Surface gas-exchange processes of snow algae

Abstract

The red-colored chlorophyte Chlamydomonas nivalis is commonly found in summer snowfields. We used a modified Li-Cor gas-exchange system to investigate surface gas-exchange characteristics of snow colonized by this alga, finding rates of CO2 uptake up to 0.3 μmol m−2⋅s−1 in dense algal blooms. Experiments varying the irradiance resulted in light curves that resembled those of the leaves of higher plants. Red light was more effective than white and much more effective than green or blue, because of the red astaxanthin that surrounds and masks the algal chloroplasts. Integrating daily course measurements of gas exchange showed CO2 uptake around 2,300 μmol⋅m−2⋅day−1 in heavily colonized patches, indicating that summer snowfields can be surprisingly productive

Photosynthesis, pigments and ultrastructure of the alpine snow algaChlamydomonas nivalis

“…Only the younger cells from Ku¨htai, which still contained green parts of the chloroplast, not shaded by astaxanthin, indicated that some light dissipation took place (AZ/VAZ ¼ 0.27). Similar results relating to the light-dependence of photosynthesis in red snow algae was reported by Williams et al (2003) for North America. Rae et al (2000) described photosynthesis in Antarctic phytoplankton as temperature-dependent and showed similar kinetics to the data in Fig.…”

“…Earlier studies used different methods ( 14 C incubation or CO 2 gas exchange) and, with one exception (a study of a few green snow species in the former Czechoslovakia, Koma´rek et al, 1973), were carried out on algae from other continents, such as North America (Thomas, 1972;Mosser et al, 1977;Thomas & Duval, 1995;Williams et al, 2003).…”

“…This was discussed as a novel adaptation strategy. Williams et al (2003) described CO 2 fixation at snow temperatures of 1-38C in a snow patch. They assumed that photosynthesis was related to the red snow covering the patch.…”

“…Williams et al (2003) claim that, world-wide, snow algae might play an important role in balancing the atmospheric carbon budget.…”

Recent climate extremes alter alpine lake ecosystems

“…For axis 1, the absolute value of climate variable scores exceeded 0.75 for all but FDSP, MSPK, and SFRD, which were the highest scoring variables for axis 2. that increases in the nonchromophoric fraction led to elevated DOC concentrations because light absorbance by lake water decreased and Secchi depth increased despite the elevated DOC concentrations. Possible sources of nonchromophoric DOC include in-lake algal and bacterial production (27), higher DOC inputs from more persistent snowfield microbial communities in years with longer snow seasons (28,29), and inputs of nonchromophoric DOC of allochthonous origin. Our observations of increasing DOC concentrations in lake water during mid-late summer periods in the 2000s, when the inflows of several lakes ceased to flow, support an interpretation that autochthonous production of nonchromophoric DOC by the plankton was important.…”