Marine oil spills can impact both coastal and offshore marine environments, but little information is available on how the microbial response to oil and dispersants might differ between these biomes. Here, we describe the compositional and functional response of microbial communities to different concentrations of oil and chemically dispersed oil in coastal and offshore surface waters from the Texas-Louisiana continental shelf. Using a combination of analytical chemistry and 16S rRNA amplicon and metatranscriptomic sequencing, we provide a broad, comparative overview of the ecological response of hydrocarbon-degrading bacteria and their expression of hydrocarbon-degrading genes in marine surface waters over time between two oceanic biomes. We found evidence for the existence of different ecotypes of several commonly described hydrocarbon-degrading bacterial taxa which behaved differentially in coastal and offshore shelf waters despite being exposed to similar concentrations of oil, dispersants, and nutrients. This resulted in the differential expression of catabolic pathways for n-alkanes and polycyclic aromatic hydrocarbons (PAHs)—the two major categories of compounds found in crude oil—with preferential expression of n-alkane degradation genes in coastal waters while offshore microbial communities trended more toward the expression of PAH degradation genes. This was unexpected as it contrasts with the generally held view that n-alkanes, being more labile, are attacked before the more refractory PAHs. Collectively, our results provide new insights into the existence and potential consequences of niche partitioning of hydrocarbon-degrading taxa between neighboring marine environments.

中文翻译：

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沿海和近海架子水之间的生态位分配导致烷烃和多环芳烃分解代谢途径的差异表达。

海洋溢油可能会影响沿海和近海海洋环境，但是关于这些生物群落之间微生物对石油和分散剂的反应如何不同的信息很少。在这里，我们描述了得克萨斯州至路易斯安那州陆架的沿海和近海地表水中微生物群落对不同浓度的石油和化学分散的石油的组成和功能响应。结合分析化学和16S rRNA扩增子及超转录组测序技术，我们提供了两个海洋生物群落之间随着时间推移，烃降解细菌的生态响应及其在海洋表层水域中烃降解基因的表达的广泛而比较的概述。我们发现存在几种通常描述的烃降解细菌类群的不同生态类型的证据，尽管它们暴露于相似浓度的石油，分散剂和养分，但它们在沿海和近海陆架水中的表现却有所不同。这导致了分解代谢途径的差异表达正构烷烃和多环芳烃（PAHs）是原油中的两大类化合物，在沿海水域中优先表达正构烷烃降解基因，而近海微生物群落则更倾向于表达PAH降解基因。这是出乎意料的，因为它与普遍持有的观点相反，后者认为，较不稳定的正构烷烃在难熔的PAHs之前被侵蚀。总的来说，我们的结果为相邻海洋环境之间的可降解碳氢化合物分类单元的生态位划分的存在和潜在后果提供了新的见解。