What factors control coccolithophore growth rates?

球石藻是一种独特的微型海洋藻类，它们产生小尺度的CaCO3（球石），在细胞周围形成一个外壳（球球）。球石藻在海洋碳循环中具有重要作用，它们将CO2转化为有机物（通过光合作用）和CaCO3（通过钙化），并且球石藻是将CO2作为CaCO3（方解石）从海洋表面转移到深海的有效媒介。球粒岩也比有机物重，增加了下沉物质的重量，使其也能到达深海。尽管颗石藻有丰富的化石记录，但它们面临着一个黯淡而不确定的未来——大气中二氧化碳的增加将导致海洋酸化和一个不利于钙化生物的化学环境，而全球变暖将改变海洋的混合方式以及生长所需的能量（阳光）和营养物质（氮、磷）的可用性。然而，目前尚不完全了解海洋化学或光和营养物质的可用性如何影响当今海洋中的球石藻生长，并且在解决这一空白之前，很难充分了解或预测球石藻如何对气候变化作出反应。由于球粒石细胞中包含方解石和有机物，因此在检查球粒石生长时需要考虑这两种物质：了解球粒石如何平衡这两种物质的细胞水平和生产速率是了解其生长及其在海洋碳循环中的作用的关键。该项目的目的是通过研究海洋中的天然球石藻群落和实验室中生长的单个物种来解决这些缺陷。为了检查方解石和有机物的细胞水平、光合作用和钙化以及生长速度，有必要仔细观察球球、球石和内部有机细胞的结构。将海洋颗石藻群落的知识与实验室中更受控制的条件下生长的知识相结合，将对控制颗石藻生长的主要因素进行概述。该项目的最终目标是利用这一概述来生成一个数学模型，该模型描述了球球团/细胞结构以及光和营养的可用性与球球团生长的关系。这样的模型可以用来解决关于颗石藻生态学的全球性问题，它们在海洋碳循环中的作用以及它们在气候变化中的未来。

Coccolithophores are a unique group of microscopic marine algae that produce small scales of CaCO3 (coccoliths), which form an outer shell (coccosphere) around the cell. Coccolithophores have important roles in the marine carbon cycle as they convert CO2 into both organic matter (via photosynthesis) and CaCO3 (via calcification), and coccoliths are effective agents at transferring CO2 as CaCO3 (calcite) from the surface to deep ocean. Coccoliths are also heavier than organic matter and add weight to sinking material so that it also reaches the deep sea. Although coccolithophores have a rich fossil record they face a bleak and uncertain future - increased atmospheric CO2 will cause ocean acidification and a chemical environment unfavourable to calcifying organisms, while global warming will change how the oceans are mixed and the availability of energy (sunlight) and nutrients (nitrogen, phosphorus) needed for growth. However, it is not fully understood how ocean chemistry or the availability of light and nutrients effects coccolithophore growth in the present-day ocean, and until this gap is addressed it is difficult to fully appreciate or predict how coccolithophores may react to climate change. Due to the inclusion of both calcite and organic matter within coccolithophore cells, both need to be considered when examining coccolithophore growth: understanding how coccolithophores balance cellular levels and rates of production of these two materials is key to understanding their growth and role in the marine carbon cycle. The aim of this project is to address these deficiencies by studying both natural coccolithophore communities in the ocean and individual species grown in the laboratory. In order to examine cellular levels of calcite and organic matter, photosynthesis and calcification, and growth rates it will be necessary to look closely at the structure of the coccosphere, coccolith and inner organic cell. The combination of knowledge from oceanic coccolithophore communities and those grown under more controlled conditions in the laboratory will create an overview of the principals governing coccolithophore growth. The end goal of this project will be to use this overview to generate a mathematical model that describes coccolithophore growth in relation to the coccosphere/cell structure and the availability of light and nutrients. Such a model can then be used to address global questions about coccolithophore ecology, their role in the marine carbon cycle and their future in a changing climate.