Department of Environment & Energy, Sejong University, Seoul 05006, South Korea.
Division of Polar Ocean Science Research, Korea Polar Research Institute (KOPRI), Incheon 21990, South Korea.
Sci Total Environ. 2018 Jun 15;627:802-811. doi: 10.1016/j.scitotenv.2018.01.251. Epub 2018 Feb 2.
Sea ice contains a large amount of dissolved organic matter (DOM), which can be released into the ocean once it melts. In this study, Arctic sea ice DOM was characterized for its optical (fluorescence) properties as well as the molecular sizes and composition via size exclusion chromatography and Fourier transformation ion cyclotron resonance mass spectrometry (FT-ICR MS). Ice cores were collected along with the underlying seawater samples in Cambridge Bay, an Arctic area experiencing seasonal ice formation. The ice core samples revealed a marked enrichment of dissolved organic carbon (DOC) compared to the seawater counterparts (up to 6.2 times greater). The accumulation can be attributed to in situ production by the autotrophic and heterotrophic communities. Fluorescence excitation emission matrices (EEMs) elaborated with parallel factor analysis (PARAFAC) evidenced the prevalence of protein-like substances in the ice cores, which likely results from in situ production followed by accumulation in the ice. Size exclusion chromatography further revealed the in situ production of all DOM size fractions, with the exception of the humic substance fraction. The majority of DOM in both the ice and seawater consists of low molecular weight compounds (<350 Da) probably derived by the microbial degradation/transformation of freshly produced DOM. Molecular characterization also supported the in situ production of DOM and highlighted the marked difference in molecular composition between sea ice and seawater. This study provides new insights into the possible role of sea ice DOM in the Arctic carbon cycle under climate change.
海冰中含有大量溶解有机物质（DOM），一旦融化就会释放到海洋中。在这项研究中，通过尺寸排阻色谱和傅里叶变换离子回旋共振质谱（FT-ICR MS）对北极海冰 DOM 的光学（荧光）特性以及分子大小和组成进行了表征。在剑桥湾（一个经历季节性冰形成的北极地区）采集了冰芯和底层海水样本。与海水样本相比，冰芯样本中的溶解有机碳（DOC）明显富集（高达 6.2 倍）。这种积累可归因于自养和异养群落的原位产生。运用平行因子分析（PARAFAC）的荧光激发发射矩阵（EEMs）详细说明了冰芯中存在大量的类蛋白物质，这可能是由于原位产生的物质在冰中积累所致。尺寸排阻色谱进一步揭示了除腐殖质以外的所有 DOM 大小分数的原位产生。冰和海水中的大部分 DOM 都由低分子量化合物组成（<350 Da），可能是由新产生的 DOM 的微生物降解/转化而来。分子特征分析也支持 DOM 的原位产生，并强调了海冰和海水之间分子组成的显著差异。本研究为气候变化下海冰 DOM 在北极碳循环中可能发挥的作用提供了新的见解。
