Maberly Stephen Christopher, Stott Andrew W, Gontero Brigitte
UK Centre for Ecology & Hydrology, Lancaster Environment Centre, Lancaster, United Kingdom.
Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, Marseille, France.
Front Plant Sci. 2022 Sep 29;13:936716. doi: 10.3389/fpls.2022.936716. eCollection 2022.
Seagrass meadows are one of the most productive ecosystems on the planet, but their photosynthesis rate may be limited by carbon dioxide but mitigated by exploiting the high concentration of bicarbonate in the ocean using different active processes. Seagrasses are declining worldwide at an accelerating rate because of numerous anthropogenic pressures. However, rising ocean concentrations of dissolved inorganic carbon, caused by increases in atmospheric carbon dioxide, may benefit seagrass photosynthesis. Here we compare the ability of two seagrass from the Mediterranean Sea, (L.) Delile and L., to use carbon dioxide and bicarbonate at light saturation, and model how increasing concentrations of inorganic carbon affect their photosynthesis rate. pH-drift measurements confirmed that both species were able to use bicarbonate in addition to carbon dioxide, but that was more effective than . Kinetic experiments showed that, compared to , had a seven-fold higher affinity for carbon dioxide and a 1.6-fold higher affinity for bicarbonate. However, the maximal rate of bicarbonate uptake in was 2.1-fold higher than in . In equilibrium with 410 ppm carbon dioxide in the atmosphere, the modelled rates of photosynthesis by were slightly higher than , less carbon limited and depended on bicarbonate to a greater extent. This greater reliance by is consistent with its less depleted C content compared to . Modelled photosynthesis suggests that both species would depend on bicarbonate alone at an atmospheric carbon dioxide partial pressure of 280 ppm. was projected to benefit more than with increasing atmospheric carbon dioxide partial pressures, and at the highest carbon dioxide scenario of 1135 ppm, would have higher rates of photosynthesis and be more saturated by inorganic carbon than . In both species, the proportional reliance on bicarbonate declined markedly as carbon dioxide concentrations increased and in carbon dioxide would become the major source of inorganic carbon.
海草草甸是地球上生产力最高的生态系统之一，但其光合作用速率可能受到二氧化碳的限制，但通过利用不同的活跃过程利用海洋中高浓度的碳酸氢盐可缓解这一限制。由于众多人为压力，全球海草正以加速的速度减少。然而，大气中二氧化碳增加导致海洋中溶解无机碳浓度上升，这可能有利于海草的光合作用。在此，我们比较了两种来自地中海的海草，即（L.）德利尔海草和L.海草在光饱和时利用二氧化碳和碳酸氢盐的能力，并模拟了无机碳浓度增加如何影响它们的光合作用速率。pH漂移测量证实，这两个物种除了能利用二氧化碳外还能利用碳酸氢盐，但（此处原文缺失具体物种比较信息，无法准确翻译完整）比（此处原文缺失具体物种比较信息，无法准确翻译完整）更有效。动力学实验表明，与（此处原文缺失具体物种比较信息，无法准确翻译完整）相比，（此处原文缺失具体物种比较信息，无法准确翻译完整）对二氧化碳的亲和力高7倍，对碳酸氢盐的亲和力高1.6倍。然而，（此处原文缺失具体物种比较信息，无法准确翻译完整）中碳酸氢盐吸收的最大速率比（此处原文缺失具体物种比较信息，无法准确翻译完整）高2.1倍。在与大气中410 ppm二氧化碳达到平衡时，（此处原文缺失具体物种比较信息，无法准确翻译完整）模拟的光合作用速率略高于（此处原文缺失具体物种比较信息，无法准确翻译完整），受碳限制程度较低，且在更大程度上依赖碳酸氢盐。与（此处原文缺失具体物种比较信息，无法准确翻译完整）相比，（此处原文缺失具体物种比较信息，无法准确翻译完整）对碳酸氢盐的这种更大依赖与其C含量较少的消耗一致。模拟的光合作用表明，在大气二氧化碳分压为280 ppm时，这两个物种都将仅依赖碳酸氢盐。预计随着大气二氧化碳分压增加，（此处原文缺失具体物种比较信息，无法准确翻译完整）将比（此处原文缺失具体物种比较信息，无法准确翻译完整）受益更多，在最高二氧化碳情景1135 ppm下，（此处原文缺失具体物种比较信息，无法准确翻译完整）的光合作用速率将更高，且比（此处原文缺失具体物种比较信息，无法准确翻译完整）更易被无机碳饱和。在这两个物种中，随着二氧化碳浓度增加，对碳酸氢盐的比例依赖显著下降，并且在（此处原文缺失具体物种比较信息，无法准确翻译完整）中二氧化碳将成为无机碳的主要来源。
