Observations on Snow Algae in California1,2

SUMMARY Algae that impart a red color to snowfields are rather common in California. Red snow occurs mainly in the Sierra Nevada at altitudes of 10,000–12,000 ft (3050–3600 in) and can occur at high altitudes where snow persists in other parts of the state. The distribution in the Sierra was similar in 1969 and 1970, contrasting snowfall years. Colored snow was found from May to October in old, wet snow‐fields. The predominant color was red and occurred as surface patches in depressions in the snow. The color could extend as deep as 30 cm below the snow surface. Algae in the snowfields of the Tioga Pass area (Sierra Nevada) were large, red, spherical cells of Chlamydomonas nivalis. No other algae were seen. Their distribution, as measured by cell numbers and chlorophyll a, was patchy. Algal cells and chlorophyll a were mainly distributed at or near the snow surface but extended down to a depth of 10 cm. Light intensity was greatly attenuated by snow, but enough light for photosynthesis was found at 50 cm below the surface. Nutrient content of one snow sample was very low. The populations were very actively photosynthetic and took up as much as 65% of added 14CO2 in only 3 hr. It was tentatively concluded that CO2 limits in situ photosynthesis. Photosynthesis was inhibited by melting snow samples. Rough calculations of the growth rate suggested in situ generation times of only a few days for these algae.