Dellisanti Walter, Zhang Qingfeng, Ferrier-Pagès Christine, Kühl Michael
Department of Biology, Marine Biology Section, University of Copenhagen, Helsingør, Denmark.
Coral Ecophysiology Laboratory, Center Scientifique de Monaco, Principality of Monaco, Monaco.
PeerJ. 2024 Apr 29;12:e17259. doi: 10.7717/peerj.17259. eCollection 2024.
Iron (Fe) plays a fundamental role in coral symbiosis, supporting photosynthesis, respiration, and many important enzymatic reactions. However, the extent to which corals are limited by Fe and their metabolic responses to inorganic Fe enrichment remains to be understood. We used respirometry, variable chlorophyll fluorescence, and O microsensors to investigate the impact of increasing Fe(III) concentrations (20, 50, and 100 nM) on the photosynthetic capacity of two Mediterranean coral species, and . While the bioavailability of inorganic Fe can rapidly decrease, we nevertheless observed significant physiological effects at all Fe concentrations. In , exposure to 50 nM Fe(III) increased rates of respiration and photosynthesis, while the relative electron transport rate (rETR(II)) decreased at higher Fe(III) exposure (100 nM). In contrast, reduced respiration, photosynthesis rates, and maximum PSII quantum yield (F/F) across all iron enrichments. Both corals exhibited increased hypoxia (<50 µmol O L) within their gastric cavity at night when exposed to 50 and 100 nM Fe(III), leading to increased polyp contraction time and reduced O exchange with the surrounding water. Our results indicate that , but not , might be limited in Fe for achieving maximal photosynthetic efficiency. Understanding the multifaceted role of iron in corals' health and their response to environmental change is crucial for effective coral conservation.
铁（Fe）在珊瑚共生中起着至关重要的作用，支持光合作用、呼吸作用以及许多重要的酶促反应。然而，珊瑚受铁限制的程度以及它们对无机铁富集的代谢反应仍有待了解。我们使用呼吸测定法、可变叶绿素荧光法和氧微传感器来研究增加铁（III）浓度（20、50和100纳摩尔）对两种地中海珊瑚物种[珊瑚物种名称1]和[珊瑚物种名称2]光合能力的影响。虽然无机铁的生物利用度可能会迅速降低，但我们仍观察到在所有铁浓度下都有显著的生理效应。在[珊瑚物种名称1]中，暴露于50纳摩尔铁（III）会增加呼吸和光合作用速率，而在更高的铁（III）暴露水平（100纳摩尔）下相对电子传递速率（rETR(II)）会降低。相比之下，[珊瑚物种名称2]在所有铁富集情况下，呼吸、光合作用速率和最大PSII量子产率（F/Fm）均降低。当暴露于50和100纳摩尔铁（III）时，两种珊瑚在夜间胃腔内的缺氧情况（<50微摩尔O₂/升）都会增加，导致息肉收缩时间增加，与周围水的氧交换减少。我们的结果表明，[珊瑚物种名称1]而非[珊瑚物种名称2]在铁含量方面可能受到限制，无法实现最大光合效率。了解铁在珊瑚健康中的多方面作用及其对环境变化的反应对于有效的珊瑚保护至关重要。
