Estimates of primary productivity have traditionally disregarded dark inorganic carbon fixation by marine microorganisms. Currently, only limited data are available from different systems on this potentially ecologically important process. We present monthly dark inorganic carbon fixation and photosynthetic rates from the euphotic layer of the northern Gulf of Aqaba collected over a decade between 2010 and 2020. Averaged dark inorganic carbon fixation rates from surface to 100 m depth, ranged from 99 to 173 mg C m−2 d−1, which corresponds to ~ 43% of the annual primary productivity at this location. The lowest dark inorganic carbon fixation rates were found during winter, contributing ~ 7.5% of the integrated primary productivity. During the oligotrophic summer, dark inorganic carbon fixation comprised a larger fraction of the integrated primary productivity estimated as ~ 12%. In accordance, dark inorganic carbon fixation contributed ~ 6% to the particulate organic carbon flux during the winter and ~ 30% during summertime. Complimentary nutrient‐enrichment bioassays of seawater from 5 m show that dissolved organic nutrient enrichment (P and C based) significantly elevates dark inorganic carbon fixation, whereas addition of dissolved inorganic nutrients (, , or both) significantly increased photosynthesis but to a lesser extent dark inorganic carbon fixation. These results suggest that dark inorganic carbon fixation may be an important biochemical process throughout the euphotic zone of oligotrophic seas, and thus should be incorporated into oceanic carbon production estimates.

中文翻译：

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贫营养海富光带中显着的暗无机碳固定

对初级生产力的估计传统上忽略了海洋微生物的暗无机碳固定。目前，关于这一潜在的生态重要过程，来自不同系统的数据有限。我们提供了 2010 年至 2020 年间收集的亚喀巴湾北部透光层的月度暗无机碳固定率和光合速率。从表面到 100 m 深度的平均暗无机碳固定率范围为 99 至 173 mg C m−2d−1，相当于该地点年初级生产力的约 43%。冬季深色无机碳固定率最低，约占综合初级生产力的 7.5%。在贫营养夏季，深色无机碳固定占综合初级生产力的较大部分，估计约为 12%。因此，深色无机碳固定在冬季对颗粒有机碳通量贡献约 6%，在夏季贡献约 30%。对 5 m 海水的补充营养物富集生物测定表明，溶解的有机营养物富集（基于 P 和 C）显着提高了暗无机碳固定，而添加溶解的无机营养物（、 或两者）显着增加了光合作用，但在较小程度上增加了暗无机碳固定。无机碳固定。这些结果表明，暗无机碳固定可能是整个贫营养海洋富光带的重要生化过程，因此应纳入海洋碳生产估算。