Lake’s bright green hue shows up on satellite photos of California. What happened?

A satellite photo shows California’s largest freshwater lake has turned green, NASA reported.

The photo, posted May 29 on the agency’s Earth Observatory blog online, shows the bright green hues of Clear Lake in Northern California can be seen from space.

The photo, shot May 15 by the Operational Land Imager-2 on the Landsat 9 satellite, suggests an algae bloom may be causing the discoloration, NASA said.

The bloom could include blue-green algae, known as cyanobacteria, along with other types of phytoplankton, NASA said.

“Only a direct sample can determine the exact composition of a bloom,” the agency said.

Cyanobacteria are responsible for most freshwater harmful algae blooms, the U.S. Geological Survey said. The single-celled organisms can be toxic to humans and animals.

“The algae in Clear Lake are part of the natural food chain and keep the lake fertile and healthy,” Lake County officials said.

The algae keeps sunlight from reaching the bottom of the shallow lake, curtailing the growth of weeds that could “choke off the lake,” officials said.

But blue-green algae blooms can create problems, the county said. Soil samples show such blooms have been part of the lake since the last ice age 10,000 years ago.

Clear Lake is the largest freshwater lake in the state, California State Parks said.

“The area is popular for all kinds of water recreation, including swimming, fishing, boating and water-skiing,” the agency said.

Clear Lake is about a 100-mile drive northwest from Sacramento.

This story was originally published June 2, 2024 at 12:19 PM with the headline "Lake’s bright green hue shows up on satellite photos of California. What happened?."