Defining the Realized Niche of the Two Major Clades of Trichodesmium: A Study on the West Florida Shelf
Defining the Realized Niche of the Two Major Clades of Trichodesmium: A Study on the West Florida Shelf
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DOI：
10.3389/fmars.2022.821655
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发表时间：
2022-06
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通讯作者：
Kristina A. Confesor;C. Selden;K. E. Powell;Laura A. Donahue;T. Mellett;S. Caprara;A. Knapp;K. Buck;P. Chappell
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作者：
Kristina A. Confesor;C. Selden;K. E. Powell;Laura A. Donahue;T. Mellett;S. Caprara;A. Knapp;K. Buck;P. Chappell
蓝细菌Trichodesmium通过固定二氮（N2）缓解氮限制，在支持海洋生产力方面发挥着重要作用。两个常见的束毛藻分支：T. Astragraeum和T. thiebautii，都观察到在沃茨沿着西佛罗里达大陆架（WFS）。我们假设，这些类群占据不同的实现生态位，其中T。thiebautii是更海洋的分支。在跨越多个季节的三次独立的WFS考察（2015年，2018年和2019年）中收集了用于DNA和水化学分析的样品;通过定量PCR对来自两个进化枝的单拷贝管家基因rnpB的丰度进行了计数。我们进行了一系列的统计分析，以评估Trichodesmium分支丰度的物理化学数据的背景下。我们观察到一个一致的沿海与开放的海洋分离的两个分支：T。在溶解铁（dFe）和地下水示踪剂Ba浓度显著较高的浅水沃茨中发现了蓝绿藻，而在海水中发现了蓝绿藻。thiebautii丰度与水柱深度呈正相关。在2015年的环流入侵夹带密西西比河水带来了更高的dFe和升高的丰度的两个分支离岸的50米等深线，这表明这两个分支都受到铁的限制外架。然而，以前的工作已经观察到T. thiebautii比T.这是第一个研究Trichodesmium生态位分化在沿海环境中。了解这两个关键类群的环境生态位对它们对全球氮和碳循环的贡献以及它们对全球气候变化的响应具有重要意义。
The cyanobacterium Trichodesmium plays an essential role supporting ocean productivity by relieving nitrogen limitation via dinitrogen (N2) fixation. The two common Trichodesmium clades, T. erythraeum and T. thiebautii, are both observed in waters along the West Florida Shelf (WFS). We hypothesized that these taxa occupy distinct realized niches, where T. thiebautii is the more oceanic clade. Samples for DNA and water chemistry analyses were collected on three separate WFS expeditions (2015, 2018, and 2019) spanning multiple seasons; abundances of the single copy housekeeping gene rnpB from both clades were enumerated via quantitative PCR. We conducted a suite of statistical analyses to assess Trichodesmium clade abundances in the context of the physicochemical data. We observed a consistent coastal vs. open ocean separation of the two clades: T. erythraeum was found in shallow waters where the concentrations of dissolved iron (dFe) and the groundwater tracer Ba were significantly higher, while T. thiebautii abundance was positively correlated with water column depth. The Loop Current intrusion in 2015 with entrained Missisippi River water brought higher dFe and elevated abundance of both clades offshore of the 50 m isobath, suggesting that both clades are subject to Fe limitation on the outer shelf. Whereas, previous work has observed that T. thiebautii is more abundant than T. erythraeum in open ocean surface waters, this is the first study to examine Trichodesmium niche differentiation in a coastal environment. Understanding the environmental niches of these two key taxa bears important implications for their contributions to global nitrogen and carbon cycling and their response to global climate change.