EVIDENCE A PHOTOPROTECTIVE FOR SECONDARY CAROTENOIDS OF SNOW ALGAE<sup>1</sup>

Bidigare, Robert R.; Ondrusek, Michael; Kennicutt, Mahlon C.; Iturriaga, R.; Harvey, H. Rodger; Hoham, Ronald W.; Macko, Stephen A.

doi:10.1111/j.1529-8817.1993.tb00143.x

Cited by 222 publications

(146 citation statements)

References 34 publications

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“…1) demonstrated previous observations [16][17][18][19][20][21][22][23][24] that the appearance of red snow coincides with increased melt rate and temporal trends in melt predictors (Fig. 1a).…”

supporting

confidence: 72%

“…Thus, snow algae increase liquid water availability through 'bioalbedo' 18 , determined by the absorptive properties of their photosynthetic and secondary pigments. The chlorophylls and carotenoids in red-snow algae-particularly the heat-dissipating tetraterpenoid astaxanthin that colours cells red as protection from excess radiation 23,24 -reduce snow-surface albedo in the visible spectrum. Nutrient depletion in the snowpack triggers production of carotenoids 20 in non-motile cells that ultimately overwinter as buried cysts.…”

mentioning

confidence: 99%

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The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

et al. 2017

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A lack of liquid water limits life on glaciers worldwide but specialized microbes still colonize these environments. These microbes reduce surface albedo, which, in turn, could lead to warming and enhanced glacier melt. Here we present results from a replicated, controlled field experiment to quantify the impact of microbes on snowmelt in red-snow communities. Addition of nitrogen-phosphorous-potassium fertilizer increased alga cell counts nearly fourfold, to levels similar to nitrogen-phosphorusenriched lakes; water alone increased counts by half. The manipulated alga abundance explained a third of the observed variability in snowmelt. Using a normalized-di erence spectral index we estimated alga abundance from satellite imagery and calculated microbial contribution to snowmelt on an icefield of 1,900 km 2 . The red-snow area extended over about 700 km 2 , and in this area we determined that microbial communities were responsible for 17% of the total snowmelt there. Our results support hypotheses that snow-dwelling microbes increase glacier melt directly in a bio-geophysical feedback by lowering albedo and indirectly by exposing low-albedo glacier ice. Radiative forcing due to perennial populations of microbes may match that of non-living particulates at high latitudes. Their contribution to climate warming is likely to grow with increased melt and nutrient input.G lacier ablation is sensitive to changes in albedo 1 , with atmospheric 2,3 , hydrological 4 and ecological 5,6 consequences. Fresh snow reflects >90% of visible radiation, but during melt its grain size and water content increase, reducing albedo and further increasing snowmelt 1 . Impurities, including black carbon 3 , dust 4 , and resident microbes [7][8][9][10][11][12][13][14][15][16][17][18][19] , also lower albedo; however, microbes differ from non-living particulates in several critical ways. Perennial populations of photosynthetic microbes actively resurface following overwinter burial by snow 20 , and depend on liquid water and nutrients for survival and reproduction 13,14,[20][21][22] . This requirement for liquid water in a frozen environment imposes a selective force favouring a physiology that increases melt proximal to cell walls. The generation of meltwater through microbes' albedoreducing properties motivates an hypothesis of bio-geophysical feedback on glacial landscapes 13,16 , such as the Greenland ice sheet. This feedback hypothesis, whereby microbes increase because they produce needed meltwater, is an active research area [13][14][15][16][17][18][19] , yet field experiments testing its assumptions are absent.Glacier microbiomes are water-limited 21,22 , because ice is generally not metabolically available, and oligotrophic, because their nutrient content equals that of precipitation plus deposition by airborne dust, pollen, and so on, with only limited N-fixation by local cyanobacteria 21,22 . Moreover, rapidly percolating water through large-grained snow may exacerbate both water-and nutrient limitation for algae in supraglacial...

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supporting

confidence: 72%

mentioning

confidence: 99%

The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

et al. 2017

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“…Similar results were obtained from the Arctic (ratio of 34.1:1 for dark-red cysts; Mu¨ller et al, 1998) and Rocky Mountains, USA (ratio of 20.76:1 for C. nivalis; Bidigare et al, 1993). However, some minor peaks in our HPLC separation had an additional absorption shoulder at 375 nm when compared to the spectra for the astaxanthin calibration standard.…”

supporting

confidence: 72%

“…The esterification of astaxanthin with fatty acids, which was highly expressed in our C. nivalis samples, is regarded as a mechanism for efficient pigment concentration in cytoplasmic globules (Bidigare et al, 1993). The ultrastructure of our samples shows that massive globular structures fill a considerable part of the cell, with the plastid mainly centrally located.…”

mentioning

confidence: 90%

“…The older literature describes such algae as the 'haematochrom' (Kol, 1968;Ettl et al, 1983;Czygan, 1968Czygan, , 1970. More recent studies (Bidigare et al, 1993;Mu¨ller et al, 1998;Hoham & Duval, 2001 and references therein) have shown that the cells mainly form oxycarotenoids, in particular astaxanthin, and traces of canthaxanthin and echinenone.…”

Section: Introductionmentioning

confidence: 99%

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Photosynthesis, pigments and ultrastructure of the alpine snow algaChlamydomonas nivalis

Remias

Lütz‐Meindl

Lütz

2005

European Journal of Phycology

222

189

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Snow algae inhabit most of the cold regions worldwide, where long-lasting snow fields are common. The ecophysiology of snow algae has been studied intensively in North America and occasionally in polar regions. In the European Alps, the systematics of snow algae have been studied mainly by light microscopy. We studied temperature and light-dependence of photosynthesis, and plastid and extraplastid red pigment composition of red snow algae (Chlamydomonas nivalis) from snow patches in the high Alps of Austria. Both photosynthetic and respiratory data support the cryophilic adaptation of snow algal cells, but C. nivalis produced oxygen without any inhibition at temperatures up to 208C and maintained this for 1 h, at irradiances up to 1800 mmol m À2 s À1. Chlorophyll and primary carotenoid pigment composition was similar to that found in most other Chlorophyta. Additionally, large amounts of free and esterified astaxanthin were located in cytoplasmic lipid globules. Light and electron microscopy showed that the cell walls were frequently covered with tightly bound inorganic particles. Occasionally fungus-or bacteria-like structures were attached to the wall. The typical adult cell contained a single central chloroplast. Cytoplasmic structures were often difficult to resolve optically, as densely packed peripheral lipid globules, containing secondary carotenoids, occupied most of the cell volume. These pigments may shield the chloroplast from high irradiation (thus reducing the risk of photoinhibition) and may also be a potential carbon source during unfavourable climate conditions or the formation of daughter cells.

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