Inductively coupled plasma - optical emission spectrometry of pond sediments, Copper River Delta, AK: collected in 2017, measured in 2022

High-latitude, coastal wetland biogeochemistry is dynamic in response to climate change, and yet we do not understand, and thus cannot fully predict, how crucial aspects of these systems will change in the future. Temperatures in the Northern Hemisphere have disproportionately increased 4° Celsius (C) in 30 years causing the rate of deglaciation to increase significantly in global high-latitude river deltas. This will have a prolonged effect on local microbiome metabolism and biodiversity of the subsurface, influencing solid, liquid, and gaseous compounds in the system. Using sediment geochemical analyses, autonomous sampling techniques, and 16S rRNA (Ribosomal ribonucleic acid) gene sequencing, we have identified key processes that occur in the Copper River Delta, AK (Alaska), a model system to study high-latitude watersheds during rapid climate change. We calculated carbon accumulation rates upwards of 520 ± 60 grams (g) C per meter squared per year (m-2 yr-1) in outwash pond sediments nearest to the glaciers, which co-occurred with pronounced suboxic peaks in Iron (Fe) (III) and Manganese (Mn) (II). Sediment microbial communities across the outwash ponds are structured on the basis of total iron and manganese concentrations, proximity to glaciers, and organic matter content. Additionally, we revealed no methane accumulation in the ponds during ice-cover, despite high organic matter content. High-latitude wetland ecosystems are not only influenced by the changing climate, but also have the potential to impact carbon cycling considering high carbon burial rates. These findings show the importance of understanding changing biogeochemical processes in high-latitude wetlands, as they have the potential to influence carbon cycling.

高纬度滨海湿地生物地球化学过程随气候变化呈现动态特征，但目前我们尚未明确其核心调控机制，因此无法全面预测该类生态系统未来的关键演变趋势。近30年来，北半球气温异常升高4摄氏度，致使全球高纬度河口三角洲的冰川消退速率显著加快。这一变化将对当地地下微生物组代谢与生物多样性产生长期影响，进而改变系统内固态、液态与气态化合物的循环过程。本研究依托沉积物地球化学分析、自主采样技术以及16S核糖体核糖核酸（16S rRNA, Ribosomal ribonucleic acid）基因测序技术，在阿拉斯加州（Alaska, AK）铜河三角洲这一快速气候变化背景下高纬度流域研究的典型模式系统中，明确了其内部发生的关键生物地球化学过程。针对紧邻冰川的冰碛池塘沉积物，我们测得其碳累积速率可达520±60克碳·平方米⁻¹·年⁻¹，同时检测到显著的三价铁（Fe³+）与二价锰（Mn²+）亚氧峰值。各冰碛池塘的沉积物微生物群落结构，主要受总铁、总锰浓度、与冰川的空间距离以及有机质含量的调控。此外，尽管池塘内有机质含量较高，但我们发现冰封期的池塘并未出现甲烷累积现象。高纬度湿地生态系统不仅受气候变化的直接影响，同时因其较高的碳埋藏速率，具备调控全球碳循环的潜力。本研究结果凸显了明晰高纬度湿地生物地球化学过程演变的重要性——这类生态系统的变化或将对全球碳循环产生显著影响。