What factors control coccolithophore growth rates?

颗石藻是一组独特的微小海洋藻类，产生小规模的CaCO 3（颗石），形成细胞周围的外壳（颗石球）。颗石藻在海洋碳循环中起着重要作用，因为它们将CO2转化为有机物质（通过光合作用）和CaCO 3（通过钙化），而颗石藻是将CO2以CaCO 3（方解石）形式从表面转移到深海的有效媒介。颗石也比有机物质重，并增加下沉物质的重量，使其也到达深海。虽然颗石藻有着丰富的化石记录，但它们面临着暗淡和不确定的未来-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量（阳光）和营养物质（氮，磷）的可用性。然而，海洋化学或光和营养物质的可用性如何影响颗石藻在当今海洋中的生长尚未完全了解，在解决这一差距之前，很难充分了解或预测颗石藻如何对气候变化作出反应。由于包含方解石和有机物质的coccolithophore细胞内，都需要考虑当检查coccolithophore生长：了解coccolithophore如何平衡细胞水平和生产率的这两种材料是关键，了解他们的增长和海洋碳循环中的作用。该项目的目的是通过研究海洋中的天然颗石藻群落和实验室中生长的单个物种来解决这些缺陷。为了研究方解石和有机物的细胞水平，光合作用和钙化，以及生长速率，有必要仔细观察球球体，颗石和内部有机细胞的结构。结合海洋颗石群落的知识和在实验室中更受控的条件下生长的知识，将创建一个管理颗石生长的原理的概述。该项目的最终目标是利用这一概述生成一个数学模型，描述颗石藻生长与颗石球/细胞结构以及光和营养物质的可用性的关系。这样一个模型可以用来解决全球性的问题，如颗石藻生态学、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.