Occurrence and activity of anammox bacteria in surface sediments of the southern North Sea@en

We investigated the occurrence and activity of anaerobic ammonia oxidation (anammox) bacteria in sandy and muddy sand sediments of the southern North Sea. The presence of anammox bacteria was established through the detection of specific phosphocholine-monoether ladderane lipids, 16S rRNA gene, and hydrazine synthase (hzsA) genes. Anammox activity was measured in intact sediment cores (in situ rate) and in sediment slurries (potential rate) as the rate of N2 evolution from 15N-labeled substrates and compared to the transcriptional activity of genes of anammox bacteria. The contribution of anammox to N2 production ranged between 0% and 29%. The potential rate of anammox agreed well with the abundance of anammox bacteria 16S rRNA and hzsA gene copies and the transcriptional activity of the anammox bacteria 16S rRNA gene. We found a higher abundance and activity of anammox bacteria in sediments with higher organic carbon content and also higher activity in summer than in winter. The abundance of anammox bacteria and their potential anammox rates were similar to those reported for other marine coastal sediments, suggesting that potentially they are important contributors to the nitrogen cycle in sandy sediments of shallow continental shelf areas.本研究针对北海南部的砂质与砂质泥质沉积物中厌氧氨氧化（anaerobic ammonia oxidation, anammox）细菌的存在与活性展开调查。通过检测特异性磷酸胆碱单醚梯烷脂、16S rRNA基因以及肼合酶（hzsA）基因，确认了厌氧氨氧化细菌的存在。本研究以15N标记底物产生的氮气生成速率为指标，分别测定了原状沉积物岩芯的原位活性与沉积物泥浆的潜在活性，并将其与厌氧氨氧化细菌的基因转录活性进行对比。厌氧氨氧化过程对氮气生成的贡献占比介于0%至29%之间。厌氧氨氧化潜在活性与厌氧氨氧化细菌16S rRNA和hzsA基因拷贝数、以及厌氧氨氧化细菌16S rRNA基因的转录活性均呈现良好的一致性。研究发现，有机碳含量更高的沉积物中厌氧氨氧化细菌的丰度与活性均更高，且夏季的活性显著高于冬季。厌氧氨氧化细菌的丰度及其潜在厌氧氨氧化速率与其他滨海海洋沉积物的已有报道结果相近，表明这类细菌可能是浅海大陆架砂质沉积物氮循环的重要贡献者。