NASA Makes Unexpected Discovery in One of California’s Largest Lakes

By: Beth Moreton | Published: Jun 18, 2024

While NASA’s Landsat 9 satellite was capturing images of one of California’s largest lakes, Clear Lake, it made an unexpected but important discovery. 

The lake had turned bright green in color and was clearly visible from space. However, the satellite images revealed that this green color in the lake is possibly due to an algae bloom.

Clear Lake Is Popular With Boaters and Swimmers

Clear Lake is one of the oldest lakes in California. It is located 60 miles north of San Francisco Bay and is most commonly used for boating, swimming and fishing.

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Brown wooden boats on a lake with people using oars to move them.

Source: Pietro De Grandi/Unsplash

However, due to the dangers this algae bloom poses to humans, it is unlikely that these activities will be carried out over the next few weeks while the algae is treated and removed.

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Clear Lake Supports Wildlife Systems

One important aspect of Clearlake is its support of wildlife systems. At 500,000 years old, it has supported these systems for that time but now poses a danger to them.

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A school of silverfish in the water.

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The wildlife supported includes large populations of fish and various species of birds, including ducks, pelicans and bald eagles. However, some of these (fish in particular) have been found dead due to the water’s algae.

Algae Causes Low Oxygen Levels

One reason wildlife dies in these waters is the toxins the algae produces. The algae also causes low oxygen levels in the water, leaving wildlife unable to breathe.

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A green body of water, which is caused by algae.

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This highlights serious environmental challenges regarding climate change and nutrient pollution, especially as warm temperatures cause algae to grow.

The Algae Has Become More Common With Human Activity

Blue-green algae, known as cyanobacteria, has been somewhat common throughout Clear Lake’s very long history. However, due to human activity, it has become increasingly common over the last century.

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A body of water that is turning green due to algae. Some ducks are swimming in the water.

Source: Liz Harrell/Unsplash

This algae can come from runoff from nearby farms, vineyards, faulty septic systems, gravel mines, an abandoned open pit from a mercury mine or a non-native carp that has stirred up nutrients in the sediment of the lake’s bed.

Algae Typically Blooms During Summer Months

Algae need warm weather to thrive and typically bloom during the summer months. This is something that has happened throughout Clear Lake’s history.

A body of water turning green due to algae. Some trees are in the background.

Source: Jordan Whitfield/Unsplash

However, as this bloom happened just before the summer months, it is the earliest it has happened and at one of the worst levels ever recorded. It is likely a result of warmer weather outside of the summer months due to climate change.

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The Harmful Impact of Algae Blooms

There are several effects that algae blooms can have on people, many of which are harmful, and this is why all activities in the lake have been banned until the problem has been resolved.

A body of water that appears clear on the top but is green underneath due to algae. Rocks are at the bottom of the water.

Source: Saketh/Unsplash

Some species of cyanobacteria release toxins that can damage the liver. Contact with the algae can cause various symptoms, such as headaches, eye irritation and wheezing.

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The Cost of Algae Blooms

The cost to health isn’t the only thing to worry about with these algae blooms. There is also a cost to the rest of the nation’s economy to deal with them. This cost is upward of $50 million annually.

A body of water turned green due to algae.

Source: Jordan Whitfield/Unsplash

This includes costs related to health, fisheries, recreation, tourism and monitoring. As around 1,200 lakes and rising in the U.S. have this algae, this cost is only expected to increase over the next few years.

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Testing Algae at Clear Lake

The Big Valley Band of Pomo Indians has been testing water since 2014. As part of the water testing, they know which times of year the algae is likely to be more prevalent.

A body of water with large patches of green on the surface due to algae.

Source: Michael & Diane Weidner/Unsplash

This is the earliest time of year in the last decade when algae bloomed. At this time, the water has turned the typical bright green, but it is also among the worst bloomings of algae that Clear Lake has seen.

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The Algae Bloom Grew Rapidly in a Week

The lake’s toxicity levels were initially measured on May 8, just one week before the NASA images showed how green the water was. At this point, no bloom was shown.

A green algae bloom seen in the ocean

Source: oceanservice.noaa.gov

The lake was also compared to the same time in 2023. The results were quite clear, as was the water in 2023, whereas the water in 2024 was bright green.

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A Water Quality Analysis Tool Was Used

Initial tests were carried out on the water using a water quality analysis tool. The tool showed levels of chlorophyll-a, a sunlight-harvesting pigment in plants and phytoplankton, along with an index estimating cyanobacteria concentration that increased throughout early May.

Boats parked at bays at Clear Lake in California. The water is green due to the algae.

Source: @kentphotos/X

These estimates were calculated using an ocean color instrument on Sentinel-3. The NOAA National Ocean Service also used additional processing, which showed that the water levels had reached their highest in May.

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Testing Needs to Be Done on the Algae

As phytoplankton were also found within the water, further testing must be done to establish what types of bacteria are in Clear Lake.

An image of Clear Lake. The water is green due to the algae. In the distance are some hills. Some houses surround the lake.

Source: @CGTNOfficial/X

Once this testing has been completed, it will be known exactly how the water can be treated to get rid of the algae and phytoplankton, with hopes that it doesn’t cause as much of an issue in the future.

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How Does Climate Change Affect Algae Blooms?

According to the Environmental Protection Agency (EPA), global warming creates higher water temperatures. This higher-temperature water combines with runoff from more frequent storms that occur as a result of climate change.

