Energy, Mining and Environment Research Center, National Research Council Canada, Montreal, Quebec, Canada
Energy, Mining and Environment Research Center, National Research Council Canada, Montreal, Quebec, Canada.
Appl Environ Microbiol. 2019 May 2;85(10). doi: 10.1128/AEM.00086-19. Print 2019 May 15.
Western Canada produces large amounts of bitumen, a heavy, highly weathered crude oil. Douglas Channel and Hecate Strait on the coast of British Columbia are two water bodies that may be impacted by a proposed pipeline and marine shipping route for diluted bitumen (dilbit). This study investigated the potential of microbial communities from these waters to mitigate the impacts of a potential dilbit spill. Microcosm experiments were set up with water samples representing different seasons, years, sampling stations, and dilbit blends. While the alkane fraction of the tested dilbit blends was almost completely degraded after 28 days, the majority of the polycyclic aromatic hydrocarbons (PAHs) remained. The addition of the dispersant Corexit 9500A most often had either no effect or an enhancing effect on dilbit degradation. Dilbit-degrading microbial communities were highly variable between seasons, years, and stations, with dilbit type having little impact on community trajectories. Potential oil-degrading genera showed a clear succession pattern and were for the most part recruited from the "rare biosphere." At the community level, dispersant appeared to stimulate an accelerated enrichment of genera typically associated with hydrocarbon degradation, even in dilbit-free controls. This suggests that dispersant-induced growth of hydrocarbon degraders (and not only increased bioavailability of oil-associated hydrocarbons) contributes to the degradation-enhancing effect previously reported for Corexit 9500A. Western Canada hosts large petroleum deposits, which ultimately enter the market in the form of dilbit. Tanker-based shipping represents the primary means to transport dilbit to international markets. With anticipated increases in production to meet global energy needs, the risk of a dilbit spill is expected to increase. This study investigated the potential of microbial communities naturally present in the waters of a potential dilbit shipping lane to mitigate the effects of a spill. Here we show that microbial degradation of dilbit was mostly limited to -alkanes, while the overall concentration of polycyclic aromatic hydrocarbons, which represent the most toxic fraction of dilbit, decreased only slightly within the time frame of our experiments. We further investigated the effect of the oil dispersant Corexit 9500A on microbial dilbit degradation. Our results highlight the fact that dispersant-associated growth stimulation, and not only increased bioavailability of hydrocarbons and inhibition of specific genera, contributes to the overall effect of dispersant addition.
加拿大西部生产大量的沥青，这是一种重质、高度风化的原油。不列颠哥伦比亚省的道格拉斯海峡和赫卡特海峡是两个可能受到拟议的管道和稀释沥青（稀释沥青）海运航线影响的水体。本研究调查了这些水域中的微生物群落减轻潜在稀释沥青泄漏影响的潜力。使用代表不同季节、年份、采样站和稀释沥青混合物的水样进行微宇宙实验。虽然测试的稀释沥青混合物中的烷烃部分在 28 天后几乎完全降解，但大多数多环芳烃（PAHs）仍然存在。添加分散剂 Corexit 9500A 通常要么没有效果，要么对稀释沥青的降解有促进作用。稀释沥青降解微生物群落在季节、年份和站位之间差异很大，稀释沥青类型对群落轨迹几乎没有影响。潜在的石油降解属表现出明显的演替模式，并且大部分是从“稀有生物圈”中招募的。在群落水平上，分散剂似乎刺激了通常与碳氢化合物降解相关的属的加速富集，即使在没有稀释沥青的对照中也是如此。这表明，分散剂诱导的烃类降解菌的生长（而不仅仅是增加了与油相关的烃类的生物利用度）有助于解释先前报道的 Corexit 9500A 的降解增强效应。加拿大西部拥有大量的石油储量，最终以稀释沥青的形式进入市场。油轮运输是将稀释沥青运往国际市场的主要方式。随着满足全球能源需求的产量预期增加，稀释沥青泄漏的风险预计将会增加。本研究调查了潜在稀释沥青运输航道水域中自然存在的微生物群落减轻泄漏影响的潜力。在这里，我们表明，微生物对稀释沥青的降解主要限于 -烷烃，而在我们实验的时间范围内，代表稀释沥青最有毒部分的多环芳烃的总体浓度仅略有下降。我们进一步研究了石油分散剂 Corexit 9500A 对微生物稀释沥青降解的影响。我们的结果强调了这样一个事实，即分散剂相关的生长刺激，而不仅仅是增加碳氢化合物的生物利用度和抑制特定属，有助于分散剂添加的整体效果。
