toxin, nodularin, which is especially damaging to the liver and can lead to hemorrhaging and severe illness if consumed in high quantities. Because of the risks, the tribe has advised visitors to avoid any contact with the water and keep pets at a distance.
This is not Pyramid Lake’s first experience with algal blooms, which typically occur in the summer or fall. The lake’s unique ecology makes it especially susceptible. As a remnant of the ancient Lake Lahontan from the last ice age, Pyramid Lake has retained its shallow, nutrient-rich waters.
This characteristic, combined with warm temperatures, sets the perfect stage for algal blooms, which thrive in shallow, stagnant environments. When storms hit in October, they broke up the bloom, allowing it to disperse and settle near the lake’s surface, amplifying its visibility.
Water samples taken by the San Francisco Estuary Institute confirmed that levels of chlorophyll-a and cyanobacteria peaked in mid-October, indicating heightened algal activity. While algal blooms play a natural role in lake ecosystems, providing nutrients and helping limit invasive aquatic plants, the effects can quickly turn hazardous.
When algae concentrations get too high, they block sunlight and decrease oxygen in the water, which can harm native fish species, like the endangered cui-ui, which rely on Pyramid Lake as their last remaining habitat.
The good news? The Paiute Tribe believes conditions will begin to stabilize within the next two to three weeks as microcystin levels taper off. For now, the lake serves as both a cautionary reminder of the impacts of climate and nutrient changes on our freshwater resources and a vivid example of nature’s power to transform entire landscapes.
