南极罗斯海–阿蒙森海2019—2020年夏季表层悬浮颗粒有机质组成及其控制因素

陆架边缘海悬浮颗粒有机质的组成及其来源研究是海洋物质生物地球化学循环研究的重要组成部分。南极的地理位置和气候环境特殊，其边缘海海洋环境受海–气–冰系统共同作用与影响，颗粒有机质的组成及来源具有独特的区域特征与全球意义，其控制因素研究对全面认识罗斯海、阿蒙森海等典型西南极边缘海生物地球化学循环以及生物泵传输效率具有重要的意义。利用中国第36次南极科学考察期间在西南极罗斯海–阿蒙森海区采集的59个表层海水悬浮颗粒物样品的有机碳、氮及其同位素和多种来源特异性的生物标志物分析测试数据，研究了罗斯海–阿蒙森海区域悬浮颗粒物中有机质的物质组成和分布特征，探讨了悬浮颗粒物中不同来源有机质含量与分布的控制因素，评估了不同有机地球化学指标在海–气–冰系统作用下的南极边缘海颗粒有机质组成及来源示踪的应用潜力。研究结果表明，罗斯海–阿蒙森海区海水表层颗粒物中颗粒有机碳（POC）的丰度与表层水体荧光值、海水pCO2、海洋浮游植物源和动物源生物标志物等的丰度分布趋势一致，这种水平分布趋势的一致性表明夏季罗斯海–阿蒙森海海水表层POC主要由浮游植物和动物现场产生。表层悬浮颗粒物总有机质C/N比普遍低于4，显示海区颗粒有机质受微生物降解改造作用明显；表层悬浮颗粒物δ13C值普遍低于−25.2‰，空间分布复杂，反映了南极冰架边缘海独特的贫13C的浮游植物源、富13C的动物源和贫13C的陆源颗粒有机组成的混合信号。表层悬浮颗粒物类脂生物标志物指标是区分不同来源POC组分的有效指标；菜籽甾醇、甲藻甾醇等浮游植物源生物标志物含量之和能较好地反映浮游植物源POC的贡献：近岸冰间湖区呈现高值，其浓度的空间变化受控于水体浮游植物活动；胆甾醇能较好地反映动物源POC的贡献：冰架边缘近岸区呈现高值，其浓度的空间变化受控于海区次级生产力水平和企鹅、海豹等生物量水平；长链的烷基类脂生物标志物较好地反映了南极岩性陆源POC的贡献，其浓度的空间变化受控于南极冰川作用主导的海陆相互作用的过程影响，往往在融冰过程明显的冰架边缘近岸区呈现高值。以上研究结果表明，生物标志物分子指标结合总有机质指标的多参数综合评估为准确辨识南极边缘海复杂的POC来源组成提供了有效的方法，在极区现代海洋（生物地球化学）过程及古海洋环境演化研究中具有广阔的应用空间。

Composition of organic materials and the control factors of suspended particulates in the surface water of the Ross Sea-Amundsen Sea in marginal sea of the southwestern Antarctic in austral summer 2019-2020

The study on the composition and source of suspended particulate organic matter in the marginal sea helps understand marine material biogeochemical cycle. The geographical location and climate environment of Antarctica are special. Antarctic marginal seas are affected by the interaction among marine, atmospheric, and glacial systems. The composition and source of particulate organic carbon (POC) has unique regional characteristics and global significance. Based on the dataset of organic carbon, nitrogen, and their isotopes and source-specific biomarkers extracted from 59 samples of suspended particulate matter collected from surface seawater in the western Antarctic marginal seas during the 36th Antarctic scientific expedition of China, the distribution and composition of organic matter in the suspended particulate matter were studied. The factors controlling the spatial distribution of particulate organic matter were examined, and the application potential of different organic geochemical proxies as the composition and source indicators to particulate organic matter in the Ross Sea-Amundsen Sea was evaluated. Results show that POC concentration in the surface water of the Ross Sea-Amundsen Sea is consistent with the spatial distribution of surface water fluorescence, seawater pCO2, and marine phytoplankton or animal derived biomarkers, which implies that POC in the surface water of Ross Sea-Amundsen Sea in summer is mainly produced by marine phytoplanktons and animals. The C/N ratio is generally below 4, indicating that POC in these regions is obviously degraded by microorganisms. The bulk δ13C value is generally lower than −25.2‰, and the spatial distribution is complex, which reflects the unique mixed POC signals of 13C-depleted phytoplankton source, 13C-enriched animal source , and 13C-depleted terrestrial origins from the Antarctic landscape. Lipid biomarker proxies archived from surface suspended particulate matter is an effective tool to distinguish sources of POC. The concentrations of phytoplankton-derived biomarkers such as brassicasterol and dinosterol reflect the contribution of phytoplankton-derived POC. The nearshore polynya shows a high value, and the spatial variability of its concentration is controlled by the phytoplankton activity in water column. Cholesterol reflects the contribution of animal derived POC. The nearshore at edge of ice shelf shows a high value, and the spatial variability of its concentration is controlled by the secondary productivity in water column and the biomass of penguins and seals. Long chain alkyl lipid biomarkers represent the contribution of lithologic POC from the Antarctic continental region. The spatial variation of their concentration is controlled by glacial activities, and often shows high values in the nearshore area at the edge of ice shelf where obvious ice melting is taken place. This research shows that the comprehensive evaluation of biomarker molecular indicators combined with bulk organic matter indicators provides an effective method for accurately resolving the complex POC matrix in the Antarctic marginal sea.