Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment
Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment
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DOI：
10.5194/bg-9-1137-2012
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发表时间：
2012-01-01
期刊：
影响因子：
4.9
通讯作者：
Clarke, A.
中科院分区：
文献类型：
--
作者：
Henley, S. F.;Annett, A. L.;Clarke, A.
对颗粒有机碳（δ C-13（POC））中的稳定碳同位素特征以及海冰和地表水中相关生物地球化学参数进行高分辨率时间序列分析，可以深入了解影响南极半岛西部沿海海冰环境中δ C-13（POC）的因素。该研究涵盖了 2004 年至 2006 年间玛格丽特湾北部莱德湾的两个南方夏季。2005/2006 年夏季开花期间，硅藻物种组成发生转变，无刺长鼻藻几乎完全占据生物量优势，这与 delta C-13 (POC) 中约千分之十的负同位素变化密切相关，而这种变化无法用 CO2 浓度或同位素特征的同时变化来解释。我们假设 delta C-13(POC) 变化可能是由不同硅藻物种中不同的生化机制和碳浓缩机制 (CCM) 的利用驱动的。具体来说，P. inermis 中非常低的 delta C-13(POC) 可能是由于缺乏 CCM 造成的，而一些在较高 delta C-13(POC) 时丰富的硅藻物种可能会使用 CCM。这些短暂但明显的负δ C-13（POC）偏移导致季节性平均δ C-13（POC）信号减少千分之四，该信号被转移到沉积物圈闭和岩心顶部沉积物，因此有可能保存在沉积记录中。对比海冰条件和上层水柱分层的季节之间千分之四的差异与冰期-间冰期南大洋三角洲 C-13(POC) 变异性的全部幅度相匹配，因此，我们将浮游植物物种变化作为影响沉积三角洲 C-13(POC) 的潜在重要因素。我们还发现海冰中的 Delta C-13(POC) 显着高于地表水，这与半封闭环境中的自养碳固定一致，并且可能来自生产后降解、HCO3- 的生物利用和胞外聚合物的产生。这项研究证明了地表水硅藻形态效应和同位素重海冰衍生物质对南极沿海环境和底层沉积物中三角洲 C-13(POC) 的重要性，以及对基于硅藻的三角洲 C-13(POC) 在沉积记录中的利用的影响。
A high resolution time-series analysis of stable carbon isotopic signatures in particulate organic carbon (delta C-13(POC)) and associated biogeochemical parameters in sea ice and surface waters provides an insight into the factors affecting delta C-13(POC) in the coastal western Antarctic Peninsula sea ice environment. The study covers two austral summer seasons in Ryder Bay, northern Marguerite Bay between 2004 and 2006. A shift in diatom species composition during the 2005/06 summer bloom to near-complete biomass dominance of Proboscia inermis is strongly correlated with a large ~10 parts per thousand negative isotopic shift in delta C-13(POC) that cannot be explained by a concurrent change in concentration or isotopic signature of CO2. We hypothesise that the delta C-13(POC) shift may be driven by the contrasting biochemical mechanisms and utilisation of carbon-concentrating mechanisms (CCMs) in different diatom species. Specifically, very low delta C-13(POC) in P. inermis may be caused by the lack of a CCM, whilst some diatom species abundant at times of higher delta C-13(POC) may employ CCMs. These short-lived yet pronounced negative delta C-13(POC) excursions drive a 4 parts per thousand decrease in the seasonal average delta C-13(POC) signal, which is transferred to sediment traps and core-top sediments and consequently has the potential for preservation in the sedimentary record. This 4 parts per thousand difference between seasons of contrasting sea ice conditions and upper water column stratification matches the full amplitude of glacial-interglacial Southern Ocean delta C-13(POC) variability and, as such, we invoke phytoplankton species changes as a potentially important factor influencing sedimentary delta C-13(POC). We also find significantly higher delta C-13(POC) in sea ice than surface waters, consistent with autotrophic carbon fixation in a semi-closed environment and possible contributions from post-production degradation, biological utilisation of HCO3- and production of exopolymeric substances. This study demonstrates the importance of surface water diatom speciation effects and isotopically heavy sea ice-derived material for delta C-13(POC) in Antarctic coastal environments and underlying sediments, with consequences for the utility of diatom-based delta C-13(POC) in the sedimentary record.