H+ fluxes in phytoplankton - a mechanistic and modelling study of their physiological roles and impact upon community responses to ocean acidification

浮游植物中的 H 通量 - 其生理作用及其对海洋酸化群落反应影响的机制和模型研究

基本信息

批准号：
NE/J021296/1
负责人：
Glen Wheeler
金额：
$ 7.8万
依托单位：
Plymouth Marine Laboratory
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ021296%2F1
关键词：
H+fluxes phytoplankton mechanistic modelling

项目摘要

The oceans remove about half of the carbon dioxide (CO2) that we release into the atmosphere and produce about half of the oxygen that we breathe. The photosynthetic marine phytoplankton play a major role in these processes, contributing to global carbon, nitrogen and sulphur cycling. Phytoplankton are not simply single-celled plants. They represent an extremely diverse collection of algae with many novel traits and complex evolutionary histories which are still poorly understood. The increase in atmospheric carbon dioxide due to the burning of fossil fuels has major climatic implications. A result of the oceans absorbing much of this CO2 is the acidification of surface ocean waters - a drop from pH 8.2 to pH 7.7 is predicted by the end of the century. As ocean pH has remained stable for many millions of years this may have profound effects on many marine organisms that have not previously experienced this level of pH or rate of change during their recent evolutionary history. Ocean acidification will also change the levels of carbonate and nutrient ions, all of which may have significant impacts on the physiology of marine phytoplankton. While some of these impacts are being intensively studied, the direct effect of decreased pH itself on phytoplankton physiology has been largely overlooked. Marine phytoplankton, like all organisms, must tightly regulate their cellular pH by in order to maintain favourable conditions for cellular processes. We have been studying mechanisms of pH regulation in coccolithophores, an important group of phytoplankton that play a major role in the global carbon cycle through their production of calcium carbonate scales (coccoliths) which sink to the deep ocean following cell death. We have discovered that coccolithophores use protein pores (channels) in their outer cell membrane to regulate pH inside the cell. These channels allow H+ to exit from the cell whenever acidity in the cell increases, thus acting to keep pH inside the cell constant. This is particularly important for coccolithophores as the production of coccoliths in the cell results in a constant production of H+ which need to be removed or the acidity inside of the cell would increase to dangerous levels. This novel mechanism is extremely sensitive to changes in external pH and may no longer function effectively at near future ocean pH levels. We have also found this form of H+ channel in diatoms, the most numerous and productive group of phytoplankton. Remarkably, we have found that coccolithophore cells acclimated in the laboratory to growth at lower pH no longer appear to use a H+ channel. While this suggests coccolithophores may be able to cope with lower pH, we do not know the wider or long-term physiological implications of this mechanistic switch. This is clearly something we urgently need to understand. This project will examine in detail the mechanisms of pH homeostasis in coccolithophores and diatoms. Our modelling studies predict that mechanisms of cellular pH regulation are likely to differ in large and small phytoplankton species as these will experience greatly different fluctuations in pH at the cell surface due to physical effects of cell size on diffusion at the cell surface. We propose that different mechanisms of pH homeostasis employed by phytoplankton species may play a major role in the response of these organisms to ocean acidification. In order to gauge how these novel aspects of phytoplankton physiology will impact upon marine ecosystems on a broader scale, we will use modelling approaches to examine how cellular H+ fluxes in phytoplankton cells respond to changes in their environment. These mathematical models will enable us to predict the ranges of pH experienced by different phytoplankton species both currently and in the future and will allow us to evaluate their impact on the diversity of natural phytoplankton populations that will be studied in related programmes.

