Sea ice algae, comprised mainly of diatoms, are the main primary producers in polar ecosystems, and they are generally distributed with the highest biomass at the bottom of ice. The taxonomy of ice algae has been traditionally investigated using light microscopy, but molecular techniques, including pigment analysis, have recently provided new insights into the diversity and physiology of ice algae. However, no comparative taxonomic survey has been conducted for ice algae thus far. Here, we investigated differences and similarities in (1) the diversity and (2) the photosynthetic strategies of diatom communities in sea ice and the underlying seawater of Saroma-Ko Lagoon, Hokkaido, Japan, using algal pigment signatures determined by ultra-high performance liquid chromatography, light and scanning electron microscopy and Ion Torrent next-generation sequencing techniques targeting the 18S rRNA gene (i.e., DNA barcoding). Ice algae typically possessed greater biomass (> 20-fold) and chlorophyll (Chl) a breakdown products than under-ice phytoplankton, suggesting that the ice algae formed blooms, and cell senescence and disruption could be significant mitigating factors. At the genus level, the diversity of diatoms in sea ice was higher than in under-ice seawater, although the evenness was comparable or lower in ice algae than in under-ice phytoplankton. Ice algae had a larger xanthophyll pool size and a higher ratio of photoprotective to photosynthetic pigments (11-fold and 4.5-fold higher, respectively) than under-ice phytoplankton. The results indicated that ice algae were well adapted to changes in the light regime, which could partly support their survival capability and high taxonomic diversity.

中文翻译：

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日本Saroma-Ko泻湖冰藻和冰下浮游植物的多样性和光保护能力差异：显微镜和DNA条形码的比较分类硅藻分析

海冰藻主要由硅藻组成，是极地生态系统的主要初级生产者，一般分布在冰底生物量最高。冰藻的分类学传统上使用光学显微镜进行研究，但分子技术，包括色素分析，最近为冰藻的多样性和生理学提供了新的见解。然而，迄今为止，尚未对冰藻进行比较分类调查。在这里，我们使用由超高性能确定的藻类色素特征，研究了（1）日本北海道 Saroma-Ko Lagoon 海冰和底层海水中硅藻群落的多样性和（2）光合作用策略的差异和相似之处液相色谱，光学和扫描电子显微镜以及靶向 18S rRNA 基因的 Ion Torrent 下一代测序技术（即 DNA 条形码）。与冰下浮游植物相比，冰藻通常具有更大的生物量（> 20 倍）和叶绿素 (Chl) 分解产物，这表明冰藻形成了大量繁殖，细胞衰老和破坏可能是重要的缓解因素。在属水平上，海冰中硅藻的多样性高于冰下海水，尽管冰藻的均匀度与冰下浮游植物相当或更低。与冰下浮游植物相比，冰藻具有更大的叶黄素池大小和更高的光保护色素与光合色素的比率（分别高 11 倍和 4.5 倍）。结果表明，冰藻很好地适应了光照条件的变化，