Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton
Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton
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DOI：
10.1016/j.marchem.2014.10.002
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发表时间：
2015-07-20
期刊：
影响因子：
3
通讯作者：
Doblin, Martina A.
中科院分区：
文献类型：
--
作者：
Hassler, Christel S.;Norman, Louiza;Doblin, Martina A.
由于缺乏铁，海洋藻类的生长受到限制，这发生在全球40%的海洋中。尽管有机化合物对铁地球化学的影响取得了重要进展，但它们在控制原核和真核浮游植物铁可用性方面的作用仍不清楚。藻类和细菌的胞外聚合物（EPS）是否包含有助于铁限制性浮游植物生长的有机配体仍然是一个未知数。如果是这样的话，那么EPS可以减轻浮游植物的铁限制与生物碳泵的影响，从而调节大气中的CO2。在这里，我们比较了藻类，细菌和原位EPS与模型化合物，铁载体和两个生物参数，包括铁的生物利用度，浮游植物生长，光生理和群落结构的生物影响。实验室和现场实验表明，海洋微生物产生的EPS在维持生物铁吸收以及藻类生长方面是有效的，并且可以影响天然浮游植物群落结构。我们的数据表明，在EPS的存在下，自然浮游植物的生长增强不仅是由于高生物可利用的铁的形式，而且还因为EPS含有其他微量营养素。在铁-铁载体富集后检测到较强的配体（log K-Fe ′ L = 12.0），并且在EPS存在下测量较弱的配体（log K-Fe ′ L = 10.4-11.0）。在我们的四天孵育期间，有机配体的条件稳定常数的趋势似乎不受生物活性和光化学的影响。在我们的野外实验中观察到的浮游植物群落的变化在不同地点之间并没有均匀地观察到，这使得很难推断哪些官能团将从与EPS结合的铁中获益最多。(C)2014爱思唯尔有限公司版权所有。
Growth limitation of marine algae due to lack of iron occurs in up to 40% of the global ocean. Despite important advances on the impact of organic compounds on iron biogeochemistry, their roles in controlling iron availability to prokaryotic and eukaryotic phytoplankton remain unclear. Whether algal and bacterial exopolymeric substances (EPS) include organic ligands which may help iron-limited phytoplankton growth remains an unknown. If so, then EPS could relieve phytoplankton iron limitation with implications for the biological carbon pump and hence the regulation of atmospheric CO2. Here we compared the biological impact of algal, bacterial and in situ EPS with model compounds, a siderophore and two saccharides on biological parameters including, iron bioavailability, phytoplankton growth, photo-physiology and community structure. Laboratory and field experiments demonstrated that EPS produced by marine microorganisms are efficient in sustaining biological iron uptake as well as algal growth, and can affect natural phytoplankton community structure. Our data suggest that natural phytoplankton growth enhancement in the presence of EPS was not solely due to highly bioavailable iron forms, but also because EPS contains other micronutrients. Stronger ligands were detected following iron-siderophore enrichments (log K-Fe'L = 12.0) and weaker ligands were measured in the presence of EPS (log K-Fe'L = 10.4-11.0). The trend of the conditional stability constants of organic ligands did not seem to be affected as a result of biological activity and photo-chemistry during our four day incubations. The shift in the phytoplankton community observed during our field experiments was not uniformly observed between different sites rendering it difficult to extrapolate which functional group(s) would benefit the most from iron bound to EPS. (C) 2014 Elsevier B.V. All rights reserved.