title: Small scale vertical gradients of Arctic ice algal  photophysiological properties.
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 (rETR(max)), photosynthetic efficiency (alpha), 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 alpha (0.098-0.130 (micromol photons m(-2)s(-1))(-1)) in December. F(v)/F(m) and alpha increased in March and May (0.468-0.588 and 0.141-0.438 (micromol photons m(-2)s(-1))(-1), respectively) indicating increased photosynthetic activity. In addition, increases in rETR(max) (3.3-16.4 a.u.) and E(k) (20-88 micromol 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).
authors.affiliation: School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775-7220, USA.
authors.forename: Sarah Story
authors.initials: SS
authors.lastname: Manes
authors.forename: Rolf
authors.initials: R
authors.lastname: Gradinger
mesh_terms: D000222:Adaptation, Physiological; D001110:Arctic Regions; D017377:Diatoms / Q000378:metabolism; D004579:Electron Transport; D056890:Eukaryota / Q000502:physiology*; D005843:Geography; D007053:Ice; D007287:Inorganic Chemicals / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D010860:Pigments, Biological / Q000378:metabolism; D012621:Seasons
chemical_list: D007053:Ice; D007287:Inorganic Chemicals; D010860:Pigments, Biological