THE SHORT-TERM EFFECT OF IRRADIANCE ON THE PHOTOSYNTHETIC PROPERTIES OF ANTARCTIC FAST-ICE MICROALGAL COMMUNITIES(1).

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Date
2009-12
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WILEY-BLACKWELL PUBLISHING, INC
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© 2009 Phycological Society of America
Abstract
Although sea-ice represents a harsh physicochemical environment with steep gradients in temperature, light, and salinity, diverse microbial communities are present within the ice matrix. We describe here the photosynthetic responses of sea-ice microalgae to varying irradiances. Rapid light curves (RLCs) were generated using pulse amplitude fluorometry and used to derive photosynthetic yield (ΦPSII ), photosynthetic efficiency (α), and the irradiance (Ek ) at which relative electron transport rate (rETR) saturates. Surface brine algae from near the surface and bottom-ice algae were exposed to a range of irradiances from 7 to 262 μmol photons · m(-2)  · s(-1) . In surface brine algae, ΦPSII and α remained constant at all irradiances, and rETRmax peaked at 151 μmol photons · m(-2)  · s(-1) , indicating these algae are well acclimated to the irradiances to which they are normally exposed. In contrast, ΦPSII , α, and rETRmax in bottom-ice algae reduced when exposed to irradiances >26 μmol photons · m(-2)  · s(-1) , indicating a high degree of shade acclimation. In addition, the previous light history had no significant effect on the photosynthetic capacity of bottom-ice algae whether cells were gradually exposed to target irradiances over a 12 h period or were exposed immediately (light shocked). These findings indicate that bottom-ice algae are photoinhibited in a dose-dependent manner, while surface brine algae tolerate higher irradiances. Our study shows that sea-ice algae are able to adjust to changes in irradiance rapidly, and this ability to acclimate may facilitate survival and subsequent long-term acclimation to the postmelt light regime of the Southern Ocean.
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Keywords
Science & Technology, Life Sciences & Biomedicine, Plant Sciences, Marine & Freshwater Biology, MARINE & FRESHWATER BIOLOGY, PLANT SCIENCES, Antarctic sea ice, E(k), PAM fluorometry, photoinhibition, rapid light curves, rETR(max), alpha, Theta(PSII), SEA-ICE, MCMURDO-SOUND, PRIMARY PRODUCTIVITY, ALGAL COMMUNITIES, PHOTOSYSTEM-II, D1 PROTEIN, PHOTOINHIBITION, PHOTOADAPTATION, PHOTOINACTIVATION, PHOTOPROTECTION
Citation
JOURNAL OF PHYCOLOGY, 2009, 45 (6), pp. 1290 - 1298 (9)
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