ABSTRACT: Ice algae are key contributors to primary production and carbon fixation in the Arctic, and light availability is assumed to limit their growth and productivity. We investigated photo-physiological responses in sea ice algae to increased irradiance during a spring bloom in West Greenland. During a 14 d field experiment, light transmittance through sea ice was manipulated to provide 3 under-ice irradiance regimes: low (0.04), medium (0.08), and high (0.16) transmittances. Chlorophyll a decreased with elevated light availability relative to the control. Maximum dark-adapted photosynthetic efficiency (Φ_{PSII_max}) showed an initially healthy and productive ice algae community (Φ_{PSII_max} > 0.6), with Φ_{PSII_max} decreasing markedly under high-light treatments. This was accompanied by a decrease in the light utilization coefficient (α) and photosynthetic capacity (maximum relative electron transfer rate), and a decrease in the ratio of mono- to polyunsaturated fatty acids. This was partly explained by a corresponding increase of photoprotective pigments (diadinoxanthin and diatoxanthin), and a development of mycosporine-like amino acids as identified from a distinctive spectral absorption peak at 360 nm. After 14 d, in situ fluorescence imaging revealed significant differences in Φ_{PSII_max} between treatments of dark-adapted cells (i.e. those sampled before sunrise and after sunset), during diel cycles, with clear chronic photoinhibition in high and medium treatments. Data demonstrate the high sensitivity of spring-blooming Arctic sea ice algae to elevated irradiance caused by loss of snow cover. The predicted loss of snow cover on landfast ice will negatively impact ice algae, their potential primary production, and nutritional quality for higher trophic levels.

中文翻译：

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辐照度增加对北极海冰藻生物量，光生物学，营养质量和色素组成的影响

摘要：冰藻是北极初级生产和固碳的主要贡献者，人们认为光的可用性会限制其生长和生产力。我们调查了西格陵兰岛春季开花期间海冰藻类对光辐射增加的光生理反应。在14天的野外实验中，操纵了通过海冰的透光率以提供3种冰下辐照度制度：低（0.04），中（0.08）和高（0.16）透射率。相对于对照，叶绿素a随着光利用率的提高而降低。最大的黑暗适应光合作用效率（_{ΦPSII_max}）显示出最初健康且高产的冰藻群落（_{ΦPSII_max} > 0.6），其中_{ΦPSII_max}在高光下明显减少。这伴随着光利用率（α）和光合能力（最大相对电子传递速率）的降低，以及单不饱和脂肪酸与多不饱和脂肪酸之比的降低。从360nm的独特光谱吸收峰可以看出，这部分地由光保护性颜料（二恶黄质和重黄质）的相应增加以及霉菌素样氨基酸的发展而解释。14 d后，原位荧光成像显示_{ΦPSII_max有}显着差异在暗适应的细胞处理之间（即日出之前和日落之后采样的细胞），diel周期之间，在高和中度处理中具有明显的慢性光抑制作用。数据表明，春季盛开的北极海冰藻对由于积雪的丧失而引起的辐照度升高具有很高的敏感性。预计陆地冰上积雪的减少将对冰藻，其潜在的初级生产以及营养水平较高的海藻产生不利影响。