Macroalgae such as kelp are important ecosystem engineers in the Polar Regions and potentially affected by freshening and ocean warming. The endemic Arctic kelp Laminaria solidungula might be particularly imperiled and become locally extinct from Arctic fjord systems in the future, since temperature increase is most pronounced in the Polar Regions. Additionally, increased temperatures cause glacier and sea ice melting and enhancing terrestrial run-off from snowfields, which eventually can result in hyposaline conditions in fjord systems. We conducted a multiple-stressor experiment at four temperatures (0, 5, 10, 15 °C) and two salinities (SA 25, 35) to investigate the combined effects of increasing temperature and decreasing salinities on the physiological and biochemical status of young L. solidungula sporophytes. Both drivers had significant and interacting impacts, either in an additive or antagonistic way, dependent on the respective response variable. The maximum quantum yield of photosystem II (Fv/Fm) significantly declined with temperature increase and low salinity. Even though the absolute pigment content was not affected, the deepoxydation state of the xanthophyll cycle increased with intensified stress. Higher temperatures affected the C:N ratio significantly, mainly due to reduced nitrogen uptake, while SA 25 supported the nitrogen uptake, resulting in an attenuation of the effect. The concentration of mannitol decreased at SA 25. At control SA 35 mannitol level remained steady between 0 and 10 °C but significantly decreased at 15 °C. Conclusively, our results show that L. solidungula is very susceptible to both drivers of climate change, especially when they are combined. Implications to species ecology are discussed.

中文翻译：

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温度和盐度联合胁迫对地方性北极褐海藻 Laminaria solidungula J. Agardh 的影响

海带等大型藻类是极地地区重要的生态系统工程师，可能会受到清新和海洋变暖的影响。地方性北极海带 Laminaria solidungula 可能特别危险，并在未来从北极峡湾系统局部灭绝，因为极地地区的温度升高最为明显。此外，温度升高会导致冰川和海冰融化，并增加雪地的陆地径流，最终可能导致峡湾系统的低盐度条件。我们在四种温度 (0, 5, 10, 15 °C) 和两种盐度 (SA 25, 35) 下进行了多压力源实验，以研究升高温度和降低盐度对幼鱼生理生化状态的综合影响。 .solidungula 孢子体。取决于各自的响应变量，两个驱动因素都具有显着且相互作用的影响，无论是以加性还是对抗性的方式。光系统 II 的最大量子产率 (Fv/Fm) 随温度升高和盐度降低而显着下降。即使绝对色素含量没有受到影响，叶黄素循环的深度氧化状态随着压力的增加而增加。较高的温度显着影响 C:N 比，主要是由于氮吸收减少，而 SA 25 支持氮吸收，导致效果减弱。甘露醇的浓度在 SA 25 时降低。在对照 SA 35 下，甘露醇水平在 0 和 10 °C 之间保持稳定，但在 15 °C 时显着降低。最后，我们的结果表明 L. solidungula 非常容易受到气候变化的两种驱动因素的影响，尤其是当它们结合在一起时。讨论了对物种生态学的影响。