Aquatic primary productivity produces oxygen (O₂) and consumes carbon dioxide (CO₂) in a ratio of ~1.2. However, in aquatic ecosystems, dissolved CO₂ concentrations can be low, potentially limiting primary productivity. Here, results show that a large drainage basin maintains its highest levels of gross primary productivity (GPP) when dissolved CO₂ is diminished or undetectable due to photosynthetic uptake. Data show that, after CO₂ is depleted, bicarbonate, an ionized form of inorganic carbon, supports these high levels of productivity. In fact, outputs from a process-based model suggest that bicarbonate can support up to ~58% of GPP under the most productive conditions. This is the first evidence that high levels of aquatic GPP are sustained in a riverine drainage network despite CO₂ depletion, which has implications for freshwater ecology, biogeochemistry, and isotopic analysis.

中文翻译：

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尽管温带河流网络中的二氧化碳消耗殆尽，但仍保持了最高的总初级生产力

水生初级生产力产生氧气 (O ₂ ) 并消耗二氧化碳 (CO ₂ )，比例约为 1.2。然而，在水生生态系统中，溶解的 CO ₂浓度可能很低，这可能会限制初级生产力。在这里，结果表明，当溶解的 CO ₂由于光合吸收而减少或无法检测时，大型流域保持其最高水平的总初级生产力 (GPP) 。数据表明，经过 CO ₂被耗尽的碳酸氢盐，一种无机碳的离子化形式，支持这些高水平的生产力。事实上，基于过程的模型的输出表明，在最高效的条件下，碳酸氢盐可支持高达约 58% 的 GPP。这是第一个证据表明，尽管 CO ₂耗尽，但河流排水网络中仍维持高水平的水生 GPP ，这对淡水生态、生物地球化学和同位素分析具有影响。