River flow intermittency affects physical and biological processes in lotic ecosystems, including nutrient attenuation and therefore water purification. We investigated the effect of river flow intermittency, including its duration and occurrence frequency, on the attenuation of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (P-PO₄³⁻). The net balances of each nutrient form were assessed in artificial streams colonized by biofilms and exposed to six treatments resulting from the combination of two flow intermittency durations (28 or 56 days) and three intermittency frequencies (one, two or four interruption episodes). The respective influences on the nutrient balances were assessed one and eight days after flow resumption, with negative or positive balances indicating net consumption or production, respectively. The P-PO₄³⁻ balances ranged from −50.3 to −15.7 μg P-PO₄³⁻ h⁻¹ m⁻², while for the components of DIN, they varied between −135.6 and −7.3 μg N-NH₄⁺ h⁻¹ m⁻² (ammonium), −1.4 and 4.2 μg N-NO₂⁻ h⁻¹ m⁻² (nitrite) and −39.1 and 18.6 μg N-NO₃⁻ h⁻¹ m⁻² (nitrate). In general, longer non-flow durations impaired nutrient attenuation. Overall, while each nutrient form showed specific patterns, our experiment indicated that (1) nutrient attenuation usually decreased with longer non-flow durations, (2) attenuation generally recovered after frequent events of water flow resumption and when rewetting was longer and (3) longer desiccation periods seemed to persistently affect the biogeochemical responses regardless the number of times flow returned to the system. Our results highlight that more severe conditions (causing dehydration of the substrates and inhibition of biofilm activity) might strongly affect the biogeochemical functioning of temporary streams, with important management implications under accelerating global changes.

中文翻译：

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营养流衰减会因流动间歇的持续时间和频率而改变

河流流动的间歇性影响流动生态系统中的物理和生物过程，包括养分衰减和水净化。我们研究了河流流动间歇性对溶解无机氮 (DIN) 和可溶性活性磷 (P-PO ₄ ^{3− ) 衰减的影响，包括其持续时间和发生频率}）。每种营养形式的净平衡在由生物膜定殖的人工溪流中进行评估，并暴露于由两种流动间歇持续时间（28 或 56 天）和三种间歇频率（一次、两次或四次中断发作）组合产生的六次处理。在流量恢复后 1 天和 8 天评估各自对养分平衡的影响，负平衡或正平衡分别表示净消耗或生产。P-PO ₄ ^3-平衡范围为-50.3 至-15.7 μg P-PO ₄ ^3- h ^-1  m ^-2，而对于DIN 的组分，它们在-135.6 和-7.3 μg N-NH ₄ ⁺之间变化h ^-1 米^-2（铵）、-1.4 和 4.2 μg N-NO ₂ ^- h ^-1  m ^-2（亚硝酸盐）和 -39.1 和 18.6 μg N-NO ₃ ^- h ^-1  m ^-2（硝酸盐）。一般来说，较长的非流动持续时间会损害营养衰减。总体而言，虽然每种养分形式都显示出特定的模式，但我们的实验表明（1）养分衰减通常随着非流动持续时间的延长而降低，（2）在水流恢复频繁事件和再润湿时间更长时衰减通常会恢复（3）无论流量返回系统的次数如何，较长的干燥期似乎都会持续影响生物地球化学反应。我们的研究结果强调，更严重的条件（导致底物脱水和生物膜活性抑制）可能强烈影响临时河流的生物地球化学功能，在全球加速变化下具有重要的管理意义。