In August 1912, during a yearlong survey to determine the
chemical composition of Oregon lakes and rivers, Walton Van Winkle and N. M.
Finkbinder of the USGS stopped briefly at Crater Lake to obtain a water sample
for chemical analysis. Based on this first analysis of Crater Lake water, which
was collected from a depth of six feet about one mile from shore, Van Winkle
postulated that the lake's waters were initially acidic but eventually were
neutralized by reaction with alkaline rock material that lined the caldera.
Nevertheless, despite the preponderance of alkaline rock, lake waters remained
slightly acidic. Van Winkle called this a "remarkable circumstance" and
attributed it to the lake's relatively high concentrations of chloride and
sulfate. He concluded that the source of the chloride was rain and snow and that
sulfate was produced by the dissolution of sulfur deposits in the bottom of the
caldera. (14)
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| National Park Service ranger-naturalists are show here planting fish in Crater Lake in September 1932. Photo courtesy of the National Park Service |
During the summer of 1913, fishery biologists of the U.S. Bureau of Fisheries
made other important discoveries about the unusual limnology of Crater Lake.
George Kemmerer, J. F. Bovard, and W. R. Boorman were the first scientists to
collect and identify samples of the lake's microscopic plant and animal life.
They collected water samples from the lake's surface to its bottom with a
deep-water brass sampling apparatus. This device, once filled, was retrieved
from depth and hauled into the boat, where the biologists poured the water
sample through a net capable of catching plankton as small as 76 microns (0.076
millimeters) in diameter. Microscopic plants, or phytoplankton, were found at
depths reaching 650 feet. Two major types were identified: diatoms, which are
single-cell plants with cell walls comprised of silica, and filamentous green
algae. They also found microscopic animals, or zooplankton, including rotifers
and "several" crustacean species, the most common of which were water fleas,
identified as Daphnia pulex.
Based on stomach analyses of fish caught
in the lake, the three biologists determined that water fleas were a major food
source for the lake's rainbow trout. (15)
