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Biological lability of dissolved organic carbon in stream water and contributing terrestrial sources

机译：溪流水中溶解的有机碳的生物不稳定性和陆地来源

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Terrestrial sources of dissolved organic C (DOC) provide energy for stream microbial heterotrophs. Hydrologic conditions alter flow paths to the stream and influence terrestrial source quantity and quality. We used bioreactors to measure biodegradable DOC (BDOC) in water from soils, shallow wells, and spring seeps under baseflow conditions, overland flow during storms, and a stream during base flow and storm flow. Stream DOC concentrations ranged from 0.7 to 15.5 mg C/L and total BDOC ranged from 0.1 to 8.7 mg C/L. Under baseflow conditions, DOC was generally <2 mg C/L and BDOC was <0.7 mg C/L. BDOC made up 37.8% of DOC (8.2% labile and 29.6% semilabile constituents) and most DOC (62.2%) was recalcitrant. Storms increased DOC concentrations 6- to 12-fold and selectively mobilized BDOC increasing concentrations 8- to 27-fold. Labile and semilabile constituents increased 2-fold to 17.3% and 55.4%, respectively, so that storm flow DOC was largely biodegradable (73%). Terrestrial DOC concentrations declined from 2.15 mg C/L in soil water to 1.78 mg C/L in shallow wells to 1.26 mg C/L in spring seeps, and labile BDOC concentrations declined from 0.1 mg C/L in soil water to 0.04 mg C/L in shallow wells but increased to 0.13 mg C/L in spring seeps. Overland flow waters had elevated DOC (11.0 mg C/L) and labile BDOC (1.7 mg C/L) concentrations. Peak storm concentrations for 2 biological reactivity classes were coincident during 2 storms but divergent during another storm, suggesting temporal variation in hydrologic pathways. Our results demonstrate that storms deliver increased BDOC loads to a headwater stream and reveal the temporal variability of labile and semilabile BDOC constituents. Storms increase stream depth and velocity, resulting in increased uptake lengths for BDOC constituents, exporting them from the basin and probably providing a downstream subsidy.
机译：溶解有机碳（DOC）的陆地来源为流微生物异养生物提供能量。水文条件改变了河流的流动路径，并影响了陆源的数量和质量。我们使用生物反应器测量了基流条件下土壤，浅井和泉水中的水，暴风雨期间的陆上流量以及基流和暴风雨期间的水流中水中的可生物降解DOC（BDOC）。流DOC的浓度范围为0.7至15.5 mg C / L，总BDOC的浓度范围为0.1至8.7 mg C / L。在基流条件下，DOC通常<2 mg C / L，而BDOC <0.7 mg C / L。 BDOC占DOC的37.8％（不稳定的8.2％和半不稳定的29.6％），大多数DOC（62.2％）是顽强的。风暴使DOC浓度增加6至12倍，而选择性地动员BDOC使浓度增加8至27倍。不稳定和半不稳定成分分别增加了2倍，分别达到17.3％和55.4％，因此暴风雨DOC在很大程度上是可生物降解的（73％）。陆地DOC浓度从土壤水中的2.15 mg C / L降低到浅井的1.78 mg C / L，到春季渗水的1.26 mg C / L，不稳定的BDOC浓度从土壤水中的0.1 mg C / L降低到0.04 mg C / L / L在浅井中，但在春季渗漏中升至0.13 mg C / L。陆上流水的DOC（11.0 mg C / L）和BDOC（1.7 mg C / L）不稳定。 2种生物反应性类别的峰值暴风雨浓度在2次暴风雨中是一致的，但在另一次暴风雨中却有所不同，表明水文路径的时间变化。我们的结果表明，暴风雨将增加的BDOC负荷带至源头水流，并揭示了不稳定和半不稳定的BDOC成分的时间变异性。风暴增加了溪流的深度和速度，导致BDOC成分的吸收长度增加，将其从盆地中排出，并可能提供下游补贴。

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