The Arctic is seasonally exposed to long periods of low temperatures and complete darkness. Consequently, perennial primary producers have to apply strategies to maximize energy efficiency. Global warming is occurring in the Arctic faster than the rest of the globe. The highest amplitude of temperature rise occurs during Polar Night. To determine the stress resistance of the ecosystem-engineering kelp Laminaria digitata against Arctic winter warming, non-meristematic discs of adult sporophytes from Porsangerfjorden (Finnmark, Norway) were kept in total darkness at 0°C and 5°C over a period of three months. Physiological variables, namely maximum quantum yield of photosynthesis (Fv/Fm) and dry weight, as well as underlying biochemical variables including pigments, storage carbohydrates, total carbon and total nitrogen were monitored throughout the experiment. Although all samples remained in generally good condition with Fv/Fm values above 0.6, L. digitata performed better at 0°C than at 5°C. Depletion of metabolic products resulted in a constant decrease of dry weight over time. A strong decrease in mannitol and laminarin was observed, with greater reductions at 5°C than at 0°C. However, the total carbon content did not change, indicating that the sporophytes were not suffering from “starvation stress” during the long period of darkness. A decline was also observed in the accessory pigments and the pool of xanthophyll cycle pigments, particularly at 5°C. Our results indicate that L. digitata has a more active metabolism, but a lower physiological and biochemical performance at higher temperatures in the Arctic winter. Obviously, L. digitata is well adapted to Arctic Polar Night conditions, regardless of having its distributional center at lower latitudes. Despite a reduced vitality at higher temperatures, a serious decline in Arctic populations of L. digitata due to winter warming is not expected for the near future.

中文翻译：

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气候变化对海带的影响 Laminaria digitata – 模拟北极冬季变暖


北极季节性地暴露在长时间的低温和完全黑暗的环境中。因此，常年初级生产者必须采用策略来最大限度地提高能源效率。北极的全球变暖速度比全球其他地区快。气温上升的最高幅度发生在极夜期间。为了确定生态系统工程海带 Laminaria digitata 对北极冬季变暖的抗逆性，来自 Porsangerfjorden（挪威芬马克）的成年孢子体的非分生孢子体的非分生孢子盘在 0°C 和 5°C 的完全黑暗中保持了三个月。在整个实验过程中监测生理变量，即光合作用的最大量子产率 （Fv/Fm） 和干重，以及潜在的生化变量，包括色素、储存碳水化合物、总碳和总氮。尽管所有样品总体上保持良好状态，Fv/Fm 值高于 0.6，但 L. digitata 在 0°C 下的表现优于 5°C。 代谢产物的耗竭导致干重随着时间的推移不断下降。观察到甘露醇和海带多糖的强烈减少，5°C 时的减少幅度大于 0°C 时的减少幅度。 然而，总碳含量没有变化，表明孢子体在长时间的黑暗中没有遭受“饥饿应激”。在辅助色素和叶黄素循环色素库中也观察到下降，尤其是在 5°C 时。 我们的结果表明，L. digitata 的新陈代谢更活跃，但在北极冬季的较高温度下生理生化性能较低。显然，栉桔 （L. digitata） 很好地适应了北极极夜条件，无论其分布中心是否位于低纬度地区。 尽管在高温下活力会降低，但预计在不久的将来，由于冬季变暖，北极 L. digitata 种群不会严重下降。