The impact of iron availability on the ecology of Prochlorococcus populations in the Sargasso Sea

铁的可用性对马尾藻海原绿球藻种群生态的影响

• 批准号: NE/E009670/1
• 负责人: Thomas Bibby
• 金额: $ 4.24万
• 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: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE009670%2F1
• 关键词: impact; iron; availability; ecology; Prochlorococcus

Prochlorococcus spp. are tiny (1-2 um diameter) autotrophic cyanobacteria and are the most numerically dominant photosynthetic species in the world. They are ubiquitous in the subtropical and tropical ocean gyres that comprise vast areas of the open ocean. Due to their abundance and distribution, they are key organisms in many marine systems, and are responsible for a large proportion of gross primary productivity and nutrient cycling, which affect the global climate and are the basis of many marine ecosystems. Prochlorococcus was unknown to science until recently, when its discovery by Penny Chisholm (MIT) in 1998 revolutionised our understanding of marine photosynthesis. As a result of this relatively recent discovery, we have only a rudimentary understanding of the biogeochemical functions and ecological roles of natural Prochlorococcus populations in the open ocean. Prochlorococcus cells dominate when the water column is highly stratified, a situation that occurs seasonally in the summer in the Bermuda region of the Sargasso Sea (subtropical North Atlantic). In such highly stratified waters, there is a characteristic layer of high chlorophyll at the base of the sunlit zone (euphotic layer) and the top of the nutracline. This layer, termed the deep chlorophyll maximum, is dominated by Prochlorococcus spp. in tropical and subtropical waters. Molecular and physiological studies have identified two Prochlorococcus ecotypes, known as 'high-light' and 'low-light' ecotypes. The low-light ecotypes dominate the lower euphotic zone, whereas the high-light ecotypes dominate the upper euphotic zone, but are not exclusively restricted to this region. This proposal aims to determine the reason for this seasonal accumulation and the vertical distribution of the two ecotypes, and so help to define the ecological role of this numerically dominant species. Iron is a fundamental requirement for photosynthetic cells and iron distributions and concentrations, which are often sparse and low in oceanic systems, have been shown to significantly affect phytoplankton distribution and community composition. Recently, a sub-surface minimum in iron concentration has been found to develop at the Bermuda region of the Sargasso Sea in the summer, and this minimum is co-incident with both the DCM and the accumulation of the low-light Prochlorococcus ecotype. This situation has been shown to develop even when iron concentrations at the surface remain high. The objective of this proposal is to determine whether a low iron concentration is the main factor in determining the abundance of the low-light ecotype of Prochlorococcus cells that are numerically dominant in the Bermuda region of the Sargasso Sea in the summer. This will be achieved by participation in a number of cruises aboard the R/V Atlantic Explorer in the Bermuda region of the Sargasso Sea, which are timed to coincide with the early, mid and late stages of development of both the sub-surface iron minimum and the accumulation of Prochlorococcus cells. During these cruises, water-column profile measurements will be made to correlate Prochlorococcus ecotype distribution and physiology with available iron concentration. On-deck incubation experiments will be performed under controlled light and temperature conditions, and iron will be artificially added to water samples taken from the DCM and the surface water (sampled at the same location as iron profiles). The resulting response of the community will then be monitored to detect a response of the phytoplankton to added iron, and to identify which if any species respond to the addition. The different responses of phytoplankton communities at the surface and DCM will determine the limiting factors of the system. Conducting similar experiments during the summer and over two seasons will confirm the temporal development of these features.

ProChorococcus spp。是微小的（1-2 um）自养蓝细菌，是世界上数值最主的光合物种。它们在亚热带和热带海洋回旋中无处不在，包括开阔的海洋地区。由于它们的丰度和分布，它们是许多海洋系统中的关键生物，并且负责大部分的主要生产力和营养循环，这会影响全球气候，并且是许多海洋生态系统的基础。直到最近，Penny Chisholm（麻省理工学院）在1998年的发现彻底改变了我们对海洋光合作用的理解，直到最近，科学的氯环球菌才未知。由于这一相对较新的发现，我们只对天然prochorococcus种群在开阔的海洋中的生物地球化学功能和生态作用有基本的理解。当水柱高度分层时，占主导地位的细胞占主导地位，这种情况在夏季的萨尔加索海（亚热带北大西洋）的百慕大地区季节性发生。在如此高度分层的水域中，在阳光区（舒适层）和营养林的顶部有一个高叶绿素的特征层。该层被称为深叶绿素最大值，由甲氯环球菌属于叶绿素。在热带和亚热带水中。分子和生理研究已经鉴定出两种核酸型生态型，称为“高光”和“低光”生态型。低光的生态型主导着下部舒适区，而高光生态型主导着上舒适区，但不仅限于该区域。该提案旨在确定这种季节性积累和两种生态型的垂直分布的原因，因此有助于定义该数值主导物种的生态作用。铁是光合细胞，铁分布和浓度的基本要求，在海洋系统中通常稀疏且较低，已显示出显着影响浮游植物的分布和社区组成。最近，在夏季，在萨尔加索海的百慕大地区发现了铁浓度的最低地下表面，并且该最低限度与DCM和低光核球菌生态型的累积相关。即使表面的铁浓度保持较高，这种情况也会发展出来。该提案的目的是确定低铁浓度是否是确定夏季萨尔加索海百慕大地区占主导地位的氯环菌细胞低光生态型的主要因素。这将通过参加萨尔加索海百慕大地区的R/V大西洋探险家参加许多巡航，这与亚面铁最小值的早期，中期和晚期阶段相吻合。在这些巡航过程中，将进行水柱剖面测量，以将氯环球菌分布和生理学与可用的铁浓度相关联。甲板孵育实验将在受控的光和温度条件下进行，并将铁添加到从DCM和地表水中采集的水样中（与铁概况相同的位置采样）。然后，将监测社区的最终反应，以检测浮游植物的反应以增加铁，并确定是否有任何物种对添加作出反应。表面和DCM的浮游植物群落的不同反应将决定系统的限制因素。在夏季和两个季节中进行类似的实验将证实这些特征的时间发展。

项目成果

Summertime trends in pelagic biogeochemistry at the Porcupine Abyssal Plain study site in the northeast Atlantic

东北大西洋豪猪深海平原研究地点的中上层生物地球化学夏季趋势

• DOI: 10.1016/j.dsr2.2010.01.008
• 发表时间: 2010
• 期刊: Topical Studies in Oceanography
• 作者: Painter S

Biogeography of photosynthetic light-harvesting genes in marine phytoplankton.

• DOI: 10.1371/journal.pone.0004601
• 发表时间: 2009
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Bibby TS;Zhang Y;Chen M
• 通讯作者: Chen M

Controls on dissolved cobalt in surface waters of the Sargasso Sea: Comparisons with iron and aluminum

• DOI: 10.1029/2011gb004155
• 发表时间: 2012-06
• 期刊: Global Biogeochemical Cycles
• 影响因子: 5.2
• 作者: R. Shelley;P. Sedwick;T. Bibby;Patricia Cabedo-Sanz;T. Church;Rodney J. Johnson;Anna I. Macey;C. Marsay;E. Sholkovitz;S. Ussher;P. Worsfold;M. Lohan