Small scale vertical gradients of Arctic ice algal photophysiological properties |
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Authors: | Sarah Story Manes Rolf Gradinger |
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Institution: | (1) School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775-7220, USA; |
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Abstract: | Photosynthetic parameters of phytoplankton and sea ice algae from landfast sea ice of the Chukchi Sea off Point Barrow, Alaska,
were assessed in spring 2005 and winter through spring 2006 using Pulse Amplitude Modulated (PAM) fluorometry including estimates
of maximum quantum efficiency (F
v/F
m), maximum relative electron transport rate (rETRmax), photosynthetic efficiency (α), and the photoadaptive index (E
k). The use of centrifuged brine samples allowed to document vertical gradients in ice algal acclimation with 5 cm vertical
resolution for the first time. Bottom ice algae (0–5 cm from ice–water interface) expressed low F
v/F
m (0.331–0.426) and low α (0.098–0.130 (μmol photons m−2s−1)−1) in December. F
v/F
m and α increased in March and May (0.468–0.588 and 0.141–0.438 (μmol photons m−2s−1)−1, respectively) indicating increased photosynthetic activity. In addition, increases in rETRmax (3.3–16.4 a.u.) and E
k (20–88 μmol photons m−2 s−1) from December to May illustrates a higher potential for primary productivity as communities become better acclimated to
under-ice light conditions. In conclusion, photosynthetic performance by ice algae (as assessed by PAM fluorometry) was tightly
linked to sea ice salinity, temperature, and inorganic nutrient concentrations (mainly nitrogen). |
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Keywords: | |
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