Will Ocean Acidification Diminish Particle Aggregation and Mineral Scavenging, Thus Weakening the Biological Pump?

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。由于大气中二氧化碳的增加，预计未来50到100年内，海洋的PH值将下降0.2-0.5pH单位。到目前为止，几乎所有关于即将到来的海洋酸化的研究都集中在对钙化生物和碳酸盐系统的影响上。然而，海洋酸化也将影响其他与pH有关的重大海洋过程。在这个项目中，加州大学圣巴巴拉分校的研究人员将调查海洋酸化对有机碳或软组织生物泵的影响。他们预测，海洋pH值的下降将导致负电荷物质质子化的增加，特别是透明胞外聚合物颗粒(TEP)的质子化，TEP是一种凝胶状颗粒，提供聚集体的基质并将颗粒结合在一起。这些高表面活性颗粒的极性降低可能会降低它们的“粘性”，导致富含有机物质的颗粒聚集减少，聚集体清除和保留重压载矿物的能力降低。团聚体的减少将降低包含在快速下沉的团聚体中的POC的比例。集合体对矿物的清除减少将导致下沉速度降低，从而导致物质在水柱中逃逸降解的比例下降。这两个过程最终都会将碳通量减少到深度。由此导致的生物泵的削弱将改变远洋生态，并可能产生一个正反馈途径，进一步增加大气中的二氧化碳浓度。研究小组将通过实验研究TEP的产生量、聚集率和聚集体特征、矿物清除和下沉速度作为海洋酸化的函数，因为这些参数对pH敏感，并且在决定有机碳的沉积速率时起中心作用。他们将确定TEP的非生物形成或TEP或TEP前体的释放速率的潜在变化，这些浮游植物已经适应了多代二氧化碳增加的制度，最多增加了1000倍。此外，他们将在实验中测试适应的浮游植物和自然颗粒聚集率的潜在变化，并测量聚集体对压载矿物清扫率的影响。还将确定各种酸化程度对集料特性的影响，包括集料的大小、组成、密度和下沉速度。这些结果有望为预测模型提供参数，该模型将用于研究改变压载或聚集对碳通量的影响。更广泛的影响：气候和环境变化是对社会的全球性挑战。我们需要知道，生物泵的正反馈机制是否会进一步增加大气中的二氧化碳，以便为未来的气候变化做准备，并有望对其进行管理。该项目还将促进美国和欧洲科学家之间的国际合作，并对(女性)学生的培训做出显著贡献。结果将提供给当地的K-12教室和公众，以提高公众对海洋酸化对海洋生态系统的潜在影响的认识。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The pH of the ocean is predicted to decrease by 0.2-0.5 pH units in the next 50 to100 years as a result of increasing atmospheric CO2. To date almost all the research on impending ocean acidification has focused on the impacts to calcifying organisms and the carbonate system. However, ocean acidification will also affect other significant marine processes that are pH dependent. In this project, researchers at the University of California at Santa Barbara will investigate the impact of ocean acidification on the organic carbon or 'soft tissue' biological pump. They predict that a decline in oceanic pH will result in an increase in the protonation of negatively charged substances, especially of Transparent Exopolymer Particles (TEP), the gel-like particles that provide the matrix of aggregates and bind particles together. A decreased polarity of these highly surface-active particles may reduce their "stickiness" resulting in decreased aggregation of organic-rich particles and a decreased ability of aggregates to scavenge and retain heavy ballast minerals. A reduction in aggregation will lower the fraction of POC enclosed in fast-sinking aggregates. Decreased scavenging of minerals by aggregates will result in reduced sinking velocities and consequently a decline in the fraction of material escaping degradation in the water column. Both processes ultimately reduce carbon flux to depth. The resulting weakening of the biological pump will alter pelagic ecology and potentially produce a positive feed-back pathway that further increases atmospheric CO2 concentrations. The research team will experimentally investigate TEP-production, aggregation rates and aggregate characteristics, mineral scavenging and sinking velocity as a function of ocean acidification, because these parameters are susceptible to pH and central in determining sedimentation rate of organic carbon. They will determine potential changes in the abiotic formation of TEP or in the release rate of TEP or TEP-precursors by phytoplankton that have been adapted to increased CO2 regimes for multiple generations, up to 1000 doublings. Additionally, they will experimentally test potential changes in the aggregation rate of adapted phytoplankton and natural particles, and measure impacts on scavenging rates of ballast minerals by aggregates. Effects of various acidification levels on aggregate characteristics, including size, composition, density, and sinking velocity will also be determined. These results are expected to provide parameterization for a predictive model that will be used to investigate the impact of changing ballasting or aggregation on carbon flux. Broader impact: Climate and environmental change are a global challenge to society. We need to know if possible positive feed back mechanisms to the biological pump will further increase atmospheric CO2 in order to prepare for and hopefully manage future climate changes. This project will also foster international collaboration between scientists in the US and Europe and contribute appreciably to the training of (female) students. Results will be made available to local K-12 classrooms and to the general public to increase public awareness of the potential impacts of ocean acidification on marine ecosystems.