Chemical analysis of sediment and fish species near the Hercules 265 blowout, Gulf of Mexico, 2013

On July 23, 2013 a marine gas rig (Hercules 265) ignited in the northern Gulf of Mexico. The rig burned out of control for several days before being extinguished. We conducted a rapid-response sampling campaign near Hercules 265 after the fire to ascertain if sediments and fishes were polluted above earlier baseline levels. Sediment cores were collected to the SE of the rig at a distance of ~0.2 km, 8 km and 18 km using a multicorer, and demersal fishes were collected from ~0.2 to 8 km SE of the rig using a longline (508 hooks). Recently deposited sediments document that only high molecular weight (HMW) polycyclic aromatic hydrocarbon (PAH) concentrations decreased with increasing distance from the rig suggesting higher pyrogenic inputs associated with the blowout. A similar trend was observed in the foraminifera Haynesina germanica, an indicator species of pollution. In red snapper bile, only HMW PAH metabolites increased in 2013 nearly double those from 2012. Both surface sediments and fish bile analyses suggest that, in the aftermath of the blowout, increased concentration of pyrogenically-derived hydrocarbons were transported and deposited in the environment. This study further emphasizes the need for an ocean observing system and coordinated rapid-response efforts from an array of scientific disciplines to effectively assess environmental impacts resulting from accidental releases of contaminants.

2013年7月23日，墨西哥湾北部的海上天然气钻井平台（Hercules 265）发生起火事故，该平台失控燃烧多日后才被扑灭。事故发生后，我们针对Hercules 265开展了快速响应采样行动，以探明沉积物与鱼类的污染水平是否高于此前的本底值。研究人员使用多管采样器（multicorer），在该钻井平台东南方向约0.2 km、8 km及18 km处采集了沉积物岩芯（sediment cores）；同时使用延绳钓（longline，配备508枚钓钩）在该平台东南方向0.2~8 km范围内采集了底栖鱼类（demersal fishes）。近期沉积的沉积物数据显示，仅高分子量（high molecular weight, HMW）多环芳烃（polycyclic aromatic hydrocarbon, PAH）的浓度随距离钻井平台的距离增加而降低，表明此次井喷事件伴随了更高的热解成因输入物。在有孔虫（foraminifera）德国海恩斯虫（Haynesina germanica）——一种污染指示物种——体内也观测到了类似的浓度变化趋势。对红笛鲷（red snapper）胆汁的检测结果显示，2013年仅HMW PAH代谢物浓度出现上升，较2012年水平提升近一倍。表层沉积物与鱼类胆汁的分析结果均表明，井喷事件后，热解成因烃类物质的浓度出现上升，并被搬运、沉积至周边环境中。本研究进一步强调，需建立海洋观测系统（ocean observing system），并协调多学科科研团队开展快速响应工作，以有效评估污染物意外泄漏造成的环境影响。