Strong Seasonality in Arctic Estuarine Microbial Food Webs
Strong Seasonality in Arctic Estuarine Microbial Food Webs
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DOI：
10.3389/fmicb.2019.02628
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发表时间：
2019-11-29
影响因子：
5.2
通讯作者：
Crump, Byron C.
中科院分区：
文献类型：
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作者：
Kellogg, Colleen T. E.;McClelland, James W.;Crump, Byron C.
由于海冰范围和淡水输入的季节性变化，北冰洋沿岸的微生物群落的有机物和无机营养物经历了极大的变化。泻湖毗邻波弗特海海岸的一半以上，为洄游鱼类和海鸟提供了重要的栖息地；然而，人们对支持这些较高营养水平的浮游食物网知之甚少。为了研究细菌和原生生物浮游群落的季节变化，我们从 2011 年至 2013 年冰盖（4 月）、冰崩（6 月）和开放水域（8 月）期间从阿拉斯加东部波弗特海海岸的浅泻湖收集的样本中生成了 16S 和 18S rRNA 基因的扩增子序列。原生生物群落从异养类群转变为光合类群（主要是 硅藻）在冬春过渡期间，然后回到异养主导的夏季群落，其中包括甲藻和混合营养型超微型浮游植物，如小单胞菌和深球藻。冬季，当外源碳输入较低时，属于 Syndiniales 的浮游寄生虫在冰下大量存在。细菌群落在冬春过渡期间从沿海海洋类群（Oceanospirillaceae、Altereromonadales）转移到河口类群（Polaromonas、Bacteroidetes），然后在夏季转移到寡营养海洋类群（SAR86、SAR92）。冰下化学自养类群丰富，包括铁氧化Zetaproteobacteria。这些结果表明，冬季北极细菌群落利用了近岸冰层下方形成的独特生物地球化学梯度，在系统碳输入较低时可能利用化学自养代谢。为每个季节构建的共现网络表明，冰下网络以寄生原生生物和其他微生物类群之间的关系为主，而春季网络是迄今为止最大的，以细菌-细菌共现为主。夏季网络是最小的，连接也最少，这表明食物网更多地以碎屑为基础，较少依赖微生物类群之间的相互作用。真核生物和细菌群落组成与颗粒有机碳和氮的稳定同位素浓度趋势以及其他物理化学变量（例如溶解氧、盐度和温度）显着相关。这表明海冰覆盖和陆地碳补贴对于影响波弗特海沿岸微生物群落季节性趋势的重要性。
Microbial communities in the coastal Arctic Ocean experience extreme variability in organic matter and inorganic nutrients driven by seasonal shifts in sea ice extent and freshwater inputs. Lagoons border more than half of the Beaufort Sea coast and provide important habitats for migratory fish and seabirds; yet, little is known about the planktonic food webs supporting these higher trophic levels. To investigate seasonal changes in bacterial and protistan planktonic communities, amplicon sequences of 16S and 18S rRNA genes were generated from samples collected during periods of ice-cover (April), ice break-up (June), and open water (August) from shallow lagoons along the eastern Alaska Beaufort Sea coast from 2011 through 2013. Protist communities shifted from heterotrophic to photosynthetic taxa (mainly diatoms) during the winter-spring transition, and then back to a heterotroph-dominated summer community that included dinoflagellates and mixotrophic picophytoplankton such as Micromonas and Bathycoccus. Planktonic parasites belonging to Syndiniales were abundant under ice in winter at a time when allochthonous carbon inputs were low. Bacterial communities shifted from coastal marine taxa (Oceanospirillaceae, Alteromonadales) to estuarine taxa (Polaromonas, Bacteroidetes) during the winter-spring transition, and then to oligotrophic marine taxa (SAR86, SAR92) in summer. Chemolithoautotrophic taxa were abundant under ice, including iron-oxidizing Zetaproteobacteria. These results suggest that wintertime Arctic bacterial communities capitalize on the unique biogeochemical gradients that develop below ice near shore, potentially using chemoautotrophic metabolisms at a time when carbon inputs to the system are low. Co-occurrence networks constructed for each season showed that under-ice networks were dominated by relationships between parasitic protists and other microbial taxa, while spring networks were by far the largest and dominated by bacteria-bacteria co-occurrences. Summer networks were the smallest and least connected, suggesting a more detritus-based food web less reliant on interactions among microbial taxa. Eukaryotic and bacterial community compositions were significantly related to trends in concentrations of stable isotopes of particulate organic carbon and nitrogen, among other physiochemical variables such as dissolved oxygen, salinity, and temperature. This suggests the importance of sea ice cover and terrestrial carbon subsidies in contributing to seasonal trends in microbial communities in the coastal Beaufort Sea.