Quantification of sedimentary oxygen and carbon dioxide dynamics in a dry sandy beach affected by macroalgae deposition

沙滩为濒危物种提供栖息地，保护海岸，并因其高社会和经济价值而受到赞赏。它们正面临着不断升级的人为压力，原因是沿海开发、营养物质增加和全球变暖，近年来全球变暖导致海藻大量繁殖，在世界各地的沙滩上沉积了大量藻类。这项计划调查沉积的藻类的去向及其对海滩生物地球化学环境的影响。藻类的腐烂会在海滩上局部耗尽氧气，产生有毒的硫化物和高浓度的氨气，损害海滩生物，污染近岸水域，并阻止游客。该项目的研究量化了控制藻类分解的生物地球化学和运输过程。生成这些数据是开发模型的先决条件，这些模型可以预测大规模大型藻类沉积的影响，从而支持决策和海岸管理。该项目研究与海洋生物地球化学方法的研究生和本科生指导的教育部分紧密相连，以及一个专门的外展计划，向公众介绍海藻问题和减少这一问题的途径。该项目产生关于沙质海滩干燥的顶端地带(涨潮线和沙丘之间)氧气和二氧化碳分布的动态以及界面气体通量的数据，并确定大型藻类的退化如何影响分布和通量。有机碳和有机氮剖面是碳酸盐和硅酸盐海滩这两个研究地点的生物地球化学沉积环境的特征。一系列实验室实验将气体通量与埋藏的大型藻层的降解率以及气体交换、温度和湿度的影响联系起来。这些数据将使人们能够估计藻类分解过程的时间框架，并提供关于沙滩退化能力的信息。由于海滩沉积O2和CO2的动态和通量在很大程度上没有描述，项目数据有助于从机理和定量上了解沙滩上的碳和养分循环。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Sandy beaches provide habitat for endangered species, protect the coast, and are appreciated for their high social and economic values. They are facing escalating anthropogenic pressures through coastal development, nutrient increases and global warming, which in recent years led to the development of extensive seaweed blooms that deposit massive amounts of algae on sandy beaches worldwide. This project investigates the fate of the deposited algae and their influence on the biogeochemical environment of the beach.The decay of the algae locally depletes oxygen in the beach and produces toxic sulfides and high concentrations of ammonia that harm beach organisms, pollute nearshore waters and deter tourists. Research in this project quantifies biogeochemical and transport processes that control the algal decomposition. Generating these data is prerequisite for developing models that can predict the impact of the massive macroalgal deposition and thereby support decision making and coastal management. The project research is tightly linked to an educational component with instruction of graduate and undergraduate students in marine biogeochemical methods, and a dedicated outreach program informing the public about the seaweed issue and pathways to reduce this problem.The project produces data on the dynamics of oxygen and carbon dioxide distribution and interfacial gas flux in the dry, supralittoral zone (between high tide line and dunes) of sandy beaches and determines how distributions and fluxes are influenced by the degradation of the macroalgae. Organic carbon and nitrogen profiling characterizes the biogeochemical sedimentary environment at the two study sites, a carbonate and a silicate beach. A set of laboratory experiments relates gas fluxes to the degradation rate of buried macroalgal layers and the effects of gas exchange, temperature and moisture. The data will allow estimates of the time frame of the algal decomposition process and provide information on the degradation capacity of sandy beaches. Since beach sedimentary O2 and CO2 dynamics and fluxes are largely undescribed, the project data contribute to the mechanistic and quantitative understanding of carbon and nutrient cycling in sandy beaches.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.