Dept. of Marine Science, Texas A & M University at Galveston, Galveston, TX 77553, USA.
Dept. of Marine Science, Texas A & M University at Galveston, Galveston, TX 77553, USA.
Sci Total Environ. 2019 Nov 25;693:133626. doi: 10.1016/j.scitotenv.2019.133626. Epub 2019 Jul 26.
Large amounts of oil containing mucous-like marine snow formed in surface waters adjacent to the Deepwater Horizon spill that was implicated in oil delivery to the seafloor. However, whether chemical dispersants that were used increased or decreased the oil incorporation and sedimentation efficiency, and how exopolymeric substances (EPS) are involved in this process remains unresolved. To investigate the microbial responses to oil and dispersants in different oceanic settings, indicated by EPS production, petro- and non-petro carbon sedimentation, four mesocosm (M) experiments were conducted: 1) nearshore seawater with a natural microbial consortia (M2); 2) offshore seawater with f/20 nutrients (M3); 3) coastal seawater with f/20 nutrients (M4); 4) nearshore seawater with a natural microbial consortia for a longer duration (M5). Four treatments were conducted in M2, M3 and M4 whereas only three in M5: 1) a water accommodated fraction of oil (WAF), 2) a chemically-enhanced WAF prepared with Corexit (CEWAF, not in M5), 3) a 10-fold diluted CEWAF (DCEWAF); and 4) controls. Overall, oil and dispersants input, nutrient and microbial biomass addition enhanced EPS production. Dispersant addition tended to induce the production of EPS with higher protein/carbohydrate (P/C) ratios, irrespective of oceanic regions. EPS produced in M4 was generally more hydrophobic than that produced in M3. The P/C ratio of EPS in both the aggregate and the colloidal fraction was a key factor that regulated oil contribution to sinking aggregates, based on the close correlation with %petro-carbon in these fractions. In the short term (4-5 days), both the petro and non-petro carbon sedimentation efficiencies showed decreasing trends when oil/dispersants were present. In comparison, in the longer-term (16 days), petro-carbon sedimentation efficiency was less influenced by dispersants, possibly due to biological and physicochemical changes of the components of the oil-EPS-mineral phase system, which cooperatively controlled the sinking velocities of the aggregates.
大量含有黏液状海洋雪的石油在与深水地平线溢油事件相关的海域形成，该溢油事件被认为是石油输送到海底的原因。然而，使用的化学分散剂是否增加或减少了石油的掺入和沉降效率，以及外多聚物物质（EPS）如何参与这一过程仍未得到解决。为了研究海洋环境中微生物对石油和分散剂的反应，通过 EPS 产生、石油和非石油碳的沉降来指示，进行了四个中观（M）实验：1）近岸海水与天然微生物群落（M2）；2）近海海水与 f/20 营养物（M3）；3）沿海海水与 f/20 营养物（M4）；4）近岸海水与天然微生物群落的更长时间（M5）。在 M2、M3 和 M4 中进行了四种处理，而在 M5 中仅进行了三种处理：1）水可容纳油分数（WAF），2）用科里克斯（Corexit）制备的化学增强 WAF（CEWAF，M5 中没有），3）10 倍稀释的 CEWAF（DCEWAF）；和 4）对照。总体而言，石油和分散剂的输入、营养物和微生物生物量的添加增强了 EPS 的产生。分散剂的添加往往会诱导 EPS 产生更高的蛋白质/碳水化合物（P/C）比，而与海洋区域无关。M4 中产生的 EPS 通常比 M3 中产生的更疏水。在基于与这些部分的 %石油碳的密切相关性的情况下，EPS 在聚集物和胶体部分中的 P/C 比是调节石油对下沉聚集物的贡献的关键因素。在短期（4-5 天）内，当存在石油/分散剂时，石油和非石油碳的沉降效率都呈现出下降的趋势。相比之下，在较长时间（16 天）内，石油碳的沉降效率受分散剂的影响较小，这可能是由于石油-EPS-矿物相系统的成分发生了生物和物理化学变化，这些变化共同控制了聚集物的下沉速度。
