Collaborative Research: The Paradox of Salt Marshes as a Source of Alkalinity and Low pH, High Carbon Dioxide Water to the Ocean: A First In-depth Study of A Diminishing Source

沼泽等植被繁茂的沿海系统的碳排放量在生物圈中名列前茅。解决沼泽产生的碳并评估其对沿海碳循环的影响，对于确定海洋酸化和富营养化等全球变化的长期影响至关重要。在这个项目中，研究人员将使用新的方法来改进对盐沼碳排放的评估。总体目标是了解沿海湿地在改变沿海海洋的碳酸盐化学、碱度和碳收支方面的作用，以及它们缓冲人类活动驱动的化学变化(如海洋酸化)的能力。该项目将包括对本科生、研究生和博士后研究人员的培训，并将为来自当地美洲原住民部落的学生提供教育机会。潮水与潮间带盐沼交换后，含有较高的总碱度(TA)、较高的二氧化碳含量，但pH较低。这些高生产力、植被繁茂的湿地被认为同时向海洋输出碱度和溶解的无机碳(DIC)。这造成了一个明显的悖论，即盐沼既是海洋的酸化来源，也是海洋的碱化来源。有限的研究表明，沼泽DIC和碱度出口通量可能是区域和全球碳收支中的重要参与者，但目前的估计仍然太不确定，不能得出结论。不幸的是，由于海平面上升、土地开发、富营养化和其他人为压力，潮汐沼泽生态系统在最近几年急剧减少，并可能进一步减少。为了评估这一未来变化的潜在影响，必须了解其当前状况，并准确评估其对碳循环其他部分的意义。同样，对沼泽通过潮汐交换输出的DIC和碱度的不同来源知之甚少，尽管已经指出了好氧和各种厌氧呼吸过程。在这项研究中，研究人员将利用新的方法进行深入研究，通过潮汐交换极大地提高潮间带盐沼的出口通量，从几分钟到一年的尺度，表征和评估沼泽输出的TA的组成(碳酸盐和非碳酸盐碱度)，DOC池在改变碳酸盐化学和输出通量中的作用和意义，确定潮水中DIC的来源，并调查沼泽输出TA和DIC如何影响碳酸盐化学和沿海水域的碳碱平衡。

Carbon production in vegetated coastal systems such as marshes is among the highest in the biosphere. Resolving carbon production from marshes and assessing their impacts on coastal carbon cycling are critical to determining the long-term impacts of global change such as ocean acidification and eutrophication. In this project, researchers will use new methods to improve the assessment of carbon production from salt marshes. The overarching goals are to understand the role of coastal wetlands in altering carbonate chemistry, alkalinity, and carbon budgets of the coastal ocean, as well as their capacity to buffer against anthropogenically driven chemical changes, such as ocean acidification. This project will involve training for undergraduate, graduate, and postdoctoral researchers, and will provide educational opportunities for students from a local Native American tribe. Tidal water, after exchange with intertidal salt marshes, contains higher total alkalinity (TA), higher carbon dioxide, but lower pH. These highly productive, vegetated wetlands are deemed to export both alkalinity and dissolved inorganic carbon (DIC) to the ocean. This creates an apppartent paradox in that salt marshes are both an acidifying and alkalizing source to the ocean. Limited studies suggest that marsh DIC and alkalinity export fluxes may be a significant player in regional and global carbon budgets, but the current estimates are still far too uncertain to be conclusive. Unfortunately, tidal marsh ecosystems have dramatically diminished in the recent past, and are likely to diminish further due to sea level rise, land development, eutrophication, and other anthropogenic pressures. To assess the potential impacts of this future change, it is imperative to understand its current status and accurately evaluate its significatce to other parts of the carbon cycle. Similarly, little is know about the distinct sources of DIC and alkalinity being exported from marshes via tidal exchange, although aerobic and various anaerobic respiration processes have been indicated. In this study, researchers will undertake an in-depth study using new methods to vastly improve export fluxes from intertidal salt marshes through tidal exchange over minutes to annual scales, characterize and evaluate the compostiion (carbonate versus non-carbonate alkalinity) of marsh exported TA, the role and significance of the DOC pool in altering carbonate chemistry and export fluxes, identify sources of DIC being exported in tidal water, and investigate how marsh export of TA and DIC impacts carbonate chemistry and the carbon and alkalinity budgets in coastal waters.