Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28‐day incubations. We incubated late‐summer stream water from 23 locations nested in seven northern or high‐altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two‐way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways.

中文翻译：

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永久冻土地区溪流溶解的有机物显示出令人惊讶的成分相似性，但具有负面启动和营养效应


永久冻土退化正在向地表水网络输送生物可利用的溶解有机物 (DOM) 和无机营养物质。虽然这些永久冻土补贴仅占河流 DOM 和养分通量总量的一小部分，但它们可能通过破坏背景 DOM 稳定的启动效应或养分效应，影响食物网和净生态系统碳平衡。我们研究了添加生物不稳定碳（乙酸盐）和无机营养物（氮和磷）如何影响 DOM 分解（28 天的培养）。我们培育了来自亚洲、欧洲和北美七个北部或高海拔地区 23 个地点的夏末溪流水。 DOM 损失范围为 3% 至 52%，显示流网络内的各种纵向模式。 DOM 光学性质差异很大，但基于傅里叶变换离子回旋共振质谱 (FT-ICR MS) 分析，DOM 显示出成分相似性。醋酸盐和营养物质的添加降低了本体 DOM 矿化（即负启动），对可生物降解的 DOM 产生更多负面影响，但对稳定 DOM 产生中性或正面影响。出乎意料的是，醋酸盐和营养物质引发了有色 DOM (CDOM) 的分解，对照组中值下降了 1.6%，修正处理中下降了 22%。此外，添加乙酸盐的吸收受到各个地点营养物质可用性的强烈限制。这些发现表明，生物不稳定的 DOM 和从退化的永久冻土中释放的营养物质可能会降低背景 DOM 矿化，但会改变接收水体的化学计量和光照条件。 我们得出的结论是，在北部水生生态系统中，启动效应和营养效应是耦合的，量化 DOM 特性和环境条件之间的双向相互作用可以解决关于永久冻土区水道 DOM 驱动因素的相互矛盾的观察结果。