Permafrost thawing mobilizes large quantities of organic carbon that was sequestered in Arctic regions over the last glacial cycle. Processes involved in the oxidation of this carbon need to be further assessed to estimate the fraction to be released into the atmosphere. Shallow tundra ponds are sites of active carbon turnover on the landscape and significant sources of greenhouse gases. Dissolved organic matter (DOM) leached from thawing peat into these ponds is exposed to sunlight, with the potential to accelerate its mineralization directly into CO₂ or through the production of more labile molecules. We tested the catalytic effect of sunlight on DOM mineralization in tundra ponds formed on organic‐rich polygonal landscapes originating from syngenetic permafrost, including a pond exposed to active permafrost erosion. Microbial decay rates, measured as the loss of chromophoric DOM, were similar to photodecay rates (1%–3% d⁻¹). Groups of fluorescing molecules were formed through microbial transformation or lost through photolysis at differing rates among studied ponds, with the erosive trough pond presenting a unique response suggesting the involvement of soil microbes. Despite the stimulation of microbial growth under sunlight and the dynamic response of DOM optical properties, the loss of dissolved organic carbon was not significant under any treatment. This suggests that microbial and photochemical mineralization of DOM was slow and potentially substrate‐limited during the dry period when ponds were sampled. The static nature of tundra ponds, with their long water retention time, may thus constrain hot moments when water moves and transports carbon on the landscape.

中文翻译：

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尽管对北极东部冻原池塘中的溶解有机物进行了强大的处理，但矿化却微弱

多年冻土融化动员了上个冰川周期中隔离在北极地区的大量有机碳。需要进一步评估与该碳的氧化有关的过程，以估计释放到大气中的比例。浅苔原池塘是景观中活性碳周转的场所，也是温室气体的重要来源。从解冻泥炭中浸出的溶解有机物（DOM）暴露在这些阳光下，有可能直接加速其矿化成CO ₂的潜力。或通过产生更不稳定的分子。我们测试了日光对苔原池塘中DOM矿化的催化作用，这些苔原池塘是由同生多年冻土形成的富含有机物的多边形地貌形成的，包括暴露于活跃多年冻土侵蚀的池塘。以发色DOM的损失来衡量的微生物衰减率与光衰减率相似（1％–3％d ^-1）。在研究的池塘之间，通过微生物转化形成的荧光分子组或通过光解以不同的速率丢失的分子，而侵蚀性槽池塘表现出独特的响应，表明土壤微生物参与其中。尽管刺激了阳光下微生物的生长和DOM光学特性的动态响应，但在任何处理下溶解有机碳的损失均不明显。这表明在池塘采样的干燥期间，DOM的微生物和光化学矿化作用很慢，并且可能受底物限制。苔原池塘的静态性质以及较长的保水时间可能会限制水在景观上移动和运输碳时的高温。