Salt marshes are important sites of nitrogen cycling and removal that straddle the land/ocean interface, allowing them to intercept human-derived nitrogen before it reaches coastal waters where it causes problems like hypoxia and harmful algal blooms. In 2010, the Deepwater Horizon oil spill released an estimated five million barrels of crude oil into the Gulf of Mexico, significantly contaminating coastal wetlands over approximately 800 km of shoreline. We investigated microbial nitrogen cycling processes in soil from four salt marshes in Terrebonne Bay, Louisiana, USA that were either exposed or not exposed to Deepwater Horizon oil over the course of 1 year (2013–2014), 2.5–3.5 years post-spill. Specifically, we measured nitrification and denitrification potentials, nitrogen cycling functional gene abundances (nirS, bacterial and archaeal amoA), and soil physical and chemical properties. We show that variation in nitrification and denitrification potentials was independent of site oil exposure. Large year-to-year differences in springtime nitrification potentials were inversely related to plant live belowground biomass, indicating that competition for nitrogen is likely an important control on nitrification. There were positive correlations between nitrification potentials and both soil extractable nitrate concentrations and denitrification potentials, supporting the idea that denitrification is coupled with nitrification. We found no evidence that there was a long-term impact of oil exposure on salt marsh soil microbial nitrogen cycling processes and the nitrogen removal ecosystem service they provide. It is important to note, however, that these impacts could have been masked by high background variability in process rates or loss of oil exposed soil to coastal erosion.

中文翻译：

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没有证据表明溢油污染对盐沼土壤氮循环过程产生长期影响

盐沼是跨越陆地/海洋界面的重要氮循环和清除场所，使盐沼能够在人为的氮到达沿海水域之前拦截它们，从而引起缺氧和有害藻华等问题。2010年，“深水地平线”漏油事件估计向墨西哥湾释放了500万桶原油，严重污染了约800公里海岸线上的沿海湿地。我们调查了美国路易斯安那州Terrebonne湾的四个盐沼在土壤中的微生物氮循环过程，这些盐沼在泄漏后2.5年至3.5年的1年内（2013-2014年）暴露于或未暴露于Deepwater Horizo​​n油中。具体来说，我们测量了硝化和反硝化的潜力，氮循环功能基因的丰度（nirS，细菌和古细菌AMOA），土壤理化性质。我们表明，硝化作用和反硝化作用电位的变化与现场油暴露无关。春季硝化潜能的逐年差异与植物体内地下生物量成反比，表明氮竞争可能是硝化的重要控制因素。硝化电位与土壤可提取硝酸盐浓度和反硝化电位之间存在正相关关系，这支持了反硝化与硝化结合的观点。我们没有发现证据表明暴露于石油对盐沼土壤微生物氮循环过程及其提供的脱氮生态系统服务有长期影响。不过，请务必注意