Effect of light, CO2 and nutrient limitation on photosynthesis in marine diazotrophic cyanobacteria.

光、二氧化碳和养分限制对海洋固氮蓝藻光合作用的影响。

• 批准号: NE/F003579/1
• 负责人: Eric Achterberg
• 金额: $ 13.8万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF003579%2F1
• 关键词: Effect; light; CO2; nutrient; limitation

The ocean plays a central role in the global carbon cycle. Uptake of carbon dioxide by the oceans has reduced the increase in atmospheric carbon dioxide that has arisen from fossil fuel burning and deforestation. It has long been know that the ocean biota play a major role in sequestering carbon dioxide on very long time scales (>1000 years). Recent evidence also suggests that the ocean biota play an important role on shorter time scales (10-100 years) as well. The balance between phytoplankton photosynthesis and community respiration determines the ability of the oceans to take up carbon dioxide. Nitrogen is generally considered to be the nutrient that limits phytoplankton photosynthesis. But what limits the amount of N in the ocean? Unlike most phytoplankton, which are N-limited, nitrogen fixing cyanobacteria have an unlimited supply of N. This is the N2 gas that is dissolved in seawater. Nitrogen-fixing cyanobacteria play a significant role in ocean nutrient and biogeochemical cycles as they are a major source of N, providing N for up to 50% of primary productivity in the most nutrient impoverished regions of the ocean. Nitrogen fixation is a key process that modulates the ability of the oceans to sequester carbon dioxide on time scales of 10 to 10,000 years. Limitation of nitrogen fixation results in lowered N availability for other primary producers reducing the potential of oligotrophic oceans to sequester carbon. This brings us to the issue of 'What limits the amount of nitrogen fixation in the ocean?' Amongst the environmental factors that may limit nitrogen fixation are temperature, light, carbon dioxide concentration and P- or Fe-limitation. It is argued that whereas N is the proximate limiting nutrient for phytoplankton photosynthesis in the sea, the ultimate limiting nutrient is either P (or Fe) because this nutrient limits the amount of nitrogen fixation. This proposal will examine the effects of light, carbon dioxide, P-limitation and Fe-limitation on photosynthetic properties and nitrogen fixation of nitrogen-fixing cyanobacteria. Research will be conducted under defined culture conditions in two species. One of these species, Trichodesmium, is documented to be of global significance. In addition, nitrogen fixation by unicellular cyanobacteria has recently been recognized to be significant. Therefore, the second species is one of these unicellular nitrogen fixers, Crocosphaera. The outcomes of this study will provide new insights into the mechanisms by which phosphorous and iron limit photosynthesis and nitrogen fixation in cyanobacteria. It will also provide new insights into the interaction with environmental factors such as light and carbon dioxide. This research will ultimately assist with several aspects of oceanographic studies on nutrient cycling and modeling the future importance of the oceans as C sinks.

海洋在全球碳循环中起着核心作用。海洋对二氧化碳的吸收减少了大气二氧化碳的增加，这是由于化石燃料燃烧和森林砍伐而引起的。长期以来，人们已经知道，海洋生物群在很长的尺度上（> 1000年）隔离二氧化碳。最近的证据还表明，海洋生物群在较短的时间尺度（10 - 100年）也起着重要作用。浮游植物光合作用与社区呼吸之间的平衡决定了海洋占二氧化碳的能力。氮通常被认为是限制浮游植物光合作用的营养。但是，是什么限制了海洋中N的数量？与大多数是二限的浮游植物不同的是，氮固定蓝细菌具有无限的N。这是溶解在海水中的N2气体。固氮蓝细菌在海洋营养和生物地球化学周期中起着重要作用，因为它们是N的主要来源，在最营养贫困的海洋地区，最多可占用原发性生产力的50％。氮固定是一个关键过程，可调节海洋以10到10，000年的时间尺度隔离二氧化碳的能力。氮固定的局限性导致其他主要生产者降低了氮的可用性，从而降低了贫营养海洋隔离碳的潜力。这使我们陷入了“什么限制了海洋中的氮固定量？”的问题。在可能限制氮固定的环境因素中，温度，光，二氧化碳浓度和p-或fe限制。有人认为，尽管N是海洋中浮游植物光合作用的近端限制营养素，但最终的限制营养素是P（或Fe），因为这种营养素限制了氮固定量。该建议将研究光，二氧化碳，p限制和Fe限制对光合特性和氮固定氰基菌菌的影响。研究将在两个物种的定义培养条件下进行。这些物种之一，即trichodesmium，被证明具有全球意义。此外，最近已经认为，单细胞蓝细菌固定氮是显着的。因此，第二种是这些单细胞氮固定剂Crocosphaera之一。这项研究的结果将为蓝细菌中磷和铁限制光合作用和氮固定的机制提供新的见解。它还将为与环境因素（如光和二氧化碳）的相互作用提供新的见解。这项研究最终将有助于进行有关营养循环的海洋学研究的几个方面，并建模海洋作为C下沉的未来重要性。