Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin
Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin
复制标题
DOI：
10.1002/2017gb005699
复制
发表时间：
2017-08
影响因子：
5.2
通讯作者：
B. Voss;K. Wickland;G. Aiken;R. Striegl
中科院分区：
文献类型：
--
作者：
B. Voss;K. Wickland;G. Aiken;R. Striegl
河流生态系统从陆地吸收有机质，在内部产生新的有机质，并进行生物地球化学循环，修饰有机碳和无机碳。对河流系统中碳源与处理之间关系的理解仍然存在重大差距。本文综合了明尼苏达州瓦巴沙上游密西西比河（UMR）系统中溶解有机碳（DOC）、颗粒有机碳（POC）和溶解无机碳（DIC）的同位素、元素和分子性质，包括密西西比河干流及其四条主要支流（明尼苏达州、密西西比河上游、圣克罗伊河和奇佩瓦河）。我们的目标是阐明生物过程如何改变水生碳库的化学和同位素组成，在具有自然和人工蓄水的大型河流系统中向下游运输。土地覆盖与DOC碳同位素组成、吸光度和疏水酸含量的关系表明，DOC保留了陆地碳源信息，而陆地POC信号在很大程度上被原生有机质所取代，DIC整合了水体中有机质光合作用和呼吸作用的影响。UMR全年略有异养，但由低水头通航大坝和天然蓄水池形成的水池促进了向自养条件的转变，改变了水生生态系统动力学和POC和DIC组成。这种变化可能发生在所有受低水头水坝影响的主要河流系统中，并且需要纳入我们对内陆水碳动态和控制河流二氧化碳排放过程的理解，因为未来河流和水资源管理计划了新的导航和防洪系统。
Riverine ecosystems receive organic matter (OM) from terrestrial sources, internally produce new OM, and biogeochemically cycle and modify organic and inorganic carbon. Major gaps remain in the understanding of the relationships between carbon sources and processing in river systems. Here we synthesize isotopic, elemental, and molecular properties of dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in the Upper Mississippi River (UMR) system above Wabasha, MN, including the main stem Mississippi River and its four major tributaries (Minnesota, upper Mississippi, St. Croix, and Chippewa Rivers). Our goal was to elucidate how biological processing modifies the chemical and isotopic composition of aquatic carbon pools during transport downstream in a large river system with natural and man‐made impoundments. Relationships between land cover and DOC carbon‐isotope composition, absorbance, and hydrophobic acid content indicate that DOC retains terrestrial carbon source information, while the terrestrial POC signal is largely replaced by autochthonous organic matter, and DIC integrates the influence of in‐stream photosynthesis and respiration of organic matter. The UMR is slightly heterotrophic throughout the year, but pools formed by low‐head navigation dams and natural impoundments promote a shift toward autotrophic conditions, altering aquatic ecosystem dynamics and POC and DIC compositions. Such changes likely occur in all major river systems affected by low‐head dams and need to be incorporated into our understanding of inland water carbon dynamics and processes controlling CO2 emissions from rivers, as new navigation and flood control systems are planned for future river and water resources management.