Snow cover on sea ice is the most important factor controlling light availability for sea ice algae, but it is predicted by climate models to become more variable and stochastic. Here, we document effects of a sudden, complete loss of the entire snow cover on first-year sea ice at Kangerlussuaq Fjord, West Greenland, due to a natural Föhn wind event that caused a ca. 17 °C air temperature increase over 36 h. We applied Imaging-PAM fluorometry to examine effects of snow cover on algal distribution and photobiology and observed a rapid decrease in algal biomass associated with loss of the skeletal ice crystal layer on the underside of the ice that had supported most of the visible algae. Furthermore, the remaining algae were photobiologically stressed, as seen in a significant decrease in the dark-acclimated fluorescence yield (Φ_{PSII_max}) from 0.55 before snow loss to 0.41 after. However, recovery in the dark suggested that non-photosynthetic quenching was successfully dissipating excess energy in the community and that there was little photodamage. An observed decrease in the photosynthetic efficiency α from 0.22 to 0.16 µmol é m⁻² s⁻¹ is therefore likely to be due to photoacclimation and the change in community composition. Centric diatoms and flagellates were the main taxa lost in the snow loss event, whereas the sea ice specialist Nitzschia frigida increased in numbers. These observations are similar to those seen in artificial snow-clearing experiments and consistent with snow clearing being a useful approach for investigating the complex interactions between snow cover, irradiance fluctuations, and ice algal performance.

中文翻译：

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西格陵兰峡湾康克鲁斯瓦克春季生长期间整个峡湾积雪迅速消失对冰藻的光生物学影响

海冰上的积雪是控制海冰藻光可用性的最重要因素，但气候模型预测它会变得更加可变和随机。在这里，我们记录了在西格陵兰岛康克鲁斯瓦克峡湾的第一年海冰上整个积雪突然完全消失的影响，这是由于自然的焚风事件导致了大约。17 °C 空气温度在 36 小时内升高。我们应用成像-PAM 荧光测定法来检查积雪对藻类分布和光生物学的影响，并观察到藻类生物量的快速减少与支持大部分可见藻类的冰下侧的骨骼冰晶层的损失有关。此外，剩余的藻类受到光生物胁迫，如暗适应荧光产量（Φ_{PSII_max} ) 从降雪前的 0.55 到降雪后的 0.41。然而，在黑暗中恢复表明非光合作用猝灭成功地消散了群落中的多余能量，并且几乎没有光损伤。因此，观察到的光合效率 α 从 0.22 降低到 0.16 µmol é m ^-2 s ^-1可能是由于光驯化和群落组成的变化。中心硅藻和鞭毛虫是雪崩事件中丢失的主要分类群，而海冰专家Nitzschia frigida数量增加。这些观察结果与人工除雪实验中的观察结果相似，并且与除雪是研究积雪、辐照度波动和冰藻性能之间复杂相互作用的有用方法一致。