Aluminum (Al) may play a role in the ocean's capacity for absorbing atmospheric CO2 via influencing carbon fixation, export, and sequestration. Aluminum fertilization, especially in iron (Fe)‐limited high‐nutrient, low‐chlorophyll ocean regions, has been proposed as a potential CO2 removal strategy to mitigate global warming. However, how Al addition would influence the solubility and bioavailability of Fe as well as the physiology of Fe‐limited phytoplankton has not yet been examined. Here, we show that Al addition (20 and 100 nM) had little influence on the Fe solubility in surface seawater and decreased the Fe bio‐uptake by 11–22% in Fe‐limited diatom Thalassiosira weissflogii in Fe‐buffered media. On the other hand, the Al addition significantly increased the rate of chlorophyll biosynthesis by 45–60% for Fe‐limited T. weissflogii and 81–102% for Fe‐limited Thalassiosira pseudonana, as well as their cell size, cellular chlorophyll content, photosynthetic quantum efficiency (Fv/Fm) and growth rate. Under Fe‐sufficient conditions, the Al addition still led to an increased growth rate, though the beneficial effects of Al addition on chlorophyll biosynthesis were no longer apparent. These results suggest that Al may facilitate chlorophyll biosynthesis and benefit the photosynthetic efficiency and growth of Fe‐limited diatoms. We speculate that Al addition may enhance intracellular Fe use efficiency for chlorophyll biosynthesis by facilitating the superoxide‐mediated intracellular reduction of Fe(III) to Fe(II). Our study provides new evidence and support for the iron–aluminum hypothesis.

中文翻译：

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添加铝对两种养殖限铁海洋硅藻叶绿素生物合成和生长的促进作用

铝 (Al) 可能在海洋吸收大气二氧化碳的能力中发挥作用2通过影响碳固定、出口和封存。铝施肥，特别是在铁（Fe）有限的高营养、低叶绿素海洋区域，已被提议作为潜在的二氧化碳2缓解全球变暖的清除策略。然而，Al的添加将如何影响Fe的溶解度和生物利用度以及Fe限制浮游植物的生理学尚未得到研究。在这里，我们表明添加 Al（20 和 100 nM）对表层海水中 Fe 的溶解度影响不大，并且使 Fe 限制硅藻的 Fe 生物吸收降低了 11-22%魏氏海链藻在 Fe 缓冲介质中。另一方面，对于 Fe 限制，Al 的添加显着提高了叶绿素生物合成率 45-60%魏斯弗洛木樨Fe 限制为 81–102%假微型海链藻，以及它们的细胞大小、细胞叶绿素含量、光合量子效率（Fv/F米）和增长率。在铁充足的条件下，添加铝仍然会导致生长速率增加，尽管添加铝对叶绿素生物合成的有益作用不再明显。这些结果表明，铝可能促进叶绿素生物合成，有利于铁限制硅藻的光合作用效率和生长。我们推测，添加 Al 可能通过促进超氧化物介导的细胞内 Fe(III) 还原为 Fe(II) 来提高叶绿素生物合成的细胞内 Fe 使用效率。我们的研究为铁铝假说提供了新的证据和支持。