Storm clouds gather over an ocean.

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These two factors work together to deliver more nutrients to the algae, causing them to bloom more intensely and more often.

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Why Are Water Temperatures Rising?

Water temperatures rise in response to higher air temperatures in the atmosphere. Under the theory of global warming, warm air that would normally escape Earth’s atmosphere becomes trapped by “greenhouse gases” like carbon dioxide.

A view of the Indian Ocean during sunset underneath a cloudy blue sky.

Source: Jeremy Ducray/Unsplash

Since this air has nowhere to go, it becomes reintegrated into Earth’s weather systems and is eventually transferred into the ocean.

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Affecting Water Quality

The effects of global warming, and in this particular case increased algae blooms, can harm water quality. As stormwater mixes with cleaner water sources, it can become harmful to drink.

A close-up photo of a person holding a clear glass filled with water. The focus is on the glass and the person's fingers

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Individuals with respiratory conditions must be extremely careful when drinking possible algae-contaminated water to avoid the toxins inflaming their condition.

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Algae and Asthma

A study published by Environmental Health Perspective (EHP) researched how airborne toxins from algae can trigger symptoms of asthma in humans.

A man wearing glasses and a beige blanket coughs into his hand

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“Adverse health effects from harmful algal blooms have most frequently been linked to eating fish or shellfish that have accumulated algal toxins. However, people have also suffered asthma-like symptoms after inhaling minute amounts of algal toxins that were aerosolized by waves,” said the study.

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Sea Sick Lungs

The phenomenon of algae-induced asthma is termed “sea-sick lungs” and the study focused on examining an algae bloom colloquially known as Florida’s “red tide.”

An image depicting a serene sunset over the ocean, with the sun partially obscured by clouds

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Red tide algae contain multiple types of brevetoxins that can cause symptoms like “numbness, tingling, and gastrointestinal distress.” Persons exposed to aerosolized brevetoxins may suffer “shortness of breath, sneezing, and other allergy- and asthma-like symptoms. Persons with preexisting airway disease appear most likely to be affected.”

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Using Sheep

The EHP study utilized sheep to serve as surrogates for respiratory-compromised people and those with asthma-like symptoms.

Two sheep stand next to each other in a field.

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“To study airborne toxin exposure in a more controlled setting, the research team used a sheep model of asthma. The sheep model used is naturally sensitive to an antigen derived from the roundworm Ascaris suum, developing asthma-like symptoms (such as airway constriction) when exposed to this antigen. The sheep therefore can serve as surrogates for persons with asthma,” said the study.

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Unique Microbe

In 2005, researchers discovered unique blue-green algae living in California’s Salton Sea, another giant California lake, that uses near-infrared light for photosynthesis.

A rock sitting in water with algae growth on it.

Source: Dave Hoefler/Unsplash

“This new strain of Acaryochloris is unique because it is able to live on its own,” said UO biology professor Michelle Wood.

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History Repeats

In 2021, CNBC reported that the toxic fumes from the Salton Sea had become an environmental disaster that turned the once popular tourist spot into a ghost town.

A view of the green color of Salton Sea, a landlocked lake in California.

Source: Tuxyso / Wikimedia Commons / CC BY-SA 3.0

At the time, the article warned that the fate of the Salton Sea could be a preview of what will happen in other communities across the western U.S. as water supplies become less predictable with climate change.

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Shrinking Water

The city near the Salton Sea saw many of its homes demolished or unfinished as a result of shrinking water resources at the lake due to climate change. Toxins from algae blooms also contributed to the lake’s decline.

An aerial view of a white boat driving through very dark blue water.

Source: Jordan Cormack/Unsplash

“People here used to fish, swim, bring their boats,” said Frank Ruiz, Audubon’s Salton Sea Program Director, as he stood by a crumbling dock on land that once held water. “They went from living in paradise to living in hell.”

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Avoid Water Contact

Also in 2021, the California State Water Resources Control Board issued guidance advising people and their pets to avoid water contact at the Salton Sea Lake.

A silver tap with running water coming out of it. The spray is coming off the water.

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“A warning for people and their dogs to avoid water contact in the Salton Sea has been issued after the detection of Harmful Algal Blooms at numerous sites and the recent report of a dog that died soon after a swimming excursion…The confirmed presence of HABs around the Salton Sea indicates the blooms contain varieties of toxic cyanobacteria,” said the guidance.

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What is Cyanobacteria?

Cyanobacteria is the technical term for blue-green algae that share some similarities with plants. These bacteria are responsible for the toxic algae blooms that contaminate water in places like Salton Sea Lake and Clear Lake.

A look at cyanobacteria of blue green algae being eaten.

Source: Wiedehopf20/Wikimedia

Some species of cyanobacteria are unique because they can regulate their own buoyancy levels, allowing them to rise to the surface to form thick surface scum. This property, along with greater cyanobacteria levels, might be what allowed the recent algae bloom at Clear Lake to be observed from space.

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Continued Threat

The most recent data on climate change from the National Oceanic and Atmospheric Administration (NOAA) shows that the combined land and ocean temperature metric is continuing to increase at a rate three times as fast as it was in 1982.

Silhouette of multiple smokestacks at an industrial facility emitting thick smoke against a vibrant orange sunset, reflected over a calm body of water

Source: Marek Piwnicki/Unsplash

As global temperatures continue to increase, it will no doubt lead to more frequent and destructive algae blooms that will threaten America’s water resources for years to come.

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