Sea ice algae contribute up to 25% of the primary productivity of polar seas and seed large‐scale ice‐edge blooms. Fluctuations in temperature, salinity, and light associated with the freeze/thaw cycle can significantly impact the photophysiology of ice‐associated taxa. The effects of multiple co‐stressors (i.e., freezing temperature and high brine salinity or sudden high light exposure) on the photophysiology of ice algae were investigated in a series of ice tank experiments with the polar diatom Fragilariopsis cylindrus under different light intensities. When algal cells were frozen into the ice, the maximum quantum yield of photosystem II photochemistry (PSII; F_v/F_m) decreased possibly due to the damage of PSII reaction centers and/or high brine salinity stress suppressing the reduction capacity downstream of PSII. Expression of the rbcL gene was highly up‐regulated, suggesting that cells initiated strategies to enhance survival upon freezing in. Algae contained within the ice‐matrix displayed similar levels of F_v/F_m regardless of the light treatments. Upon melting out, cells were exposed to high light (800 μmol photons · m⁻² · s⁻¹), resulting in a rapid decline in F_v/F_m and significant up‐regulation of non‐photochemical quenching (NPQ). These results suggest that ice algae employed safety valves (i.e., NPQ) to maintain their photosynthetic capability during the sudden environmental changes. Our results infer that sea ice algae are highly adaptable when exposed to multiple co‐stressors and that their success can, in part, be explained by the ability to rapidly modify their photosynthetic competence – a key factor contributing to algal bloom formation in the polar seas.

中文翻译：

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冰藻光生理的冻结，融化和轻度应力：使用冰罐对冰藻硅藻Fragilariopsis cylindrus（Bacillariophyceae）进行非原位培养。

海冰藻类占极地海和大型冰缘种子繁殖的初级生产力的25％。与冻结/解冻周期相关的温度，盐度和光照的波动会显着影响与冰相关的分类单元的光生理。在极地硅藻Fragilariopsis cylindrus在不同光强度下进行的一系列冰罐实验中，研究了多个共同胁迫因素（即，冷冻温度和高盐度或突然的高光照）对冰藻光生理的影响。将藻类细胞冷冻到冰中后，光系统II光化学（PSII; F _v / F _m降低）可能是由于PSII反应中心的损坏和/或高盐度应力抑制了PSII下游的还原能力。所述的表达RBC被高度上调L基因，这表明启动战略，以提高当在冷冻存活的细胞。藻类含有冰基质内显示的相似水平˚F _v / ˚F_米不论光治疗。融解后，细胞暴露在高光下（800μmol光子·m ^-2  ·s ^-1），导致F _v / F _m迅速下降。以及非光化学猝灭（NPQ）的显着上调。这些结果表明，冰藻在突然的环境变化过程中使用了安全阀（即NPQ）来维持其光合作用能力。我们的结果表明，海冰藻类在暴露于多个共同胁迫时具有高度适应性，并且其成功可以部分地由迅速改变其光合能力的能力来解释，这是极地海藻华形成的关键因素。