The Biological Carbon Pump in the Anthropocene

我的DG提案的三个主要目标是我了解生物碳泵（BCP）这一更大目标的核心组成部分，这样我们就可以(a)评估它在污染物分布中的作用，(b)确定海洋固碳能力可能会如何变化。自工业革命以来，海洋已经吸收了25-30%的人为碳，但目前尚不清楚随着大气二氧化碳分压的增加，海洋是否会继续吸收碳。目标1：确定西北大西洋BCP重力沉降粒子通量路径的强度：尽管拉布拉多海在全球碳循环以及表层和深海之间的氧气和二氧化碳交换中发挥着核心作用，但我们对该区域重力粒子沉降的作用和变异性以及该通量随深度的损失率的了解极为有限。对系泊时间序列沉积物捕集器样本的仔细分析将提供关于通量类型和强度以及通量衰减的季节性变化的信息。为深海生物提供食物来源的沉物的营养价值将被研究。营养价值的严重变化将影响食物网，包括具有商业价值的鱼类。目的2：确定浮游植物对多种应激源的反应模式，例如温度、光和碳酸盐化学的变化。近年来的研究表明，浮游植物对几种同时发生的应激源的反应不是相加的，而是复杂的，需要有针对性的实验来研究影响生长、聚集和沉积的相互作用反应。通常只研究单一的胁迫源和浮游植物的生长阶段。由于浮游植物初级生产提供了最大的理论通量潜力，生产力、聚集和沉积的变化将推动BCP功能的变化，以及海洋吸收二氧化碳的潜力。冰的流失有可能改变沉积模式，因为冰藻及其渗出物会导致冰缘下沉。这些机制将进行实验研究。目的3：表征聚集体对微塑料的运输和命运的作用。最初的实验表明，小的塑料颗粒可能与快速下沉的聚集体结合在一起，将它们运送到海底，在那里底栖生物和以它们为食的生物暴露在外。由于塑料的密度比海水小，这条道路是出乎意料的，而且在很大程度上没有被探索过。详细的聚集实验和对沉积物捕集器中收集的下沉物质的分析相结合，将得出塑料的沉积模式，并深入了解驱动其通量的机制。了解这些分布途径是减轻和清理海洋塑料污染的先决条件，这是加拿大在“零塑料废物战略”中承诺的。

The three main objectives of my DG proposal are central components to my larger goal to understand the Biological Carbon Pump (BCP), so that we may (a) evaluate its role in the distribution of pollutants and (b) determine how the ability of the ocean to sequester carbon may change. Since the industrial revolution the ocean has taken up 25-30% of anthropogenic carbon, yet it is unclear whether the ocean will continue to take up carbon as atmospheric pCO2 is increasing. Objective 1: Determine the strength of the gravitational settling particle flux pathway of the BCP in the North-West Atlantic: Although the Labrador Sea plays a central role in the global carbon cycle, as well as in the exchange of oxygen and CO2 between the surface and deep ocean, our knowledge of the role and variability of gravitational particle sinking and the loss rate of this flux with depths, is extremely limited for this region. Careful analysis of samples from moored, time-series sediment traps will provide information on seasonal variability of flux type and strength and of flux attenuation. Nutritional value of sinking matter, which provides the food source for organisms at depths will be investigated. Severe changes in nutritional value would impact food webs, including commercially valuable fish. Objective 2: Identify response patterns of phytoplankton to multiple stressors, e.g. shifts in temperature, light and carbonate chemistry. Recent research efforts have revealed that the response of phytoplankton to several simultaneous stressors is not additive, but complex, requiring targeted experiments to investigate interactive responses affecting growth, aggregation and sedimentation. Commonly only a single stressor and only the growth phase of phytoplankton are investigated. As phytoplankton primary production provides the maximum theoretical flux potential, changes in productivity, aggregation and sedimentation will drive shifts in the functioning of the BCP, and the potential for the ocean to sequester CO2. Loss of ice has the potential to alter sedimentation patterns, as ice algae and their exudates cause sinking ice edge blooms. These mechanisms will be investigated experimentally. Objective 3: Characterize the role of aggregation for the transport and fate of micro-plastics. Initial experiments show that small plastic particles may be incorporated into rapidly sinking aggregates, transporting them to the seafloor where benthic organisms and those feeding on them are exposed. As plastics are less dense than seawater, this pathway is unexpected and largely unexplored. A combination of detailed aggregation experiments and analysis of sinking material collected in sediment traps, will yield sedimentation patterns of plastic, and give insights to mechanisms driving their flux. Understanding these distribution pathways is a prerequisite for the mitigation and clean up of plastic pollution in the ocean, which Canada has pledged to in the "strategy on zero plastic waste".