Dissolved organic matter variations in coastal plain wetland watersheds: The integrated role of hydrological connectivity, land use, and seasonality
Dissolved organic matter variations in coastal plain wetland watersheds: The integrated role of hydrological connectivity, land use, and seasonality
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DOI：
10.1002/hyp.11519
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发表时间：
2018-05-30
影响因子：
3.2
通讯作者：
Palmer, Margaret A.
中科院分区：
文献类型：
--
作者：
Hosen, Jacob D.;Armstrong, Alec W.;Palmer, Margaret A.
溶解有机质（DOM）是河流生物地球化学功能不可或缺的组成部分，湿地被广泛认为是河流网络中芳香DOM的重要来源。然而，土地利用变化如何改变高地湿地与溪流的生物地球化学连通性仍不清楚。我们研究了美国德尔马瓦半岛上地理上孤立的洼地湿地，这些湿地通过临时通道季节性地与下游多年生水域相连。对4个森林湿地、4个农业湿地和4个恢复湿地的DOM组成和数量进行了评价。在地表连接存在和不存在的时期，还对20条流域含有湿地的多年生河流进行了DOM采样。多年生流域有不同数量的森林湿地（0.4-82%）和农业（1-89%）覆盖。采用紫外可见光谱、荧光光谱、溶解有机碳（DOC）浓度和生物测定法对DOM进行分析。与农业湿地和恢复湿地相比，森林湿地输出的DOM更多，且芳香性更强。后两者的DOM无法区分，表明恢复湿地恢复有限；两者的DOM比森林湿地的DOM更像蛋白质。湿地覆盖面积最大的多年生河流，各季节DOC水平最高；然而，在秋季和冬季，当临时溪流将森林湿地与多年生河道连接时，多年生DOC浓度达到峰值，并且组成与森林湿地有关。夏季临时河道干枯时，多年生DOC浓度最低，蛋白质样DOM含量最高。总体而言，多年生河流中DOC水平与湿地土地覆盖总量有关，但DOM峰值通量的时间由湿地与多年生河流的连通性驱动。生物测定表明，与农业用地相关的蛋白质样DOM相比，与湿地相关的DOM在微生物利用方面的可用性更低。综上所述，这些证据表明地理上孤立的湿地对下游水质和生态系统功能有显著的影响，这些影响是由河流表面临时连接介导的。
Dissolved organic matter (DOM) is integral to fluvial biogeochemical functions, and wetlands are broadly recognized as substantial sources of aromatic DOM to fluvial networks. Yet how land use change alters biogeochemical connectivity of upland wetlands to streams remains unclear. We studied depressional geographically isolated wetlands on the Delmarva Peninsula (USA) that are seasonally connected to downstream perennial waters via temporary channels. Composition and quantity of DOM from 4 forested, 4 agricultural, and 4 restored wetlands were assessed. Twenty perennial streams with watersheds containing wetlands were also sampled for DOM during times when surface connections were present versus absent. Perennial watersheds had varying amounts of forested wetland (0.4-82%) and agricultural (1-89%) cover. DOM was analysed with ultraviolet-visible spectroscopy, fluorescence spectroscopy, dissolved organic carbon (DOC) concentration, and bioassays. Forested wetlands exported more DOM that was more aromatic-rich compared with agricultural and restored wetlands. DOM from the latter two could not be distinguished suggesting limited recovery of restored wetlands; DOM from both was more protein-like than forested wetland DOM. Perennial streams with the highest wetland watershed cover had the highest DOC levels during all seasons; however, in fall and winter when temporary streams connect forested wetlands to perennial channels, perennial DOC concentrations peaked, and composition was linked to forested wetlands. In summer, when temporary stream connections were dry, perennial DOC concentrations were the lowest and protein-like DOM levels the highest. Overall, DOC levels in perennial streams were linked to total wetland land cover, but the timing of peak fluxes of DOM was driven by wetland connectivity to perennial streams. Bioassays showed that DOM linked to wetlands was less available for microbial use than protein-like DOM linked to agricultural land use. Together, this evidence indicates that geographically isolated wetlands have a significant impact on downstream water quality and ecosystem function mediated by temporary stream surface connections.