Annual patterns in algal pigment distribution in Arctic second year ice during the MOSAiC expedition 2019/2020

Algal pigment concentrations were retrieved from samples from second-year (SYI) ice, during the whole MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) in 2019 to 2020. During MOSAiC, RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. Sea ice data were collected starting with the onset of the study, at 85 degrees north and 137 degrees east, following the drift towards the Fram Strait, and returning into the marginal ice zone during the 4th leg of the expedition. Ice cores were collected at the various coring sites together with teams ICE and BGC (Nicolaus et al. 2022), to study the development of pigment patterns over time, on 3 specific ice-locations. Altogether, 277 samples have been collected and analysed. Ice cores were sliced in sections of 5-10 cm before analyses. Each of the sections was melted at room temperature after additions of filtered ambient seawater, under dark conditions. After extraction in 90 % acetone, samples were analysed using high-performance liquid chromatography (HPLC) on a Waters system (AWI). Algal pigments contain a multiple set of information. Firstly, pigment concentrations can show the presence of algal biomass in the various domains sampled. Secondly, marker pigments can reveal seasonal and temporal dynamics in algal community structure, by discerning specific algal classes like diatoms, cryptophytes, haptophytes and chlorophytes that have specific roles in biogeochemical cycles. Thirdly, certain pigments are indicative of the (photo)-physiological state of micro-algae and fourth, degradation products of the main chlorophyll a pigment further give an indication about senescence and grazing in the various habitats.

本数据集的藻类色素浓度数据采自2019至2020年北极气候研究多学科漂流观测站（Multidisciplinary drifting Observatory for the Study of Arctic Climate, MOSAiC）全科考周期内的二年生海冰（second-year ice, SYI）样品。在MOSAiC科考期间，极星号科考船（RV Polarstern）锚定在一块浮冰上，以期全面揭示北极气候在完整年度周期内的变化规律。本研究自启动之初便开始收集海冰数据，采样初始点位为北纬85度、东经137度，随浮冰漂移向弗拉姆海峡移动，并在科考第4航段期间返回海冰边缘带区域。科考团队联合ICE与BGC课题组（Nicolaus等，2022）在多个取芯点位采集冰芯，以研究3个特定海冰区域内色素特征随时间的演化规律。本次研究共采集并分析了277份样品。分析前，冰芯被切割为5~10厘米的切段。在暗环境下向每份切段加入过滤后的原位海水后，于室温下进行融冰。采用90%丙酮进行色素萃取后，使用沃特世（Waters）平台（AWI）的高效液相色谱（high-performance liquid chromatography, HPLC）对样品进行分析。藻类色素蕴含多维度的科学信息：其一，色素浓度可反映各采样区域内藻类生物量的存在情况；其二，特征色素可通过区分不同藻类门类（如硅藻、隐藻、定鞭藻及绿藻）来揭示藻类群落结构的季节与时间动态，这些藻类在生物地球化学循环中发挥着特定作用；其三，部分色素可指示微藻的（光）生理状态；其四，主要叶绿素a（chlorophyll a）的降解产物可进一步反映各生境中的藻类衰老与牧食作用情况。