Laminarin is a major molecule in the marine carbon cycle
Laminarin is a major molecule in the marine carbon cycle
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DOI：
10.1073/pnas.1917001117
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发表时间：
2020-03-24
影响因子：
11.1
通讯作者：
Hehemann, Jan-Hendrik
中科院分区：
文献类型：
--
作者：
Becker, Stefan;Tebben, Jan;Hehemann, Jan-Hendrik
海洋微藻与陆地植物一样，将二氧化碳封存为碳水化合物。聚合碳水化合物（即，聚糖）为异养生物提供碳，并构成全球海洋中的碳汇。不同藻类聚糖对碳循环和固碳的定量贡献仍然未知，部分原因是量化复杂生物基质中聚糖的分析挑战。在这里，我们使用最近开发的生物催化策略定量了聚糖结构类型，该策略涉及海带多糖酶，其特异性地将藻类聚糖海带多糖切割成易于分析的片段。我们测量海带多糖沿着断面在北极，大西洋和太平洋，并在三个时间序列在北海。这些数据显示，颗粒有机碳库中的海带多糖的中位数为26 +/- 17%。观察到的叶绿素和海带多糖之间的相关性表明，藻类海带多糖的年产量为12 +/- 8千兆吨：也就是说，大约是化石燃料燃烧每年增加的大气二氧化碳的三倍。此外，我们的数据显示，海带多糖占50%的有机碳在下沉的含磷颗粒，从而大大有助于从表面沃茨的碳输出。在阳光照射的海洋中，海带多糖浓度的时空变化是由光的可用性驱动的。总的来说，这些观察结果突出了海带多糖在海洋碳输出和能量流向更高营养级中的突出生态作用和生态地球化学功能。
Marine microalgae sequester as much CO2 into carbohydrates as terrestrial plants. Polymeric carbohydrates (i.e., glycans) provide carbon for heterotrophic organisms and constitute a carbon sink in the global oceans. The quantitative contributions of different algal glycans to cycling and sequestration of carbon remain unknown, partly because of the analytical challenge to quantify glycans in complex biological matrices. Here, we quantified a glycan structural type using a recently developed biocatalytic strategy, which involves laminarinase enzymes that specifically cleave the algal glycan laminarin into readily analyzable fragments. We measured laminarin along transects in the Arctic, Atlantic, and Pacific oceans and during three time series in the North Sea. These data revealed a median of 26 +/- 17% laminarin within the particulate organic carbon pool. The observed correlation between chlorophyll and laminarin suggests an annual production of algal laminarin of 12 +/- 8 gigatons: that is, approximately three times the annual atmospheric carbon dioxide increase by fossil fuel burning. Moreover, our data revealed that laminarin accounted for up to 50% of organic carbon in sinking diatom-containing particles, thus substantially contributing to carbon export from surface waters. Spatially and temporally variable laminarin concentrations in the sunlit ocean are driven by light availability. Collectively, these observations highlight the prominent ecological role and biogeochemical function of laminarin in oceanic carbon export and energy flow to higher trophic levels.