COMMSENV-25-0117B_Olsen_et_al_2026_dataset

This dataset contains data from Leg 2 of The Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) expedition in 2019/2020 led by the Alfred Wegener Institute, Bremerhaven, Germany. In the following is a summary of measured variables and corresponding analysis methods. A more detailed description of the study and methods is given in the published article. The study described in the article Focus on how organic matter trapped in the sea ice in the polar night is released during sea ice deformation Samples for identification and quantification of bacteria and protists were taken from sea ice and water column by using KOVACS Mark II ice corer, Niskin water sampling bottles, horizontal plankton net tow by net attached to a remotely operated vehicle (ROV) and suction pump on the ROV. Samples for light microscopy was fixed with 25% glutaraldehyde and 20% hexamethylenetetramine-buffered formaldehyde solution to a final concentration of 0.1% and 1% (vol/vol), respectively. Protist cells were settled in Utermöhl sedimentation chambers for 48 h before identification and quantification in an inverted light microscope. Samples for flow cytometry (FCM) were fixed with glutaraldehyde, frozen in liquid nitrogen and stored at -80 °C. Bacteria stained with the nucleic acid dye SYBR Green I were quantified in a FACS Calibur (Becton Dickinson, San Jose, Calif. USA) flow cytometer. Heterotrophic nanoflagellates stained with SYBR Green I (HNF) were quantified in an Attune® NxT, Acoustic Focusing Cytometer (Thermo Fisher Scientific). Biomass was calculated from equivalent spherical diameter (ESD) and a carbon conversion factor. Phytoplankton were quantified from autofluorescence in chlorophyll a. Chlorophyll a samples from sea ice and water was collected on GF/F filters before extraction in 90% acetone and measurement in a Turner 10AU fluorometer, before and after acidification for Chla and phaeopigments, respectively (Holm-Hansen and Riemann 1978). Bacterial production was measured by incorporation of tritium labeled leucine according to the method of Smith and Azam (1992). Samples for particulate organic carbon (POC) from sea ice was collected on preignited Whatman GF/F filters, packed in tin cups and POC was measured in an elemental analyzer (Flash 2000, Thermo Scientific, Milan, Italy) at the University of La Rochelle, France (Littoral, Environment and Societies Joint Research Unit stable isotope facility). Ridge temperature was monitored with deployed mass balance buoys and temperature of level sea ice was measured manually in ice cores. Bulk salinity was measured in melted ice cores with a salinometer, and data on temperature and salinity were used to calculate brine volume fraction (BVF) following the method in Cox and Weeks (1983).ReferencesCox, G. F. N. & Weeks, W. F. Equations for Determining the Gas and Brine Volumes in Sea-Ice Samples. J. Glaciol. 29, 306–316 (1983).Holm-Hansen, O. & Riemann, B. Chlorophyll a Determination: Improvements in Methodology. Oikos 30, 438 (1978).Smith, D.C., F. Azam. A simple, economical method for measuring bacterial protein synthesis rates in seawater using 3H-leucine. Mar. Microb. Foodwebs 6, 107–114 (1992).

本数据集包含由德国不来梅港阿尔弗雷德·魏格纳研究所（Alfred Wegener Institute）主导的2019/2020年北极气候多学科漂流观测站（Multidisciplinary drifting Observatory for the Study of the Arctic Climate, MOSAiC）考察航次第二航段的观测数据。下文为实测变量及对应分析方法的概要，该研究与方法的详细说明已发表于相关学术论文。
该论文的研究聚焦极夜期间海冰中捕获的有机质在海冰形变过程中的释放机制。研究人员使用KOVACS Mark II冰芯钻、尼斯金采水器、搭载于遥控水下机器人（remotely operated vehicle, ROV）的水平浮游生物拖网以及ROV上的抽吸泵，从海冰与水柱中采集了用于细菌和原生生物鉴定与定量的样品。
用于光学显微镜检测的样品采用25%戊二醛与20%六亚甲基四胺缓冲甲醛溶液固定，最终浓度分别为0.1%与1%（体积比）。原生生物细胞在Utermöhl沉降室中沉降48小时后，通过倒置光学显微镜完成鉴定与定量。
流式细胞术（flow cytometry, FCM）样品经戊二醛固定后，置于液氮中冷冻，并于-80℃环境下保存。使用核酸染料SYBR Green I染色的细菌，通过FACS Calibur流式细胞仪（美国加利福尼亚州圣何塞市，Becton Dickinson公司）完成定量。经SYBR Green I染色的异养纳米鞭毛虫（Heterotrophic nanoflagellates, HNF）则在Attune® NxT声学聚焦流式细胞仪（赛默飞世尔科技公司）中完成定量。
生物量通过等效球径（equivalent spherical diameter, ESD）与碳转换系数计算得到。浮游植物通过叶绿素a的自发荧光完成定量。海冰与水体中的叶绿素a样品经GF/F滤膜收集后，用90%丙酮进行萃取，随后使用Turner 10AU荧光光度计分别在酸化前后测定叶绿素a与脱镁叶绿素的含量（参照Holm-Hansen与Riemann 1978年的方法）。
细菌生产力通过氚标记亮氨酸的掺入量测定，方法参照Smith与Azam（1992年）。海冰中的颗粒有机碳（particulate organic carbon, POC）样品经预灼烧的Whatman GF/F滤膜收集，封装于锡杯中，随后在法国拉罗谢尔大学（滨海环境与社会联合研究单元稳定同位素实验室）的元素分析仪（Flash 2000，赛默飞世尔科技，意大利米兰）中完成POC含量测定。
海冰脊温度通过部署的质量平衡浮标进行监测，平整海冰的温度则通过冰芯手动测量。熔冰冰芯的整体盐度使用盐度计测定，结合温度与盐度数据，参照Cox与Weeks（1983年）的方法计算盐水体积分数（brine volume fraction, BVF）。
参考文献：
1. Cox, G. F. N. & Weeks, W. F. 海冰样品中气体与盐水体积的测定方程. 《冰川学杂志》（Journal of Glaciology）, 29, 306–316 (1983).
2. Holm-Hansen, O. & Riemann, B. 叶绿素a测定：方法改进. 《Oikos》, 30, 438 (1978).
3. Smith, D. C. & Azam, F. 一种利用3H-亮氨酸测定海水中细菌蛋白质合成速率的简便经济型方法. 《海洋微生物食物网》（Marine Microbial Foodwebs）, 6, 107–114 (1992).