Key Laboratory of Polar Ecosystem and Climate Change, Ministry of Education; and School of Oceanography, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030, China.
Key Laboratory of Polar Ecosystem and Climate Change, Ministry of Education; and School of Oceanography, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030, China; Key Laboratory for Polar Science, Polar Research Institute of China, Ministry of Natural Resources, Shanghai 200136, China.
Sci Total Environ. 2024 Nov 15;951:175757. doi: 10.1016/j.scitotenv.2024.175757. Epub 2024 Aug 28.
Arctic fjords are hotspots of marine carbon burial, with diatoms playing an essential role in the biological carbon pump. Under the background of global warming, the proportion of diatoms in total phytoplankton communities has been declining in many high-latitude fjords due to increased turbidity and oligotrophication resulting from glacier melting. However, due to the habitat heterogeneity among Svalbard fjords, diatom responses to glacier melting are also expected to be complex, which will further lead to changes in the biological carbon pumping and carbon sequestration. To address the complexity, three short sediment cores were collected from three contrasting fjords in Svalbard (Krossfjorden, Kongsfjorden, Gronfjorden), recording the history of fjord changes in recent decades during significant glacier melting. The amino acid molecular indicators in cores K4 and KF1 suggested similar organic matter degradation states between these two sites. In contrast to the turbid Kongsfjorden and Gronfjorden, preserved fucoxanthin in Krossfjorden indicated a continuous increase in diatoms since the mid-1980s, corresponding to a 59 % increase in biological carbon pumping, as quantified by the δC of sedimentary organic carbon. The increasing biological carbon pumping in Krossfjorden is further attributed to its hard rock types in the glacier basin, compared to Kongsfjorden and Gronfjorden, which are instead covered by soft rocks, as confirmed by a one-dimensional model. Given the distribution of rock types among basins in Svalbard, we extrapolate our findings and propose that approximately one-fifth of Svalbard's fjords, especially those with hard rock basins and persistent marine-terminated glaciers, still have the potential for an increase in diatom fractions and efficient biological carbon pumping. Our findings reveal the complexity of fjord phytoplankton responses and biological carbon pumping to increasing glacier melting, and underscore the necessity of modifying Arctic marine carbon feedback to climate change based on results from fjords underlain by hard rocks.
北极峡湾是海洋碳埋藏的热点地区，硅藻在生物碳泵中起着至关重要的作用。在全球变暖的背景下，由于冰川融化导致的浊度增加和贫营养化，许多高纬度峡湾中硅藻在总浮游植物群落中的比例一直在下降。然而，由于斯瓦尔巴群岛峡湾之间的栖息地异质性，硅藻对冰川融化的反应也预计会很复杂，这将进一步导致生物碳泵和碳封存的变化。为了解决这种复杂性，从斯瓦尔巴群岛的三个不同峡湾（克罗斯峡湾、康斯峡湾、格陵兰峡湾）采集了三个短的沉积岩芯，记录了近几十年来冰川大量融化期间峡湾变化的历史。岩芯 K4 和 KF1 中的氨基酸分子指标表明这两个地点的有机物质降解状态相似。与浑浊的康斯峡湾和格陵兰峡湾不同，克罗斯峡湾中保存完好的岩藻黄素表明，自 20 世纪 80 年代中期以来，硅藻数量持续增加，生物碳泵的增加量为 59%，这是通过对沉积有机碳的δC 进行量化得出的。与康斯峡湾和格陵兰峡湾不同，克罗斯峡湾的生物碳泵的增加归因于其冰川盆地中的硬岩类型，而康斯峡湾和格陵兰峡湾的冰川盆地则覆盖着软岩，这一点得到了一维模型的证实。鉴于斯瓦尔巴群岛各盆地之间的岩石类型分布，我们推断我们的发现，并提出斯瓦尔巴群岛大约有五分之一的峡湾，特别是那些拥有硬岩盆地和持久的海洋终止冰川的峡湾，仍然有增加硅藻分数和有效生物碳泵的潜力。我们的研究结果揭示了峡湾浮游植物对冰川融化的反应和生物碳泵的复杂性，并强调了根据硬岩下的峡湾的结果来修改北极海洋碳对气候变化的反馈的必要性。
