Gradient-dominated ecosystems: sources and regulatory functions of dissolved organic matter in freshwater ecosystems
Gradient-dominated ecosystems: sources and regulatory functions of dissolved organic matter in freshwater ecosystems
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DOI：
10.1007/bf00007000
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发表时间：
1992-02
期刊：
影响因子：
2.6
通讯作者：
R. Wetzel
中科院分区：
文献类型：
--
作者：
R. Wetzel
陆地-水域带的紧急湿地和沿岸的组成部分在功能上通过溶解的有机物的数量和类型耦合，所述溶解的有机物被释放、加工、运输到接收沃茨，然后在接收水域内进一步加工。淡水生态系统中的操作耦合和整合发生在从微米到千米尺度的若干尺度上的沿着物理和代谢梯度。湖泊和河流生态系统中的溶解有机碳（DOC）主要来源于高等植物和沉积物碎屑微生物的光合作用，而微生物群落的运转和周转是沿着大尺度梯度物质通量的代谢基础。只有通过浮游植物的光合作用才能增加。当湿地和沿岸的界面区产生的溶解性有机化合物向生态系统的开放水域移动时，部分利用会影响有机溶解性的选择性增加。即使DOC从外来的和界面源是更多的arbitricitrant比所产生的浮游微生物区系，分解的更大的界面量进口到远洋区dominatesecosystem分解。观察到的高持续生产力的土地-水界面区的结果，从广泛的回收利用的基本资源（养分，无机碳）和保护机制。平均而言，在湖泊和溪流中，超过90%的生态系统分解是由细菌利用来自非浮游生物初级生产力来源的DOM进行的。除了直接矿化的DOC从非远洋来源，许多有机化合物的功能间接影响新陈代谢。提出了腐植酸和富里酸与胞外酶形成复合物的新证据。这些复合物抑制酶的活性，并可以在生态系统内运输。该复合物可以通过温和的紫外光分解与再生的酶活性在移位的位置解耦。
The emergent wetland and littoral components of the land-water zone are functionally coupled by the amounts and types of dissolved organic matter that are released, processed, transported to, and then further processed within the recipient waters. Operational couplings and integrations in freshwater ecosystems occur along physical and metabolic gradients of a number of scales from micrometer to kilometer dimensions. The operation and turnover of the microbial communities, largely associated with surfaces, generate the metabolic foundations for material fluxes along larger-scale gradients.Because of the predominance of small, shallow freshwater bodies, most dissolved organic carbon (DOC) of lacustrine and riverine ecosystems is derived from photosynthesis of higher plants and microflora associated with detritus, including sediments, and is only augmented by photosynthesis of phytoplankton. As the dissolved organic compounds generated in the wetland and littoral interface regions move toward the open-water regions of the ecosystems, partial utilization effects a selective increase in organic recalcitrance. Even though DOC from allochthonous and from interface sources is more recalcitrant than that produced by planktonic microflora, decomposition of the much larger interface quantities imported to the pelagic zone dominatesecosystemdecomposition. The observed high sustained productivity of the land-water interface zone results from extensive recycling of essential resources (nutrients, inorganic carbon) and conservation mechanisms. On the average in lakes and streams, greater than 90 percent of the decomposition in theecosystemis by bacteria utilizing DOM from non-pelagic sources of primary productivity. In addition to direct mineralization of DOC from non-pelagic sources, many of the organic compounds function indirectly to influence metabolism. New evidence is presented to demonstrate formation of complexes between humic and fulvic organic acids and extracellular enzymes. These complexes inhibit enzyme activity and can be transported within the ecosystem. The complex can be decoupled by mild ultraviolet photolysis with regeneration of enzyme activity in displaced locations.