Data_Sheet_1_Temporal variability of microbial response to crude oil exposure in the northern Gulf of Mexico.PDF

Oil spills are common occurrences in the United States and can result in extensive ecological damage. The 2010 Deepwater Horizon oil spill in the Gulf of Mexico was the largest accidental spill recorded. Many studies were performed in deep water habitats to understand the microbial response to the released crude oil. However, much less is known about how planktonic coastal communities respond to oil spills and whether that response might vary over the course of the year. Understanding this temporal variability would lend additional insight into how coastal Florida habitats may have responded to the Deepwater Horizon oil spill. To assess this, the temporal response of planktonic coastal microbial communities to acute crude oil exposure was examined from September 2015 to September 2016 using seawater samples collected from Pensacola Beach, Florida, at 2-week intervals. A standard oil exposure protocol was performed using water accommodated fractions made from MC252 surrogate oil under photo-oxidizing conditions. Dose response curves for bacterial production and primary production were constructed from 3H-leucine incorporation and 14C-bicarbonate fixation, respectively. To assess drivers of temporal patterns in inhibition, a suite of biological and environmental parameters was measured including bacterial counts, chlorophyll a, temperature, salinity, and nutrients. Additionally, 16S rRNA sequencing was performed on unamended seawater to determine if temporal variation in the in situ bacterial community contributed to differences in inhibition. We observed that there is temporal variation in the inhibition of primary and bacterial production due to acute crude oil exposure. We also identified significant relationships of inhibition with environmental and biological parameters that quantitatively demonstrated that exposure to water-soluble crude oil constituents was most detrimental to planktonic microbial communities when temperature was high, when there were low inputs of total Kjeldahl nitrogen, and when there was low bacterial diversity or low phytoplankton biomass.

原油泄漏在美国是常见事件，且可造成大范围生态破坏。2010年墨西哥湾深水地平线（Deepwater Horizon）漏油事件是有记录以来规模最大的意外原油泄漏事故。此前已有多项研究聚焦深水生境，旨在探明其微生物对泄漏原油的响应机制。然而，目前对于沿岸浮游群落如何响应原油泄漏，以及该响应是否随年度周期发生变化，仍缺乏充分认知。厘清这类时间变异性，将有助于进一步理解佛罗里达沿岸生境对深水地平线漏油事件的响应模式。
为探究这一科学问题，本研究于2015年9月至2016年9月期间，以每两周一次的频次采集佛罗里达州彭萨科拉海滩的海水样本，以此分析沿岸浮游微生物群落对急性原油暴露的时间响应特征。
实验采用标准原油暴露方案，在光氧化条件下利用MC252替代原油制备水包油馏分（water accommodated fractions, WAF）开展处理。研究分别通过3H-亮氨酸掺入法与14C-碳酸氢盐固定法，构建了细菌生产力与初级生产力的剂量-反应曲线。
为解析抑制效应时间模式的驱动因子，本研究测定了一系列生物学与环境参数，包括细菌计数、叶绿素a、温度、盐度及营养盐含量。此外，本研究对未添加外源处理的原位海水样本开展16S rRNA测序，以明确原位细菌群落的时间变异是否会导致抑制效应的差异。
研究结果显示，急性原油暴露对初级生产力与细菌生产力的抑制效应存在显著时间变异性。本研究还发现抑制效应与多项环境及生物学参数存在显著关联，定量结果表明：当温度较高、总凯氏氮（total Kjeldahl nitrogen, TKN）输入量较低，以及细菌多样性或浮游植物生物量偏低时，水溶性原油组分暴露对浮游微生物群落的损害最为严重。