Connecting Hydrology, Biology, and Geochemistry in a Coastal Wetland: Feedbacks between Ecosystem Processes toward Predictive Understanding

沿海沼泽在碳循环中起着至关重要的作用，因为它们储存了大量的碳，并调节了碳在陆地、海洋和大气之间的流动。由于地处陆海边缘，潮汐沼泽受到海平面上升、气候条件变化和人类压力的威胁，这可能会释放出以前储存的碳，并降低它们未来储存碳的能力。由此产生的对碳循环的影响将取决于沼泽水文变化如何影响碳的运动和化学形式，但这些影响目前尚不清楚。本研究探讨了变化的水文条件对沼泽水化学的影响，并将这些影响与潮汐沼泽和沿海海洋之间碳运动的变化联系起来。这项研究改进了对未来碳预算可能如何变化的预测，并使管理者能够更好地保护这些脆弱的沿海生态系统的碳储存潜力。该项目还增加了本科生和研究生的教育机会，并使圣琼斯国家河口研究保护区的发展成为可能，用于课程教学和公众宣传。河口和沼泽是全球重要的碳库，是陆地和海洋相互作用的关键点，是碳和营养物质循环的地方。尽管它们很重要，但水文对生物地球化学的控制，以及反过来对这些生态系统的碳动态的研究相对不足，限制了预测气候变化和海平面上升反馈的能力，限制了对沼泽生态系统服务的评估，限制了在这些脆弱景观中管理人类活动的能力。本项目结合实地、实验室和建模方法，阐明了沿海沼泽的碳动态是如何通过物理和生物地球化学因素之间的相互作用，受到时空复杂水文的驱动的。本研究(1)基于水文学、地下地球化学和生物活动对沼泽进行圈定；(2)建立生物、地球化学和水文因子变化之间的机制联系；(3)将机制信息与水文模型相结合，深入了解水文变化对氧化还原带和相关碳动态的长时间影响。实地分析是在特拉华州多佛的圣琼斯国家河口研究保护区的大西洋中部潮汐沼泽进行的。这项工作填补了水文对沼泽生物地球化学影响的认识空白，并确定了控制沼泽与沿海海洋之间碳动态和通量的具体因素。这项综合研究促进了新的概念和定量模型的发展，以预测沿海系统中生物地球化学和水文变化之间的反馈。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Coastal marshes play a critical role in the carbon cycle because they store vast amounts of carbon and regulate its movement between land, ocean, and atmosphere. Given their position at the land-sea margin, tidal marshes are threatened by rising seas, changing climatic conditions, and human pressures, which may release previously stored carbon and reduce their ability to store carbon in the future. The resulting impacts on the carbon cycle will depend on how changes in marsh hydrology affect the movement and chemical form of carbon, but these impacts are currently unknown. This study explores the impacts of changing hydrologic conditions on marsh water chemistry and links these to changes in carbon movement between tidal marshes and the coastal ocean. The research improves predictions of how carbon budgets may change in the future and enables managers to better protect the carbon storage potential of these fragile coastal ecosystems. The project also enhances education opportunities for undergraduate and graduate students, and enables the development of the St. Jones National Estuarine Research Reserve for course instruction and public outreach.Estuaries and marshes are globally important reservoirs of carbon and the critical points of interaction between land and oceans where carbon and nutrients are cycled. Despite their importance, the hydrological controls on biogeochemistry and, in turn, carbon dynamics of these ecosystems are relatively understudied, limiting the capacity to predict feedbacks with climate change and sea-level rise, to value marsh ecosystem services, and to manage human activities in these fragile landscapes. This project incorporates field, laboratory, and modeling approaches to elucidate how carbon dynamics in coastal marshes are driven by the spatially and temporally complex hydrology through interactions between physical and biogeochemical factors. This research (1) delineates the marsh based on hydrology, subsurface geochemistry, and biological activity, (2) establishes mechanistic linkages between changes in biological, geochemical, and hydrologic factors, and (3) combines mechanistic information with hydrological modeling to gain insights into longer timescale impacts of hydrologic change on redox zonations and associated carbon dynamics. Field analyses are conducted in a mid-Atlantic tidal marsh at the St. Jones National Estuarine Research Reserve in Dover, Delaware. This work fills gaps in the understanding of the hydrologic impacts on marsh biogeochemistry and identifies specific factors controlling carbon dynamics and fluxes between marshes and the coastal ocean. This integrated study promotes development of new conceptual and quantitative models to predict feedbacks between biogeochemistry and hydrologic change in coastal systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.