Lund-Hansen Lars Chresten, Jensen Lasse Z, Sorrell Brian, Andersen Per, Meire Lorenz, Søgaard Dorte Haubjerg, Santl-Temkiv Tina
Arctic Research Centre, Department of Biology, Aarhus University, Aarhus, Denmark.
CIFAR Research Centre, Department of Biology, Aarhus University, Aarhus, Denmark.
Sci Rep. 2025 Aug 13;15(1):29660. doi: 10.1038/s41598-025-15516-5.
Open water leads in the sea ice covering the Polar regions are becoming more frequent and cover larger areas as a result of the warming and thinning of the ice. Refreezing of the leads advances the occurrence of young and newly formed sea ice (nilas), which has a thickness of < 10 cm and is characterized by a highly saline surface brine. Due to the growth of fragile frost flowers exposed at its surface, nilas can become a significant source of bromine, mercury, sea salt aerosols, bioaerosols, and ice nucleating particles for the atmosphere. Here we report the results of a study where we investigated the initial formation phase of a 3-6 mm-thick nilas in cleared sea ice ponds. Samples for quantifications of macronutrients, microorganisms, Chlorophyll a (Chl a) and photobiology were collected from seawater, nilas, and brine 5 and 24 h, after the experiment commenced. The concentration changes between constituents were scaled relative to changes in salinity with the enrichment index (I). Nilas was enriched in microalgae and Chl a and the brine was highly enriched in bacteria, virus like particles (VLPs) and algae after only 5 h. We did not find a significant further enrichment between 5 and 24 h of nilas formation. This indicates that the initial formation phase of the nilas is an important step in distributing nutrients and microorganisms in nilas and brine. Only particulate matter was enriched in nilas and brine and none of the macronutrients. Photosynthetic microalgae were strongly impaired in the nilas and the brine, where no fluorescence signal could be detected supposedly due to a combination of excessive light at the surface and high brine salinity. The reasons for the observed differences in enrichments are evaluated and discussed including concentration of particulate matter, evaporation of surface brine, microbial growth and concentration of microorganisms in the sea surface microlayer (SML). Further studies are needed to decipher which of the proposed mechanisms were predominantly responsible for the observed enrichments as well as how these enrichments affect firstly the frost flowers and secondly the atmosphere.
由于极地地区海冰的融化和变薄，覆盖在极地地区的海冰中的开阔水道变得更加频繁，覆盖面积也更大。水道的重新冻结促进了年轻的新形成海冰（尼罗冰）的出现，尼罗冰厚度小于10厘米，其特点是表面盐水盐分很高。由于其表面暴露的脆弱霜花的生长，尼罗冰可能成为大气中溴、汞、海盐气溶胶、生物气溶胶和冰核颗粒的重要来源。在此，我们报告一项研究结果，该研究调查了在清理后的海冰池塘中3-6毫米厚尼罗冰的初始形成阶段。在实验开始后5小时和24小时，从海水、尼罗冰和盐水中采集了用于定量大量营养素、微生物、叶绿素a（Chl a）和光生物学的样本。各成分之间的浓度变化通过富集指数（I）相对于盐度变化进行缩放。仅5小时后，尼罗冰中微藻和Chl a就有所富集，而盐水中细菌、病毒样颗粒（VLP）和藻类高度富集。在尼罗冰形成的5至24小时之间，我们未发现有显著的进一步富集现象。这表明尼罗冰的初始形成阶段是在尼罗冰和盐水中分配营养物质和微生物的重要步骤。只有颗粒物在尼罗冰和盐水中有所富集，而大量营养素均未富集。光合微藻在尼罗冰和盐水中受到严重损害，由于表面光线过强和盐水盐度高的综合作用，在那里无法检测到荧光信号。对观察到的富集差异的原因进行了评估和讨论，包括颗粒物浓度、表面盐水蒸发、微生物生长以及海表面微层（SML）中微生物的浓度。需要进一步研究来解读所提出的哪些机制主要导致了观察到的富集现象，以及这些富集现象如何首先影响霜花，其次影响大气。
