Effects of iron limitation on carbon balance and photophysiology of the Antarctic diatom Chaetoceros cf. simplex

Bozzato Deborah; Jakob Torsten; Wilhelm Christian; Trimborn Scarlett

摘要

In the Southern Ocean (SO), iron (Fe) limitation strongly inhibits phytoplankton growth and generally decreases their primary productivity. Diatoms are a key component in the carbon (C) cycle, by taking up large amounts of anthropogenic CO2 through the biological carbon pump. In this study, we investigated the effects of Fe availability (no Fe and 4 nM FeCl3 addition) on the physiology of Chaetoceros cf. simplex, an ecologically relevant SO diatom. Our results are the first combining oxygen evolution and uptake rates with particulate organic carbon (POC) build up, pigments, photophysiological parameters and intracellular trace metal (TM) quotas in an Fe-deficient Antarctic diatom. Decreases in both oxygen evolution (through photosynthesis, P) and uptake (respiration, R) coincided with a lowered growth rate of Fe-deficient cells. In addition, cells displayed reduced electron transport rates (ETR) and chlorophyll a (Chla) content, resulting in reduced cellular POC formation. Interestingly, no differences were observed in non-photochemical quenching (NPQ) or in the ratio of gross photosynthesis to respiration (GP:R). Furthermore, TM quotas were measured, which represent an important and rarely quantified parameter in previous studies. Cellular quotas of manganese, zinc, cobalt and copper remained unchanged while Fe quotas of Fe-deficient cells were reduced by 60% compared with High Fe cells. Based on our data, Fe-deficient Chaetoceros cf. simplex cells were able to efficiently acclimate to low Fe conditions, reducing their intracellular Fe concentrations, the number of functional reaction centers of photosystem II (RCII) and photosynthetic rates, thus avoiding light absorption rather than dissipating the energy through NPQ. Our results demonstrate how Chaetoceros cf. simplex can adapt their physiology to lowered assimilatory metabolism by decreasing respiratory losses.

机译：在南海（SO）中，铁（Fe）限制强烈抑制浮游植物的生长，并且通常降低其初级生产率。硅藻是碳（c）循环中的关键组分，通过通过生物碳泵占据大量的人为二氧化碳。在这项研究中，我们研究了Fe可用性（NO FE和4 NM FECL3添加）对Chaetoceros CF的生理学的影响。 Simplex，一种生态相关所以硅藻。我们的研究结果是Fe缺陷南极硅藻中的第一种将颗粒有机碳（POC）含有颗粒有机碳（POC）的氧气进化和摄取率和摄取率。氧气进化（通过光合作用，P）和摄取（呼吸，r）均匀地减少，与Fe缺陷细胞的降低的生长速率一致。此外，细胞显示出电子传输速率（ETR）和叶绿素A（CHLA）含量，导致细胞POC形成降低。有趣的是，在非光化学猝灭（NPQ）中没有观察到差异或以呼吸毛毛毛的比例（GP：R）。此外，测量TM配额，其代表先前研究中的重要且很少量化的参数。锰，锌，钴和铜的细胞配额保持不变，而Fe缺陷细胞的Fe配额与高Fe细胞相比减少了60％。基于我们的数据，FE缺陷Chaetoceros CF.单纯x细胞能够有效地适应低Fe条件，降低它们的细胞内Fe浓度，照相系统II（RCII）和光合速率的功能反应中心的数量，从而避免光吸收而不是通过NPQ散发能量。我们的结果展示了如何Chaetoceros CF. Simplex可以通过降低呼吸损失来调整其生理学以降低同化代谢。

Effects of iron limitation on carbon balance and photophysiology of the Antarctic diatom Chaetoceros cf. simplex

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