海洋吸收了我们释放到大气中约一半的二氧化碳 (CO2)，并产生了我们呼吸的约一半的氧气。光合海洋浮游植物在这些过程中发挥着重要作用，有助于全球碳、氮和硫循环。浮游植物不仅仅是单细胞植物。它们代表了极其多样化的藻类集合，具有许多新颖的特征和复杂的进化历史，而这些特征和复杂的进化历史仍然知之甚少。由于燃烧化石燃料而导致大气中二氧化碳的增加对气候产生重大影响。海洋吸收大量二氧化碳的结果是表层海水酸化——预计到本世纪末，pH 值将从 8.2 降至 7.7。由于海洋 pH 值数百万年来一直保持稳定，这可能会对许多海洋生物体产生深远的影响，这些生物体在最近的进化史上从未经历过这种 pH 值水平或变化率。海洋酸化还会改变碳酸盐和营养离子的水平，所有这些都可能对海洋浮游植物的生理产生重大影响。虽然其中一些影响正在得到深入研究，但 pH 值下降本身对浮游植物生理学的直接影响在很大程度上被忽视了。与所有生物体一样，海洋浮游植物必须严格调节其细胞 pH 值，以维持细胞过程的有利条件。我们一直在研究颗石藻的 pH 调节机制，颗石藻是一类重要的浮游植物，通过产生碳酸钙鳞片（颗石藻），在细胞死亡后沉入深海，在全球碳循环中发挥着重要作用。我们发现颗石藻利用其外细胞膜上的蛋白质孔（通道）来调节细胞内的 pH 值。当细胞内的酸度增加时，这些通道允许 H+ 从细胞中排出，从而保持细胞内的 pH 恒定。这对于颗石藻尤其重要，因为细胞中颗石藻的产生会导致 H+ 的持续产生，需要将其去除，否则细胞内的酸度会增加到危险水平。这种新颖的机制对外部 pH 值的变化极其敏感，在不久的将来海洋 pH 值水平下可能不再有效发挥作用。我们还在硅藻中发现了这种形式的 H+ 通道，硅藻是数量最多、生产力最高的浮游植物群。值得注意的是，我们发现在实验室中适应较低 pH 条件下生长的颗石藻细胞似乎不再使用 H+ 通道。虽然这表明颗石藻可能能够应对较低的 pH 值，但我们不知道这种机制转换的更广泛或长期的生理影响。这显然是我们迫切需要了解的。该项目将详细研究颗石藻和硅藻的 pH 稳态机制。我们的模型研究预测，大型和小型浮游植物物种的细胞 pH 调节机制可能有所不同，因为由于细胞大小对细胞表面扩散的物理影响，这些浮游植物的细胞表面 pH 值会经历截然不同的波动。我们认为浮游植物物种采用的不同 pH 稳态机制可能在这些生物体对海洋酸化的反应中发挥重要作用。为了衡量浮游植物生理学的这些新方面将如何在更广泛的范围内影响海洋生态系统，我们将使用建模方法来研究浮游植物细胞中的细胞 H+ 通量如何响应其环境的变化。这些数学模型将使我们能够预测不同浮游植物物种当前和未来所经历的 pH 范围，并使我们能够评估它们对相关计划中将研究的自然浮游植物种群多样性的影响。

项目成果

期刊论文数量（5）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Dynamic changes in carbonate chemistry in the microenvironment around single marine phytoplankton cells.

单个海洋浮游植物细胞周围微环境中碳酸盐化学的动态变化。

DOI：
http://dx.10.1038/s41467-017-02426-y
发表时间：
2018
期刊：
Nature communications
影响因子：
16.6
作者：
Chrachri A
通讯作者：
Chrachri A

The role of coccolithophore calcification in bioengineering their environment.

颗石藻钙化在其环境生物工程中的作用。

DOI：
http://dx.10.1098/rspb.2016.1099
发表时间：
2016
期刊：
Proceedings. Biological sciences
影响因子：
0
作者：
Flynn KJ
通讯作者：
Flynn KJ

The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing.

海洋微生物真核生物转录组测序项目（MMETSP）：通过转录组测序阐明海洋真核生物的功能多样性。

DOI：
http://dx.10.1371/journal.pbio.1001889
发表时间：
2014
期刊：
PLoS biology
影响因子：
9.8
作者：
Keeling PJ
通讯作者：
Keeling PJ

Ocean acidification with (de)eutrophication will alter future phytoplankton growth and succession.

海洋酸化和富营养化（去）化将改变未来浮游植物的生长和演替。

DOI：
http://dx.10.1098/rspb.2014.2604
发表时间：
2015
期刊：
Proceedings. Biological sciences
影响因子：
0
作者：
Flynn KJ
通讯作者：
Flynn KJ

Reduced H+ channel activity disrupts pH homeostasis and calcification in coccolithophores at low ocean pH.

H 通道活性降低会破坏低海洋 pH 值下颗石藻的 pH 稳态和钙化。

DOI：
http://dx.10.1073/pnas.2118009119
发表时间：
2022
期刊：
Proceedings of the National Academy of Sciences of the United States of America
影响因子：
11.1
作者：
Kottmeier DM
通讯作者：
Kottmeier DM