Probing the Depths of Crater Lake: A Century of Scientific Research by Douglas Larson
Kemmerer and his colleagues also recorded the lake’s temperature gradient and obtained the first measurements of dissolved oxygen and carbon dioxide throughout the water column. They also measured the visibility, or transparency, of lake water by lowering a tour and three-quarter-inch-diameter white Secchi disk into the lake until it disappeared. The disk is named after A. Secchi, an Italian scientist, who devised this technique in 1865; the depth at which the disk disappears from view is referred to as Secchi disk transparency or, simply, the Secchi depth. The Secchi depth at Crater Lake was eighty-two feet on August 1 and eighty-nine feet on September 5, 1913, confirming Diller’s observation about the lake’s considerable visibility. “A white dinner plate 10 inches in diameter may be seen at a depth of nearly 100 feet,” he reported.
Twenty years passed before anyone attempted another limnological study of Crater Lake. The reason for this lack of interest is unknown, but it fit the pattern of sporadic research that continued at Crater Lake for the next fifty years. In 1934, J. Stanley Brode, a biology professor at Santa Monica Junior College in California, proceeded with his own research project to describe the lake’s limnology Brode spent his summers working at Crater Lake National Park as a ranger-naturalist; and from the summer of 1934 through the summer of 1936, he regularly measured lake temperatures from surface to bottom. He also lowered a light meter, a Weston photronic cell, into the lake to determine how deep sunlight penetrated into the lake. He found that sunlight reached a depth of at least four hundred feet due to the water’s high transparency. The presence of sunlight at this depth, and perhaps deeper, explained why phytoplankton could live at great depths in the lake and still have sufficient sunlight available for photosynthesis.