Iron availability, cellular iron quotas, and nitrogen fixation in Trichodesmium
Iron availability, cellular iron quotas, and nitrogen fixation in Trichodesmium
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DOI：
10.4319/lo.2001.46.6.1249
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发表时间：
2001-09-01
影响因子：
4.5
通讯作者：
Falkowski, PG
中科院分区：
文献类型：
--
作者：
Berman-Frank, I;Cullen, JT;Falkowski, PG
铁的有效性被认为是限制海洋固氮的主要因素。这一假设主要基于对优势固氮蓝藻Trichodesmiun spp.在当代海洋中。虽然以前的研究与束毛藻表明，铁的可用性提高固氮和光合作用，没有明确的关系，细胞铁配额和固氮。我们重新研究了拟议的联系，铁的可用性和固氮在实验室隔离和自然种群收集沿海沃茨澳大利亚北部。在铁限制条件下生长的实验室培养物中，我们测量了细胞铁配额，光化学量子产率，光系统I到光系统II反应中心的相对丰度和固氮率的下降。固氮作用的临界阈值为Ca. log[Fe '] =-9.7。田间种群的束毛藻，收集在开花条件下，表现出高的铁配额与高固氮率相一致。利用风成铁通量的季节图和模型导出的地表水总溶解铁图，我们计算了全球海洋中束毛藻固氮的潜力。我们的研究结果表明，在全球75%的海洋中，铁的可用性限制了这种生物的固氮作用。鉴于目前的趋势，在水文循环中，我们认为，铁通量将在康宁世纪更加有限。
Iron availability is suggested to be a primary factor limiting nitrogen fixation in the oceans. This hypothesis is principally based on cost-benefit analyses of iron quotas in the dominant nitrogen-fixing cyanobacteria, Trichodesmiun spp., in the contemporary oceans. Although previous studies with Trichodesmium have indicated that iron availability enhanced nitrogen fixation and photosynthesis, no clear relationship has been reported between cellular iron quotas and nitrogen fixation. We re-examined the proposed link, between iron availability and nitrogen fixation in laboratory isolates and natural populations collected from coastal waters north of Australia. In laboratory cultures grown under iron-limiting conditions, we measured a decline in cellular iron quotas, photochemical quantum yields, the relative abundance of photosystem I to photosystem II reaction centers, and rates of nitrogen fixation. Nitrogen fixation displayed a critical threshold of the dissolved sum of total inorganic Fe species ([Fe ']) of ca. log[Fe '] = -9.7. Field populations of Trichodesmium, collected during bloom conditions, showed high iron quotas consistent with high nitrogen fixation rates. Using seasonal maps of aeolian iron fluxes and model-derived maps of surface water total dissolved Fe, we calculated the potential of nitrogen fixation by Trichodesmium in the global ocean. Our results suggest that in 75% of the global ocean, iron availability limits nitrogen fixation by this organism. Given present trends in the hydrological cycle, we suggest that iron fluxes will be even more limiting in the corning century.