The Trichodesmium consortium: the marine N-cycle at the microscale?

Trichodesmium 财团：微观尺度的海洋氮循环？

• 批准号: NE/K015095/1
• 负责人: Michael Wyman
• 金额: $ 15.78万
• 依托单位: University of Stirling
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK015095%2F1
• 关键词: Trichodesmium; consortium; marine; cycle; microscale

About half of all of the carbon fixed in photosynthesis on Earth takes place in the oceans. Most of this occurs in those regions which are far from land and which are usually quite poorly provided with the plant nutrients required to fuel growth. In the most desert-like regions found in the tropical and subtropical oceans, some bacteria use sunlight for photosynthesis in just same way as the plants on land and are also able to exploit the abundant nitrogen present in the overlying atmosphere. This nitrogen-fixing process not only supports the growth of these bacteria under these hostile, nutrient-poor conditions but also adds this additional source of nitrogen to the oceans that then acts a fertilizer for other marine life.The nitrogen-fixers are usually found in ocean regions where there is a deficit in the availability of other forms of nitrogen and so are at a particular advantage in these areas. The nitrogen deficit is due to other types of bacteria that remove nitrogen from the ocean in a process known as denitrification. Usually, these denitrifiers, as they are called, are only found to be active in deeper waters where the reduced availability of oxygen allows them to thrive under conditions where other life is usually quite sparse. We have found, though, that the denitrifiers and the nitrogen fixers seem to be able to live together nearer to the surface and, what is more, that they are both active in the cycling of nitrogen in the oceans.The research to be carried out in this proposal is focussed on firstly putting names to these denitrifiers, so that we can recognise where they are found in the oceans, and secondly, on trying to find out what these bacteria might be doing within this newly discovered association. This is important because the oceans help to drawdown carbon dioxide from the atmosphere and the rates at which they do so depend on how fertile they are. If the denitrifiers are removing large quantities of nitrogen from the surface waters then this will affect the overall productivity of the oceans. We rely on the microscopic plants found in the ocean to lock away some of the extra carbon dioxide that is released to the atmosphere by the burning of fossil fuels. If their vital nitrogen supply is reduced by denitrification then this unfixed carbon dioxide will be left in the atmosphere to contribute to future global warming.Another important facet of this research is that the powerful greenhouse gas nitrous oxide can be released in the denitrification process as well as being consumed. Not only does this gas warm the planet when it is vented to the atmosphere but it is also responsible for breaking down some of the ozone layer that filters out hazardous ultraviolet rays from the sun. We need to know also, therefore, what the likely scale of the impact of nitrous oxide cycling within this consortium of bacteria is and how it might be affected by future climate change.By improving our understanding of the scale of nitrogen inputs and losses that might occur in the newly discovered bacterial association we should be in a better informed position to assess how significant the partners in the consortium are in the larger scale global nitrogen cycle that influences the fertility of the land as well as the oceans.

地球上光合作用中固定的碳约有一半发生在海洋中。大多数这种情况发生在远离陆地的地区，这些地区通常缺乏促进生长所需的植物养分。在热带和亚热带海洋中发现的最像沙漠的地区，一些细菌利用阳光进行光合作用，就像陆地上的植物一样，并且还能够利用上层大气中丰富的氮。这种固氮过程不仅支持这些细菌在这些不利的、营养贫乏的条件下生长，而且还为海洋提供了额外的氮源，然后为其他海洋生物提供肥料。固氮剂通常发现于其他形式的氮缺乏的海洋区域，因此在这些区域具有特别的优势。氮缺乏是由于其他类型的细菌在一个称为反硝化的过程中从海洋中去除氮。通常情况下，这些被称为“浮游生物”的生物只在较深的沃茨中活跃，那里氧气的可用性降低，使它们能够在其他生物通常相当稀少的条件下茁壮成长。然而，我们已经发现，固氮菌和固氮菌似乎能够在更接近表面的地方生活在一起，而且，它们都活跃在海洋中的氮循环中。这项建议中进行的研究重点是首先给这些固氮菌命名，以便我们能够识别它们在海洋中的位置，其次，试图找出这些细菌在这个新发现的协会中可能做些什么。这一点很重要，因为海洋有助于减少大气中的二氧化碳，而海洋减少二氧化碳的速度取决于海洋的肥沃程度。如果浮游生物从表面沃茨中去除大量的氮，那么这将影响海洋的整体生产力。我们依靠在海洋中发现的微生物植物来锁定一些因燃烧化石燃料而释放到大气中的额外二氧化碳。如果它们的氮供应因反硝化作用而减少，那么这些未固定的二氧化碳将留在大气中，导致未来的全球变暖。这项研究的另一个重要方面是，强大的温室气体一氧化二氮可以在反硝化过程中释放，也可以被消耗。这种气体排放到大气层中不仅使地球变暖，而且还破坏了一些臭氧层，这些臭氧层过滤了来自太阳的有害紫外线。因此，我们还需要知道，通过提高我们对新发现的细菌群落中可能发生的氮输入和损失规模的理解，我们应该能够更好地了解该群落中的合作伙伴在更大范围内的重要性。影响土地和海洋肥力的全球氮循环规模。