Microbial communities in southern Victoria Land streams (Antarctica) I. Photosynthesis |
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Authors: | Clive Howard-Williams Warwick F Vincent |
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Institution: | (1) Taupo Research Laboratory, DSIR, P.O. Box 415, Taupo, New Zealand |
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Abstract: | The glacier-fed ephemeral streams of southern Victoria Land (ca. 78° S, 64° E) are colonised by an epilithon dominated by cyanobacterial mats and films. Biomass levels are often high (> 15 µg Chl a · cm–2). The mat structure, pigment and photosynthetic characteristics of these communities have been investigated on site. The mats in high light environments have a layered structure with high levels of light shielding accessory pigments in the upper layers and elevated chlorophyll a and phycocyanin concentrations in the lower layers. Photosynthetic rates per unit area (0.4–3.5 µg C · cm– 2 · hr–1) fall within the range reported for temperate communities. P vs I curves were used to separate high, intermediate and low light communities. Ik values for high light communities were at or lower than PAR recorded at midnight in the polar midsummer (ca 100 µ E m–2 · s–1). We did not detect photoinhibitory responses at the midday light intensities. In situ continuous nutrient enrichment experiments failed to demonstrate N or P limitation to pigment content or photosynthetic rates. We suggest that the growth of these communities is controlled by factors other than light and nutrients. |
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Keywords: | Antarctica biofilms cyanobacteria photosynthesis chlorophyll pigments nitrogen phosphorus epilithic algae |
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