Mechanisms and effects of benthic biogeochemical iron cycling in glaciated fjords

冰川峡湾底栖生物地球化学铁循环的机制和影响

• 批准号: 490822598
• 负责人: Dr. Katja Laufer-Meiser
• 金额: --
• 依托单位: Forschungseinheit Marine Geosysteme
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/490822598?language=en
• 关键词: Mechanisms; effects; benthic; biogeochemical; iron

Glaciers are, along with rivers, hydrothermal vents and aeolian dust, known to be an important source of Fe, an essential but often limiting element for live in the ocean. However, up to 95 % of glacial Fe settles to fjord sediments close to the glacial source. It is currently not understood what the fate of glacial Fe is once it is exported to fjord sediments, i.e. if it is buried in these sediments or recycled and/or remobilized and released into the bottom water again. The biogeochemical cycle of Fe is driven by a complex interplay of biotic and abiotic reactions, connecting the Fe cycle to many other element cycles. Our understanding of how biogeochemical Fe cycling in glaciated fjords affects the fate of closely connected nutrients, such as Si, P or Mn, is also limited. Polar regions and especially fjord ecosystems are experiencing the most pronounced effects of climate change. However, only few studies so far link these effects to sedimentary biogeochemical cycles in fjords, so the actual effects on biogeochemical cycles, e.g. the Fe cycle, are largely unknown.In my previous work, I could show that Svalbard fjord sediments are important active interfaces between land and ocean, converting glacial Fe into potentially bioavailable Fe through benthic cycling. However, I also found that glacial retreat has the potential to change the biogeochemistry of fjord sediments, including the benthic Fe cycle, and decreases the potential of fjord sediments to be sources of potentially bioavailable Fe. The main aims of the proposed project are to identify the processes (biotic and abiotic) transforming glacially sourced Fe in fjord sediments, to quantify the effects of this conversion on the fate of Fe, Si, P and Mn, and to assess potential consequences of glacial retreat. This will be done by studying in detail the geochemistry, Fe-mineralogy and microbiology, as well as by measuring fluxes of Fe and connected nutrients in transects of Svalbard fjords with sea- and land-terminating glaciers (Kongsfjorden and Dicksonfjorden, respectively). A further aim of this project will be to elucidate the geographic distribution and relevance of benthic Fe-transformations in glaciated fjords. Therefore, I will investigate benthic Fe cycling in two more Svalbard fjords, the adjacent continental shelf as well as fjords in East Greenland and South Georgia. I will work together with colleagues focusing on pelagic (Fe) biogeochemistry, geochemists, microbiologists, paleooceanographers and modelers, all working on different aspects of Fe biogeochemistry. Such that our work will complement each other and we will be able to gain a detailed understanding of the amount and characteristics of glacial Fe, as well as transport and transformation pathways in the sediment and water column. The results will facilitate a better understanding of the transfer of glacially-derived nutrients from the cryosphere to the ocean and an assessment of potential consequences of climate change.

冰川与河流、热液喷口和风尘一起被认为是铁的重要来源，铁是海洋生物必需但往往是限制性的元素。然而，高达 95% 的冰川铁沉积在靠近冰川源头的峡湾沉积物中。目前尚不清楚冰川铁一旦被输出到峡湾沉积物中，即是否被埋在这些沉积物中或被回收和/或重新流动并再次释放到海底水中，其命运会如何。铁的生物地球化学循环是由生物和非生物反应的复杂相互作用驱动的，将铁循环与许多其他元素循环联系起来。我们对冰川峡湾中的生物地球化学铁循环如何影响密切相关的营养物（例如硅、磷或锰）的命运的了解也很有限。极地地区，尤其是峡湾生态系统正在经历气候变化最明显的影响。然而，迄今为止，只有很少的研究将这些影响与峡湾的沉积生物地球化学循环联系起来，因此对生物地球化学循环的实际影响，例如在我之前的工作中，我可以证明斯瓦尔巴峡湾沉积物是陆地和海洋之间重要的活跃界面，通过底栖循环将冰川铁转化为潜在的生物可利用铁。然而，我还发现冰川退缩有可能改变峡湾沉积物的生物地球化学，包括底栖铁循环，并降低峡湾沉积物作为潜在生物可利用铁来源的潜力。该项目的主要目的是确定峡湾沉积物中冰川来源铁的转化过程（生物和非生物），量化这种转化对铁、硅、磷和锰命运的影响，并评估冰川退缩的潜在后果。这将通过详细研究地球化学、铁矿物学和微生物学，以及测量斯瓦尔巴群岛横断面与海洋和陆地终止冰川（分别是孔斯峡湾和迪克森峡湾）的铁通量和相关营养物质来完成。该项目的进一步目标是阐明冰川峡湾中底栖铁转化的地理分布和相关性。因此，我将研究另外两个斯瓦尔巴群岛峡湾、邻近的大陆架以及东格陵兰岛和南乔治亚岛的峡湾的底栖铁循环。我将与专注于中上层（铁）生物地球化学的同事、地球化学家、微生物学家、古海洋学家和建模师一起工作，他们都致力于铁生物地球化学的不同方面。这样我们的工作将相互补充，我们将能够详细了解冰川铁的含量和特征，以及沉积物和水体中的运输和转化途径。研究结果将有助于更好地了解冰川产生的营养物质从冰冻圈向海洋的转移，并评估气候变化的潜在后果。