What factors control coccolithophore growth rates?

球石生物体是一组独特的微小海洋藻类，它们产生小规模的CaCO3(球藻)，形成细胞周围的外壳(球藻)。球石在海洋碳循环中发挥着重要作用，因为它们将二氧化碳转化为有机物(通过光合作用)和碳酸钙(通过钙化)，而球石是将二氧化碳作为碳酸钙(方解石)从表层转移到深海的有效媒介。球石也比有机物重，会增加下沉物质的重量，因此它们也会到达深海。虽然球石生物有丰富的化石记录，但它们面临着黯淡和不确定的未来--大气中二氧化碳的增加将导致海洋酸化和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源(阳光)和养分(氮、磷)的可获得性。然而，目前还不完全了解海洋化学或光和营养物质的可获得性如何影响今天海洋中的球藻生物体的生长，在这一差距得到解决之前，很难充分认识或预测球藻生物体可能如何应对气候变化。由于方解石和有机质都包含在球石细胞内，在检查球石细胞生长时，两者都需要考虑：了解球石细胞如何平衡细胞水平和这两种材料的生产速率，是了解它们在海洋碳循环中的生长和作用的关键。该项目的目的是通过研究海洋中的天然球虫群落和实验室中生长的单个物种来解决这些不足。为了检查方解石和有机物的细胞水平、光合作用和钙化作用以及生长速度，有必要仔细观察球囊、球囊和内部有机细胞的结构。将海洋球藻群落的知识与实验室中在更受控制的条件下生长的球藻群落的知识结合起来，将形成对球石菌群生长的基本原理的概述。该项目的最终目标将是利用这一概览来生成一个数学模型，该模型描述与球虫球体/细胞结构以及光和营养的可获得性有关的球虫体的生长。这样的模型就可以用来解决全球问题，如球虫生态、它们在海洋碳循环中的作用以及它们在不断变化的气候中的未来。

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.