Abstract Dissolved O2 (DO) concentration is critical to determining ecosystem functions such as organic matter respiration, which can favor fixed nitrogen loss and the accumulation of compounds such as NH4+. This dynamic is observed in central Chile's coastal upwelling system (36 °S), which presents seasonally O2 deficient waters and high biological productivity. Temporal dynamics for dissolved inorganic nitrogen (DIN: NO3−, NO2− and NH4+) are analyzed based on a ten year time series of monthly measurements of DO and DIN and a three year record of absolute DIN uptake rates (ρDIN), respective turnover rates (νDIN), and O2 utilization rates (OUR). Observed O2 deficit gradually increases from hypoxia to near anoxia as the system becomes more productive, favoring the accumulation of NO2− and NH4+. Three temporal phases within the aphotic layer were distinguished: (I) DO > 62 μmol L−1 (May to August), (II) 5 820 days). Integrated OUR gradually increased from phase I to III (from 225 to 422 mmol m−2 d−1), with DO pools replenished over 2.3 to 26 days. NH4+ regeneration rates ranged from 34 to 62 mmol m−2 d−1 and NH4+ pools were replenished within a few days. Variation in DO, which regulates N cycling, may explain the accumulation of N-species within the aphotic layer. Observed trends could be extrapolated to scenarios of upwelling-favorable winds, eutrophication and hypoxia.

中文翻译：

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具有可变溶解氧的沿海上升流系统的无光层中溶解无机氮 (DIN) 的时间动态

摘要 溶解氧 (DO) 浓度对于确定生态系统功能（如有机物质呼吸）至关重要，这有利于固定氮损失和化合物（如 NH4+）的积累。在智利中部沿海上升流系统 (36 °S) 中观察到这种动态，该系统呈现季节性缺氧水域和高生物生产力。溶解无机氮（DIN：NO3−、NO2− 和 NH4+）的时间动态基于 DO 和 DIN 每月测量值的十年时间序列以及绝对 DIN 吸收率 (ρDIN) 和相应周转率的三年记录进行分析(νDIN) 和 O2 利用率 (OUR)。随着系统变得更有生产力，观察到的 O2 缺乏逐渐从缺氧增加到接近缺氧，有利于 NO2- 和 NH4+ 的积累。区分无光层内的三个时间阶段：（I）DO > 62 μmol L-1（5 月至 8 月），（II）5 820 天。综合 OUR 从第一阶段逐渐增加到第三阶段（从 225 到 422 mmol m-2 d-1），溶解氧池在 2.3 到 26 天内得到补充。NH4+ 再生率范围为 34 到 62 mmol m-2 d-1，并且在几天内补充了 NH4+ 池。调节 N 循环的 DO 的变化可以解释无光层内 N 物种的积累。观察到的趋势可以外推到有利于上升流的风、富营养化和缺氧的情景。NH4+ 再生率范围为 34 到 62 mmol m-2 d-1，并且在几天内补充了 NH4+ 池。调节 N 循环的 DO 的变化可以解释无光层内 N 物种的积累。观察到的趋势可以外推到有利于上升流的风、富营养化和缺氧的情景。NH4+ 再生率范围为 34 到 62 mmol m-2 d-1，并且在几天内补充了 NH4+ 池。调节 N 循环的 DO 的变化可以解释无光层内 N 物种的积累。观察到的趋势可以外推到有利于上升流的风、富营养化和缺氧的情景。