California's largest freshwater lake has turned a lurid green thanks to a huge algal bloom, as seen in pictures taken from space.
Situated around 120 miles north of San Francisco, Clear Lake has long been plagued by significant algal blooms, prompting environmental and health concerns.
Now, in images taken by the OLI-2 (Operational Land Imager-2) on the Landsat 9 satellite on May 15, the lake can be seen shining a bright green as a result of one of these algal blooms.
Clear Lake covers an area of about 68 square miles and is the oldest lake in North America at about 500,000 years old. It supports large populations of fish and attracts numerous bird species, including ducks, pelicans and bald eagles, making it a popular spot for wildlife enthusiasts. The lake regularly experiences algal blooms as its warm waters and shallow depths make it a prime breeding ground for algae.
Algae blooms in Clear Lake are primarily caused by cyanobacteria, also known as blue-green algae. These single-celled organisms thrive in nutrient-rich environments, particularly when phosphorus and nitrogen are abundant.
"These excess nutrients can cause harmful algal blooms (HABs). This is a bust or boom scenario whereby blue-green algae, for example, will proliferate and utilize all of the available dissolved oxygen," Ian Hendy, a senior scientific officer at the Institute of Marine Sciences of the University of Portsmouth in England, told Newsweek.
This is often exacerbated by agricultural runoff and other human activities like mining and sewage treatment, as these increase the levels of nutrients in the water, sparking more severe and more regular algal blooms.
On May 15, which is the same day that the picture was taken, levels of chlorophyll-a, a chemical used by algae and plants to harvest light energy, reached some of the highest levels of the month within the waters of Clear Lake.
Over 130 species of algae have been detected in the waters of Clear Lake, three of which can be harmful to human health. According to a NASA Earth Observatory statement, some of the algae in Clear Lake can produce toxins such as microcystin, which pose serious health risks to both humans and wildlife. Microcystin can cause skin irritation, liver damage and even kidney failure if ingested.
Even if these toxins aren't present, algal blooms can sap all the oxygen from water and potentially cause fish and other life to asphyxiate.
"This process creates very low oxygen levels in the water, making life for aquatic organisms such as fish and invertebrates very dangerous," Hendy said.
Algal blooms in Clear Lake have significant ecological and recreational implications, as residents and tourists are advised to avoid water activities such as swimming and fishing because of the potential health risks. The visual impact of the blooms also deters visitors, impacting tourism and the local economy.
Clear Lake is not unique in facing these challenges, with similar issues recently observed in other large bodies of water, such as Lake Winnipeg in Canada and Lake Okeechobee in Florida. Both lakes have experienced severe algal blooms because of a combination of warm temperatures and nutrient-rich runoff.
The situation at Clear Lake highlights the broader environmental challenges posed by nutrient pollution and climate change. As water bodies warm and nutrient levels increase, the frequency and severity of algal blooms are expected to rise, necessitating concerted efforts to protect water quality and public health.
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