Group of Molecular Microbial Ecology, Institut d'Ecologia Aquàtica, Facultat de Ciències, Universitat de Girona, Edifici Aulari Comú -LEAR, C/ Maria Aurèlia Capmany, 40, 17003, Girona, Catalonia, Spain.
GoodGut, Centre d'Empreses Giroemprèn, Parc Científic i Tecnològic UdG, Carrer Pic de Peguera, 11, 17003, Girona, Catalonia, Spain.
Microb Ecol. 2020 Apr;79(3):588-603. doi: 10.1007/s00248-019-01425-4. Epub 2019 Sep 5.
In constructed wetlands (CW), denitrification usually accounts for > 60% of nitrogen removal and is supposedly affected by wetland management practices, such as dredging (and plant removal). These practices cause an impact in sediment properties and microbial communities living therein. We have quantified the effects of a sediment dredging event on dissimilatory nitrite reduction by analysing the structure and activities of the microbial community before and after the event. Potential rates for nitrate reduction to ammonia and denitrification were in accordance with changes in the physicochemical conditions. Denitrification was the predominant pathway for nitrite removal (> 60%) and eventually led to the complete removal of nitrate. On the contrary, dissimilatory nitrite reduction to ammonia (DNRA) increased from 5 to 18% after the dredging event. Both actual activities and abundances of 16S rRNA, nirK and nirS significantly decreased after sediment dredging. However, genetic potential for denitrification (qnirS + qnirK/q16S rRNA) remained unchanged. Analyses of the 16S rRNA gene sequences revealed the importance of vegetation in shaping microbial community structures, selecting specific phylotypes potentially contributing to the nitrogen cycle. Overall, we confirmed that sediment dredging and vegetation removal exerted a measurable effect on the microbial community, but not on potential nitrite + nitrate removal rates. According to redundancy analysis, nitrate concentration and pH were the main variables affecting sediment microbial communities in the Empuriabrava CWs. Our results highlight a high recovery of the functionality of an ecosystem service after a severe intervention and point to metabolic redundancy of denitrifiers. We are confident these results will be taken into account in future management strategies in CWs.
在人工湿地 (CW) 中，反硝化通常占氮去除的 >60%，并且据称受湿地管理实践的影响，例如疏浚（和植物去除）。这些实践会对沉积物特性和其中的微生物群落产生影响。我们通过分析疏浚事件前后微生物群落的结构和活性，量化了沉积物疏浚事件对异化亚硝酸盐还原的影响。硝酸盐还原为氨和反硝化的潜在速率与理化条件的变化一致。反硝化是去除亚硝酸盐的主要途径（>60%），最终导致硝酸盐的完全去除。相反，异化亚硝酸盐还原为氨（DNRA）在疏浚事件后从 5%增加到 18%。实际活性和 16S rRNA、nirK 和 nirS 的丰度在沉积物疏浚后均显著下降。然而，反硝化的遗传潜力（qnirS + nirK/q16S rRNA）保持不变。16S rRNA 基因序列分析表明，植被在塑造微生物群落结构方面起着重要作用，选择了可能有助于氮循环的特定生物型。总体而言，我们证实沉积物疏浚和植被去除对微生物群落产生了可衡量的影响，但对潜在的亚硝酸盐+硝酸盐去除率没有影响。根据冗余分析，硝酸盐浓度和 pH 是影响 Empuriabrava CWs 沉积物微生物群落的主要变量。我们的结果强调了在严重干预后生态系统服务功能的高度恢复，并指出了反硝化菌的代谢冗余。我们相信这些结果将在未来的 CW 管理策略中得到考虑。
