The Light Environment and Cellular Optics of the Snow Alga Chlamydomonas nivalis (Bauer) Wille†¶

Abstract

The alga Chlamydomonas nivalis lives in a high-light, cold environment: persistent alpine snowfields. Since the algae in snow receive light from all angles, the photon fluence rate is the critical parameter for photosynthesis, but it is rarely measured. We measured photon irradiance and photon fluence rate in the snow that contained blooms of C. nivalis. On a cloudless day the photon fluence rate at the snow surface was nearly twice the photon irradiance, and it can be many times greater than the photon irradiance when the solar angle is low or the light is diffuse. Beneath the surface the photon fluence rate can be five times the photon irradiance. Photon irradiance and photon fluence rate declined exponentially with depth, approximating the Bouguer-Lambert relationship. We used an integrating sphere to measure the spectral characteristics of a monolayer of cells and microscopic techniques to examine the spectral characteristics of individual cells. Astaxanthin blocked blue light and unknown absorbers blocked UV radiation; the penetration of these wavelengths through whole cells was negligible. We extracted astaxanthin, measured absorbance on a per-cell basis and estimated that the layer of astaxanthin within cells would allow only a small percentage of the blue light to reach the chloroplast, potentially protecting the chloroplast from excessive light. ‡Abbreviations: CCD, charge-coupled device; PAR, photosynthetically active radiation.

Spectral Signatures of Photosynthesis. I. Review of Earth Organisms

“…They are often the first colonizers on rock substrate and can be the dominant source of net primary productivity and a source of food for animals in some land ecosystems (Ager, et al, 1987;Rees, et al, 2004), in some cases accounting for 70% of the land cover (Solheim, et al, 2000). The extreme temperature limits of photosynthetic organisms range as low as -15.7 ºC, the survival limit for arctic snow algae and arctic ice shelf cyanobacteria (but they require liquid water for growth) (Gorton, et al, 2001;Mueller, et al, 2005) and as high as ~75ºC for bacteria in hot springs (Miller, et al, 1998). Meanwhile, the temperature limits for Earth life in general can be as low as -20 (Junge, et al, 2006) and possibly as high as 120 °C (Kashefi and Lovley, 2003).…”

A Community of Clones: Snow Algae Are Diverse Communities of Spatially Structured Clones

“…Frequently, these snow algal blooms are visually red but can also be green or yellow depending on which algal species dominates the community. Red-pigmented algal blooms result from the enormous cell density of primarily Chlamydomonas nivalis or Chloromonas nivalis, whose red color is a result of astaxanthin (Müller et al 1998), a secondary carotenoid, and its fatty acid ester derivatives (Gorton et al 2001).…”

Fungi and Algae Co-Occur in Snow: An Issue of Shared Habitat or Algal Facilitation of Heterotrophs?

“…These algae often produce colonies that are visible to the naked eye as a result of their characteristic red color. The red color of these algae is a result of the secondary carotenoid astaxanthin (Müller et al, 1998) and its fatty acid ester derivatives (Gorton et al, 2001) produced in large quantities during their diploid, zygotic stage that is also characterized by thickened cell walls that are resistant to harsh environmental conditions including repeated freezing temperatures (Hoham, 1980;Remias et al, 2005Remias et al, , 2010. During the warm season in small meltwater pools, the zygotes undergo meiosis, producing haploid offspring that are green, are metabolically active, and multiply asexually.…”