Scientists work to keep Oregon’s Crater Lake clear for years to come

On a warm August day, aquatic biologists Scott Girdner and Josh Sprague lie prone on the deck of the research vessel Neuston. Holding life jackets tented over their heads to block the sun’s glare, they gaze into the sapphire depths of Crater Lake, Oregon’s only national park. As they stare, Biological Science Technician Nate Akers operates a cable that lowers a black and white disk deep into the water.

“I’m out!” Sprague calls out, when he can no longer see the disk. Akers lowers the disk a few more meters, then starts pulling it back up.

“Out!” Sprague shouts again, once it comes into view.

This simple but elegant exercise, called the Secchi depth test, is used to measure the transparency of this incredibly clear, incredibly blue lake. The greater the depth at which a person can see the disk, the clearer the water.