Novel microbial community composition and carbon biogeochemistry emerge over time following saltwater intrusion in wetlands
Novel microbial community composition and carbon biogeochemistry emerge over time following saltwater intrusion in wetlands
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DOI：
10.1111/gcb.14486
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发表时间：
2019-02-01
影响因子：
11.6
通讯作者：
Franklin, Rima B.
中科院分区：
文献类型：
--
作者：
Dang, Chansotheary;Morrissey, Ember M.;Franklin, Rima B.
海平面上升和降水变化可能导致盐水侵入历史上的淡水湿地，导致微生物代谢的变化，从而改变温室气体排放和土壤碳固存。盐水入侵改变了土壤的物理化学性质，可以立即影响微生物的代谢，但随着时间的推移，随着微生物群落适应变化的环境条件，生物地球化学过程会发生进一步的变化。为了评估海水入侵导致的微生物群落组成和生物地球化学活动的时间变化，将土壤岩心从潮汐淡水沼泽移植到下游的中盐沼泽，并在1年内定期取样。这种实验盐水入侵产生了碳矿化率的直接变化，而群落组成的变化则更为缓慢。盐度对原核生物群落的组成有影响，但对真菌群落的组成影响不大。仅仅在接触盐水一周后，二氧化碳产量就增加了一倍，甲烷产量减少了三个数量级。到1个月时，移植体内的二氧化碳产量与盐水对照相当。随着时间的推移，我们观察到甲烷产量的部分恢复，这与三阶氢营养化产甲烷菌相对丰度的增加密切相关。综上所述，我们的研究结果表明，随着微生物群落和土壤有机碳库之间复杂的相互作用，生态系统对盐水入侵的响应是动态的。我们观察到的微生物群落结构的逐渐变化表明，以前的淡水湿地可能直到最初的盐水入侵后很长时间才经历生态系统功能的平衡。我们的研究结果表明，在这个过渡时期，可能持续数年至数十年，这些生态系统可能通过更大的土壤呼吸和持续的甲烷生成而增加温室气体的产生。
Sea level rise and changes in precipitation can cause saltwater intrusion into historically freshwater wetlands, leading to shifts in microbial metabolism that alter greenhouse gas emissions and soil carbon sequestration. Saltwater intrusion modifies soil physicochemistry and can immediately affect microbial metabolism, but further alterations to biogeochemical processing can occur over time as microbial communities adapt to the changed environmental conditions. To assess temporal changes in microbial community composition and biogeochemical activity due to saltwater intrusion, soil cores were transplanted from a tidal freshwater marsh to a downstream mesohaline marsh and periodically sampled over 1 year. This experimental saltwater intrusion produced immediate changes in carbon mineralization rates, whereas shifts in the community composition developed more gradually. Salinity affected the composition of the prokaryotic community but did not exert a strong influence on the community composition of fungi. After only 1 week of saltwater exposure, carbon dioxide production doubled and methane production decreased by three orders of magnitude. By 1 month, carbon dioxide production in the transplant was comparable to the saltwater controls. Over time, we observed a partial recovery in methane production which strongly correlated with an increase in the relative abundance of three orders of hydrogenotrophic methanogens. Taken together, our results suggest that ecosystem responses to saltwater intrusion are dynamic over time as complex interactions develop between microbial communities and the soil organic carbon pool. The gradual changes in microbial community structure we observed suggest that previously freshwater wetlands may not experience an equilibration of ecosystem function until long after initial saltwater intrusion. Our results suggest that during this transitional period, likely lasting years to decades, these ecosystems may exhibit enhanced greenhouse gas production through greater soil respiration and continued methanogenesis.