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.

中文翻译：

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Empuriabrava FWS-CW中的泥沙疏and和去除植物后，亚硝酸盐还原剂的潜在活性和微生物群落结构的变化。

在人工湿地（CW）中，反硝化通常占氮去除量的60％以上，据推测会受到诸如疏land（和植物去除）之类的湿地管理方法的影响。这些做法会对沉积物特性和其中的微生物群落产生影响。通过分析事件发生前后微生物群落的结构和活性，我们量化了泥沙疏event事件对异化亚硝酸盐还原的影响。硝酸盐还原成氨和反硝化的潜在速率取决于理化条件的变化。反硝化是亚硝酸盐去除的主要途径（> 60％），最终导致硝酸盐的完全去除。反之，疏event事件发生后，异化亚硝酸盐还原为氨（DNRA）的比例从5％增加到18％。沉积物疏after后，实际活动和16S rRNA，nirK和nirS的丰度均显着降低。但是，反硝化的遗传潜力（qnirS + qnirK / q16S rRNA）保持不变。对16S rRNA基因序列的分析揭示了植被在塑造微生物群落结构，选择可能有助于氮循环的特定系统型方面的重要性。总体而言，我们确认了泥沙疏and和植被去除对微生物群落产生了可测量的影响，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连续水处理厂沉积物微生物群落的主要变量。我们的结果表明，经过严格的干预后，生态系统服务的功能将得到高度恢复，并指出反硝化器的代谢冗余。我们相信，这些结果将在CW的未来管理策略中得到考虑。