Estuarine sediments make an important contribution to the global carbon cycle, but we do not know how this will change under a future climate, which is expected to have lower pH oceans and frequent high-temperature days. Six combinations of warming and partial pressures of CO₂ (pCO₂) were chosen to investigate the combined and individual effects of short-term pressures on the diel metabolic response of shallow unvegetated sediments ex-situ. Whereas warming significantly increased respiration, making sediments more heterotrophic, high-pCO₂ increased net primary productivity, resulting in less heterotrophic sediments. As a result, warming decreased the carbon burial potential of estuarine sediments and high-pCO₂ had the opposite effect. High-pCO₂ mitigates the negative effects of warming on benthic metabolism under the combined scenario, with carbon burial similar to that expected under high-pCO₂ conditions alone. Climate scenarios also changed the diurnal pCO₂ variation, with ranges increasing by 33% with warming, and almost doubling under high-pCO₂ conditions. An additive response in pCO₂ variability was observed under the combined scenario, increasing to 2.3× the current diel-pCO₂ range, highlighting the reduced buffering capacity of the water associated with a high CO₂ climate. Future carbon burial and export under increased frequencies of unseasonably warm days projected for mid and end of century (30% and 50% of days-per-year, respectively) were estimated with and without ocean acidification. By 2100, warming alone could decrease annual estuarine sediment burial potential by 25%. However, ocean acidification could mitigate the negative effects of more frequent high-temperature days and increase carbon burial potential over current conditions by ~18%.

中文翻译：

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海洋酸化可能会减轻变暖对潮下带无植被河口沉积物中碳埋藏潜力的负面影响

河口沉积物对全球碳循环做出了重要贡献，但我们不知道在未来的气候下这将如何变化，预计海洋 pH 值较低，高温天气频繁。选择变暖和 CO ₂分压( p CO ₂ ) 的六种组合来研究短期压力对浅层无植被沉积物异地代谢响应的组合和单独影响。变暖显着增加了呼吸作用，使沉积物更加异养，而高p CO ₂增加了净初级生产力，导致异养沉积物减少。结果，变暖降低了河口沉积物的碳埋藏潜力和高p CO ₂具有相反的效果。高p CO ₂在组合情景下减轻了变暖对底栖代谢的负面影响，碳埋藏类似于单独在高p CO ₂条件下的预期。气候情景也改变了昼夜p CO _{2 的}变化，随着变暖，变化范围增加了 33%，在高p CO ₂条件下几乎翻了一番。在组合情景下观察到p CO ₂变异性的附加响应，增加到当前柴油p CO _{2 的}2.3 倍范围，突出了与高 CO ₂气候相关的水的缓冲能力降低。预计在本世纪中叶和末期（分别为每年天数的 30% 和 50%），在有和没有海洋酸化的情况下，未来的碳埋藏和出口频率会增加。到 2100 年，仅气候变暖就会将河口沉积物的年埋藏潜力降低 25%。然而，海洋酸化可以减轻更频繁的高温日的负面影响，并使当前条件下的碳埋藏潜力增加约 18%。