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.

原绿球藻属是微小的（直径 1-2 微米）自养蓝藻，是世界上数量最多的光合物种。它们普遍存在于构成大片公海的亚热带和热带海洋环流中。由于它们的丰富度和分布，它们是许多海洋系统中的关键生物，并负责大部分初级生产力和养分循环，影响全球气候，是许多海洋生态系统的基础。原绿球藻直到最近才为科学所知，1998 年 Penny Chisholm（麻省理工学院）发现它彻底改变了我们对海洋光合作用的理解。由于这一相对较新的发现，我们对公海中天然原绿球藻种群的生物地球化学功能和生态作用只有初步的了解。当水柱高度分层时，原绿球藻细胞占主导地位，这种情况在马尾藻海（北大西洋亚热带）的百慕大地区夏季季节性发生。在这种高度分层的水域中，在阳光照射区（透光层）的底部和营养线的顶部有一个高叶绿素的特征层。该层被称为深层叶绿素最大值，以原绿球藻属为主。在热带和亚热带水域。分子和生理学研究已经确定了两种原绿球藻生态型，称为“高光”和“低光”生态型。低光生态型主导着低层优光带，而高光生态型主导着高光带，但不仅限于该区域。该提案旨在确定这种季节性积累的原因以及两种生态类型的垂直分布，从而有助于确定这种数量优势物种的生态作用。铁是光合细胞的基本需求，铁的分布和浓度在海洋系统中通常稀疏且较低，已被证明会显着影响浮游植物的分布和群落组成。最近，人们发现夏季马尾藻海百慕大地区出现了地下铁浓度最低值，该最低值与 DCM 和弱光原绿球藻生态型的积累同时发生。事实证明，即使表面铁浓度仍然很高，这种情况也会发生。该提案的目的是确定低铁浓度是否是决定原绿球藻细胞弱光生态型丰度的主要因素，这些细胞在夏季马尾藻海百慕大地区在数量上占主导地位。这将通过参加 R/V Atlantic Explorer 在马尾藻海百慕大地区的多次巡航来实现，这些巡航的时间与地下铁矿的早期、中期和晚期开发阶段一致和原绿球藻细胞的积累。在这些航行期间，将进行水柱剖面测量，以将原绿球藻生态型分布和生理学与可用铁浓度相关联。甲板上的孵化实验将在受控的光照和温度条件下进行，并将铁人工添加到从 DCM 和地表水中采集的水样中（在与铁剖面相同的位置采样）。然后将监测群落产生的反应，以检测浮游植物对添加铁的反应，并确定哪些物种（如果有）对添加做出反应。表层浮游植物群落和DCM的不同反应将决定系统的限制因素。在夏季和两个季节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: http://dx.10.1016/j.dsr2.2010.01.008
• 发表时间: 2010
• 期刊: Topical Studies in Oceanography
• 作者: Painter S

Biogeography of Cyanobacterial isiA Genes and Their Link to Iron Availability in the Ocean.

蓝藻 isiA 基因的生物地理学及其与海洋中铁可用性的联系。

• DOI: http://dx.10.3389/fmicb.2019.00650
• 发表时间: 2019
• 期刊: Frontiers in microbiology
• 作者: Li Q

Biogeography of photosynthetic light-harvesting genes in marine phytoplankton.

海洋浮游植物光合光捕获基因的生物地理学。

• DOI: http://dx.10.1371/journal.pone.0004601
• 发表时间: 2009
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Bibby TS

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

马尾藻海表层水中溶解钴的控制：与铁和铝的比较

• DOI: 10.1029/2011gb004155
• 发表时间: 2012-06-01
• 期刊: Global Biogeochemical Cycles
• 影响因子: 5.2
• 作者: R. Shelley;P. Sedwick;T. Bibby;Patricia Cabedo;T. Church;Rodney J. Johnson;Anna I. Macey;C. Marsay;E. Sholkovitz;S. Ussher;P. Worsfold;M. Lohan
• 通讯作者: M. Lohan