Tioga Pass revisited: Interrelationships between snow algae and bacteria

Previously (1969-70) snow algae were studied at Tioga Pass, Sierra Nevada, California. Red snow algae were identified; their distribution was patchy; and they were actively photosynthetic. In July-August 1993, red snow patches were abundant in this same area and biological comparisons were made between red and non-colored snow. Algal cells were often about 750 times more abundant in red snow than in white snow; and no chlorophyll was detected in white snow while red patches contained up to 0.1 µgm chlorophyll mL /snow. Bacterial abundance in white patches were only one-third to one-eight those in red snow and dissolved organic carbon was also lower. In red snow the incorporation rates of ³H-leucine into bacterial protein were 103-295 times less than algal photosynthesis rates when both were expressed as µgm C taken up mL/snow/h. Bacterial production rates were also lower in white snow than in red snow. These results suggest that bacteria were intimately associated with algae in the snow and that bacteria may have been utilizing carbon excreted by the algae. This hypothesis needs to be confirmed by labeling algae with radioactive carbon, isolating the C-14 excreted by the algae, and feeding it back to bacteria in snow patches.