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The optimum temperatures of three species of snow algae were studied using four strains of Chloromonas (Cr.) rosae v. psychrophila, six strains of Cr. tughillensis, and one strain of Cr. chenangoensis. These axenic strains were from Upstate New York except for two of Cr. rosae v. psychrophila from the White Mountains, Arizona. Temperatures tested were from 2.5 to 20°C. The high elevation subalpine Cr. rosae v. psychrophila from New York and Arizona grew from 4 to 20°C and had the greatest cell counts at 4 to 15°C. In contrast, the subalpine to temperate low elevation strains of Cr. tughillensis grew from 2.5 to 10°C and optimally at 2.5 or 5°C, and Cr. chenangoensis grew from 2.5 to 7.5°C and optimally at 2.5 and 5°C. Chloromonas tughillensis and Cr. chenangoensis belong to a genetic subclade with low temperature optima, whereas Cr. rosae v. psychrophila belongs to a subclade with broad temperature optima. In acclimation experiments, there were no significant differences in cell counts when acclimating two Adirondack, New York, strains of Cr. rosae v. psychrophila for two weeks prior to experiments vs. using non-acclimated strains that were moved from 4°C directly to 4, 10, 15, or 20°C. For Cr. tughillensis, four of six strains had significantly higher cell counts when grown at 2.5°C after acclimation at 7.5°C for five months. These are the first reports of temperature optima of snow algae from eastern North America. [ABSTRACT FROM AUTHOR]

Two new species of Volvocalean green snow algae are described from Upstate New York, Chloromonas chenangoensis and Chloromonas tughillensis. According to rbcL sequence analysis, these species belong to a subclade of five snow species of Chloromonas that includes Cr. brevispina, Cr. nivalis and Cr. pichinchae. These species have zoosporangia/gametangia (cell packs) that are propelled by flagella. The life cycles of Cr. chenangoensis and Cr. rughillensis include a change in cell shape from oblong to spherical before the loss of the cell wall. Using 8-h laboratory experiments, a peak in the change of cell shape occurred at 4 h for Cr. chenangoensis and between 2 and 4 h for Cr. rughillensis after the onset of light, and this was followed by a decline in change of cell shape for both species. Spherical cells peaked between 6 and 8 h for Cr. chenangoensis and at 8 h for Cr. tughillensis. Maximum total matings occurred at 4 h for Cr. chenangoensis and 6 h for Cr. tughillensis, which was followed by a peak in quadriflagellate zygotes at 8 h for both species. Mature zygotes (zygospores) were observed only in Cr. tughillensis. [ABSTRACT FROM AUTHOR]