1. Tube‐dwelling chironomid larvae are among the few taxa that can withstand and thrive in the organic‐rich sediments typical of eutrophic freshwater ecosystems. They can have multiple effects on microbial nitrogen (N) cycling in burrow environments, but such effects cease when chironomid larvae undergo metamorphosis into flying adults and leave the sediment.
2. Here we investigated the ecological role of Chironomus plumosus by exploring the effect of its different life stages (as larva and adult midge) on microbial N transformations in a shallow freshwater lagoon by means of combined biogeochemical and molecular approaches. Results suggest that sediment bioturbation by chironomid larvae produce contrasting effects on nitrate ()‐reduction processes.
3. Denitrification was the dominant pathway of reduction (>90%), primarily fuelled by from bottom water. In addition to pumping ‐rich bottom water within the burrows, chironomid larvae host microbiota capable of reduction. However, the contribution of larval microbiota is lower than that of microbes inhabiting the burrow walls. Interestingly, dinitrogen fixation co‐occurred with reduction processes, indicating versatility of the larvae's microbial community.
4. Assuming all larvae (averaging 1,800 ind./m²) leave the sediment following metamorphosis into flying adults, we estimated a displacement of 47,787 µmol of organic N/m² from the sediment to the atmosphere during adult emergence. This amount of particulate organic N is similar to the entire N removal stimulated by larvae denitrification over a period of 20 days.
5. Finally, the detection of N‐cycling marker genes in flying adults suggests that these insects retain N‐cycling microbes during metamorphosis and migration to the aerial and terrestrial ecosystems. This study provides evidence that chironomids have a multifaceted role in shaping the N cycle of aquatic ecosystems.

中文翻译：

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生物扰动器，整体环和载体：Chironomus plumosus在塑造N循环中的多方面作用

1. 管栖类幼虫是少数能够在富营养化淡水生态系统典型的富含有机物的沉积物中生存并繁衍的类群。它们可对洞穴环境中的微生物氮循环产生多种影响，但当拟虫幼虫变态成飞行成年并离开沉积物时，这种作用就停止了。
2. 在这里，我们通过结合生物地球化学和分子生物学方法，探索了Chironomus plumosus的不同生命阶段（如幼虫和成年蚊）对浅水泻湖中微生物N转化的影响，从而研究了其生态作用。结果表明，尺虫幼虫对沉积物的生物扰动对硝酸盐还原过程产生了相反的影响。
3. 反硝化是主要的减少途径（> 90％），主要由底水推动。除将丰富的底水泵入洞穴外，尺虫幼虫还具有能够还原的微生物群。然而，幼虫微生物群的贡献低于居住在洞穴壁中的微生物的贡献。有趣的是，还原过程同时发生了固氮作用，表明幼虫的微生物群落具有多功能性。
4. 假设所有幼虫（平均1,800 ind./m ²）在变态后都离开沉积物进入飞行的成虫，我们估计成年出现时从沉积物中到大气中的有机N / m ²的有机氮排泄量为47,787 µmol 。颗粒状有机氮的量类似于幼体反硝化在20天内刺激的全部N去除。
5. 最后，在飞行中的成虫中检测N-循环标记基因表明，这些昆虫在变态以及向空中和陆地生态系统迁移过程中保留了N-循环微生物。这项研究提供了证据，证明了拟生物体在塑造水生生态系统的N循环中具有多方面的作用。