Efficient recycling of nutrients in modern and past hypersaline environments
Efficient recycling of nutrients in modern and past hypersaline environments
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现代和过去的高盐环境中营养物质的有效回收
DOI：
10.1038/s41598-019-40174-9
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发表时间：
2019
影响因子：
4.6
通讯作者：
Ohkouchi N.
中科院分区：
文献类型：
--
作者：
Isaji Y.;Kawahata H.;Ogawa N. O.;Kuroda J.;Yoshimura T.;Jimenez-Espejo F. J.;Makabe A.;Shibuya T.;Lugli S.;Santulli A.;Manzi V.;Roveri M.;Ohkouchi N.
高盐度环境的生物地球化学受到生物过程和物理化学参数变化的强烈影响。尽管大规模蒸发事件在整个地球历史上反复发生，但它们的生物地球化学循环和全球影响仍然知之甚少。在这里，我们提供了来自现代浅层高盐度环境(意大利特拉帕尼的太阳盐湖)营养物质和氯色素的第一个氮同位素数据，并将所获得的见解应用于中新世晚期梅西尼亚盐度危机的δ15N特征。底栖生物垫中叶绿素、细菌叶绿素、硝酸盐和氨氮的浓度和δ15N表明，硝化作用的抑制抑制了反硝化和厌氧氨氧化，导致了氨氮在底栖微生物垫内的有效循环和高的初级生产力。我们还认为，随着盐度的增加，贫化15N的NH3(气体)的释放使表层卤水中的氨15N(≈34.0‰)变得更富集。这种升高的δ15N也记录在从MSC峰的沉积物中分离出来的地卟啉中(≈20‰)，反映了足够的铵供应来维持光养初级生产。我们认为，高效的营养供应、频繁的底层水缺氧和地中海MSC的蒸发物对富有机沉积物的封顶可能是晚中新世大气CO2减少的原因。
The biogeochemistry of hypersaline environments is strongly influenced by changes in biological processes and physicochemical parameters. Although massive evaporation events have occurred repeatedly throughout Earth history, their biogeochemical cycles and global impact remain poorly understood. Here, we provide the first nitrogen isotopic data for nutrients and chloropigments from modern shallow hypersaline environments (solar salterns, Trapani, Italy) and apply the obtained insights to δ15N signatures of the Messinian salinity crisis (MSC) in the late Miocene. Concentrations and δ15N of chlorophylla, bacteriochlorophylla, nitrate, and ammonium in benthic microbial mats indicate that inhibition of nitrification suppresses denitrification and anammox, resulting in efficient ammonium recycling within the mats and high primary productivity. We also suggest that the release of15N-depleted NH3(gas)with increasing salinity enriches ammonium15N in surface brine (≈34.0‰). Such elevated δ15N is also recorded in geoporphyrins isolated from sediments of the MSC peak (≈20‰), reflecting ammonium supply sufficient for sustaining phototrophic primary production. We propose that efficient nutrient supply combined with frequent bottom-water anoxia and capping of organic-rich sediments by evaporites of the Mediterranean MSC could have contributed to atmospheric CO2reduction during the late Miocene.