Land cover and nutrient enrichment regulates low-molecular weight dissolved organic matter turnover in freshwater ecosystems
Land cover and nutrient enrichment regulates low-molecular weight dissolved organic matter turnover in freshwater ecosystems
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DOI：
10.1002/lno.11852
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发表时间：
2021-06-01
影响因子：
4.5
通讯作者：
Jones, Davey L.
中科院分区：
文献类型：
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作者：
Brailsford, Francesca L.;Glanville, Helen C.;Jones, Davey L.
溶解有机物（DOM）是一种复杂的含碳化合物的混合物。低分子量（LMW）部分组成了数千种不同的化合物，并代表了很大比例的DOM在水生生态系统中。这种低分子量DOM的周转率可能非常高。由于在分子尺度上测量该池的挑战，相对而言，对LOTIC系统中LMW DOM化合物的命运知之甚少。本研究解决了这一知识差距，调查的微生物处理的低分子量DOM在45个网站，代表了一系列的理化梯度和占主导地位的土地覆盖在英国。利用放射性同位素示踪剂代表低分子量溶解性有机碳（DOC）（葡萄糖）、溶解性有机氮（DON）（氨基酸混合物）、溶解性有机磷（DOP）（葡萄糖-6-磷酸盐）和可溶性活性磷（SRP，以正磷酸盐计），测定了河流沃茨中不同DOM化合物的微生物吸收。DOM的生物降解量在不同组分之间存在差异（DON >= DOC > DOP），三者的周转率沿着N和P富集的梯度增加。相反地，SRP的摄取沿着该相同梯度沿着降低。这是由于优先利用DOP超过SRP。主要土地覆盖对DOM资源的利用有显著影响，因为它控制了集水区内的养分富集。我们的结论是，营养丰富的河流沃茨将导致进一步DOM从水体中去除，增加微生物的生长，并在流氧饱和度的下降，加剧了河流中的富营养化的影响。
Dissolved organic matter (DOM) is a complex mixture of carbon-containing compounds. The low-molecular weight (LMW) fraction constitutes thousands of different compounds and represents a substantial proportion of DOM in aquatic ecosystems. The turnover rates of this LMW DOM can be extremely high. Due to the challenges of measuring this pool at a molecular scale, comparatively little is known of the fate of LMW DOM compounds in lotic systems. This study addresses this knowledge gap, investigating the microbial processing of LMW DOM across 45 sites representing a range of physicochemical gradients and dominant land covers in the United Kingdom. Radioisotope tracers representing LMW dissolved organic carbon (DOC) (glucose), dissolved organic nitrogen (DON) (amino acid mixture), dissolved organic phosphorus (DOP) (glucose-6-phosphate), and soluble reactive phosphorus (SRP, measured as orthophosphate) were used to measure the microbial uptake of different DOM compounds in river waters. The amount of DOM biodegradation varied between different components (DON >= DOC > DOP), with the rate of turnover of all three increasing along a gradient of N and P enrichment across the range of sites. Conversely, the uptake of SRP decreased along this same gradient. This was ascribed to preferential utilization of DOP over SRP. Dominant land cover had a significant effect on DOM use as a resource, due to its control of nutrient enrichment within the catchments. We conclude that nutrient enrichment of river waters will lead to further DOM removal from the water column, increased microbial growth, and a decrease in stream oxygen saturation, exacerbating the effects of eutrophication in rivers.