Role of phytoplankton community structure in determining the efficiency of the ocean's biological carbon pump

由于人类活动，越来越多的二氧化碳正在进入大气层。浮游植物是生活在海洋中的微小植物，它消耗二氧化碳，将其从空气中吸收到海洋中。但要想让二氧化碳的减少对大气水平产生长期影响，碳必须被锁在海洋的深水中，远离空气。碳转移到深水的一种方式是通过死亡浮游生物下沉的身体。海洋学家用固定在海底的沉淀物捕集器测量颗粒的流量。但并不是浮游生物在表面产生的所有碳都到达了陷阱。这样做的百分比被称为转移效率。这已被发现随着时间的推移而变化，即在不同的季节和年份，以及在不同的地点。一个可能的原因是从表面下沉的浮游生物类型不同。有两种类型的浮游生物被认为在改变转移效率方面起着关键作用：硅藻和球藻。硅藻是由硅石组成的大型浮游生物，而球石生物体主要是方解石。硅藻被认为比球藻下沉得更快，但由于它们的化学组成不同，在海水中也可能溶解得更快。研究这一过程的困难在于，需要在大范围和长时间段内测量浮游生物的碳产量和物种。要研究这一问题，需要结合使用船只、绕地卫星和海洋模型进行测量。船只能够对海洋进行测量，这是我们用其他任何方法都无法获得的，但无法在大片区域或多年内进行采样。一种名为海洋颜色的卫星数据测量了生活在海面附近的浮游生物的数量。由于卫星每天拍摄一次周围大片海洋的快照，我们可以调查浮游生物分布的空间模式，以及它们在几个月和几年中的变化。但卫星只能看到表面的海洋，所以要了解海底正在发生的事情，还需要一个海洋模型。然后我们就可以研究浮游生物种类的变化对到达深水的物质的影响。将所有这些不同方法的数据结合在一起，将为几年来转移效率的变化以及浮游生物物种的变化可能产生的影响提供新的见解。随着全球气候变化，世界海洋的不同部分预计将以不同的方式做出反应，因此将研究北大西洋四个不同的地点，以了解过去表面条件的变化如何影响转移效率。这将有助于我们预测未来气候变化可能如何影响二氧化碳从大气转移到北大西洋深海的速度。

Increasing amounts of CO2 are entering the atmosphere because of human activity. Phytoplankton, tiny plants that live in the ocean, consume CO2, drawing it down from the air into the sea. But for this CO2 drawdown to have a long-term impact on atmospheric levels, the carbon has to be locked away, out of contact with the air, in the deep waters of the ocean. One way carbon is transferred to deep waters is via the sinking bodies of dead plankton. Oceanographers measure this flux of particles with sediment traps moored to the ocean floor. But not all of the carbon produced by plankton at the surface reaches the traps. The percentage that does is referred to as the transfer efficiency. This has been found to vary over time, i.e. in different seasons and years, and at different locations. One possible reason is that the types of plankton sinking from the surface are different. Two types of plankton are thought to play critical roles in altering the transfer efficiency: diatoms and coccolithophores. Diatoms are large plankton made of silica, whilst coccolithophores are mostly calcite. Diatoms are thought to sink more quickly than coccolithophores, but may also dissolve more quickly in seawater, due to the differences in their chemical make-up. The difficulty in studying this process is that measurements of plankton carbon production and species are needed over large areas and long time periods. A combination of measurements using ships, satellites orbiting the Earth and models of the ocean are needed to study this problem. Ships are able to make measurements of the ocean that we cannot get any other way, but cannot sample over large areas or for multiple years. One type of satellite data, ocean colour, measures the amount of plankton living near the sea surface. Because satellites take a snapshot of a large area of ocean around once a day, we can investigate the spatial patterns of plankton distribution, and how they change over months and years. But satellites only see the surface ocean, so to understand what is happening at the sea floor an ocean model is also needed. We can then study the effect that changes in plankton species have on the material reaching deep waters. Combining data from all these different methods will give new insight into how the transfer efficiency has varied over several years, and what impact changing plankton species may have had. As global climate changes, different parts of the world's oceans are expected to respond in different ways, so four contrasting sites in the North Atlantic will be studied to understand how past changes in surface conditions affected the transfer efficiency. This will help us to predict how future climate change may impact the rate of CO2 transfer from the atmosphere to the deep ocean in the North Atlantic.