California’s Oldest Lake Has So Much Algae that You Can See it From Space

California’s Clear Lake is experiencing a significant algae bloom, so severe that it is visible from space, according to recent satellite images captured by NASA in mid-May. These images suggest the lake may be infested with blue-green algae, or cyanobacteria, which can be harmful to humans and animals, as noted by the United States Geological Survey.

While algae play a crucial role in maintaining the health of freshwater ecosystems, Clear Lake’s current condition highlights a problematic overgrowth. County officials have identified more than 130 different species of algae in the lake. Three specific species of blue-green algae are known to cause harmful blooms, particularly in the spring and late summer. These blooms can lead to skin irritation, gastrointestinal issues, and neurological symptoms.

Located about 100 miles north of San Francisco in Lake County, Clear Lake has seen an increase in harmful algal blooms in recent years. Historically, Clear Lake lived up to its name with clear waters, but since 1925, the water has become increasingly murky, largely due to human activities.

NASA’s analysis indicates that runoff from farms, vineyards, faulty septic systems, gravel mines, and an abandoned mercury mine has significantly impacted the lake’s water quality. The lake has also faced issues such as mercury contamination, pesticide usage, invasive species, and high levels of primary production. Invasive carp further disturb the lake’s sediment during spawning and foraging, exacerbating the problem.

Future conditions may favor even more frequent toxic algal blooms. Researchers warn that rising seasonal water temperatures could promote the dominance of cyanobacteria. To determine if the current bloom is harmful, a sample will need to be tested. Nonetheless, the abundance of algae can deplete oxygen levels in the water, creating dead zones that can kill fish and other aquatic life. The Environmental Protection Agency notes that the largest dead zone in the U.S. is in the Gulf of Mexico, spanning 6,500 square miles each summer due to pollution from the Mississippi River Basin.

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