Kongsfjorden is a small Arctic fjord but with great hydrographic complexity and has changed greatly due to the climate change. Arctic warming has increased melts of sea ice and glaciers that results in higher freshwater content. Microbial community variability and increasing terrestrial input were detected continuously in recent years ITag eukaryotic 18S rRNA V4 metabarcoding, photosynthetic pigments analysis and epifluorescence microscopy were used to reveal the dominant species of small eukaryotic community (<20 μm). Both Spearman correlation and redundant analysis were used to study the correlation between the small eukaryotes and the environmental conditions. In the present study, the surface water with salinity lower than 34 was thicker than in summers of previous years. The freshwater mixotrophic chrysophyte Poterioochromonas malhamensis was found for the first time as the dominant species. No general trends were found for the contributions of P. malhamensis to the total reads of small eukaryotes in water depths; and no obvious differences were found at different stations and water masses. Phagotrophy, which is more common than phototrophy at all times in P. malhamensis, is thought to be the main reason for the prevalence of P. malhamensis in Kongsfjorden. The occurrence of P. malhamensis induced a disorder in the small eukaryotic community, which biodiversity and composition showed weak correlation with the water masses. The dominance of the freshwater-originating phytoplankton may indicate an ecosystem change in the Kongsjforden, which probably might become more remarkable in the future as the climate continues to change.

中文翻译：

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淡水金藻 Poterioochromonas malhamensis 在北极海洋生态系统中的发生

Kongsfjorden 是一个很小的北极峡湾，但具有很大的水文复杂性，并且由于气候变化而发生了很大的变化。北极变暖增加了海冰和冰川的融化，导致淡水含量增加。近年来，微生物群落变异性和陆地输入不断增加，ITag真核18S rRNA V4元条形码，光合色素分析和荧光显微镜被用来揭示小型真核生物群落（<20μm）的优势物种。Spearman相关性和冗余分析都用于研究小型真核生物与环境条件之间的相关性。在本研究中，盐度低于 34 的地表水比往年夏季更浓。淡水混养金藻Poterioochromonas malhamensis 首次被发现为优势种。没有发现P. malhamensis对水深处小型真核生物总读数的贡献的一般趋势；不同站点、不同水体未发现明显差异。在P. malhamensis 中，吞噬一直比光营养更常见，被认为是P. malhamensis在Kongsfjorden流行的主要原因。P. malhamensis的发生导致小型真核生物群落紊乱，其生物多样性和组成与水团呈弱相关性。源自淡水的浮游植物的主导地位可能表明 Kongsjforden 的生态系统发生了变化，随着气候的持续变化，这种变化在未来可能会变得更加显着。