PARTIcle Transformation and Respiration Influence on ocean Carbon Storage

海洋中的碳含量是大气中的50倍。生物过程有助于在与气候相关的时间尺度（数百至数千年）内将碳储存在海洋中。海洋浮游植物（漂浮的微型植物）利用阳光和海洋上层的二氧化碳形成富含碳的身体。当浮游植物死亡时，它们可能会聚集在一起并沉入海洋内部，或者它们可能会被浮游动物（微小动物）吃掉，这些浮游动物会产生能够迅速下沉的粪便颗粒。一旦这些有机碳在水中更深处，细菌可能会殖民这些颗粒并将其分解，或者它们可能会被以它们为食的浮游动物分解。这些过程都是为了减少到达深海的有机碳的数量，但是它越深，它与大气接触的时间就越长。这种“生物碳泵”有助于调节我们的气候，如果没有海洋中的生物，大气中的二氧化碳水平可能会比现在高出近一倍。地球系统模型对生物碳泵的描述各不相同，但都相当简单，因为缺乏对颗粒形成和呼吸功能的理解。为政府间气候变化专门委员会报告提供资料的一套模型没有就未来气候情景下海洋碳储存变化的幅度或方向达成一致。这意味着我们对未来海洋碳储存预测的信心很低，这进一步受到模型和观测之间日益增长的差异的阻碍。在这个项目中，我们将研究有多少碳在从上层海洋过境期间被呼吸，以及以何种方式被呼吸。我们将测量颗粒破碎和聚集，微生物呼吸，浮游动物垂直迁移和呼吸的重要过程。我们将使用过程巡航和自主水下航行器来实现这一目标。我们试图回答这样一个问题：有机物质是如何通过中层生物相互作用转化和呼吸的，这如何随深度，位置和季节而变化，以及海洋碳储存的后果是什么？最终目标是产生新的详细了解的重要过程，影响的速率和深度的内部呼吸，我们将扩大规模，以提供全球解决的信息，需要开发下一代的地球化学模型。

The ocean holds fifty times as much carbon as is in the atmosphere. Biological processes contribute to storing carbon in the ocean on climate-relevant timescales (hundreds to thousands of years). Marine phytoplankton (drifting microscopic plants) use sunlight and carbon dioxide in the upper ocean to form their bodies which are rich in carbon. When phytoplankton die they might clump together and sink into the ocean interior, or they could be eaten by zooplankton (tiny animals) which produce fecal pellets that can sink rapidly. Once this organic carbon is deeper in the water, bacteria might colonise the particles and break them down, or they could be broken apart by zooplankton feeding on them. These processes all act to reduce the amount of organic carbon reaching the deep ocean, however the deeper it goes the longer it will remain out of contact with the atmosphere. This "biological carbon pump" helps to regulate our climate, and without biology in the ocean it has been shown that atmospheric carbon dioxide levels could be nearly double what they are today.Earth system models have differing, but all fairly simple, representations of the biological carbon pump due to a lack of understanding of how the processes contributing to particle formation and respiration function. The suite of models that contribute to the Intergovernmental Panel on Climate Change reports do not agree on the magnitude or direction of change for ocean carbon storage under future climate scenarios. This means we have low confidence for our future projections of ocean carbon storage, which is further impeded by a growing discrepancy between models and observations. In this project we will examine how much carbon has been respired during the transit from the upper ocean, and in what ways. We will measure the important processes of particle fragmentation and aggregation, microbial respiration, and zooplankton vertical migration and respiration. We will do this using a process cruise and autonomous underwater vehicles. We seek to answer the question: How is organic matter transformed and respired by biotic interactions in the mesopelagic, how does that vary with depth, location and season, and what are the consequences for ocean carbon storage? The ultimate goal is to generate new detailed understanding of important processes that influence the rate and depth of interior respiration which we will scale up to provide the globally-resolved information needed to develop the next generation of biogeochemical models.