Data from: Evidence of lasting impact of the Deepwater Horizon oil spill on a deep Gulf of Mexico coral community

A coral community 11 km southwest of the site of the Deepwater Horizon blowout at 1,370 m water depth was discovered 3.5 months after the well was capped on 3 November 2010. Gorgonian corals at the site were partially covered by a brown flocculent material (floc) that contained hydrocarbons fingerprinted to the oil spill. Here we quantify the visible changes to the corals at this site during five visits over 17 months by digitizing images of individual branches of each colony and categorizing their condition. Most of the floc visible in November 2010 was absent from the corals by the third visit in March 2011, and there was a decrease in the median proportions of the colonies showing obvious signs of impact after the first visit. During our second visit in 2010, about six weeks after the first, we documented the onset of hydroid colonization (a sign of coral deterioration) on impacted coral branches that increased over the remainder of the study. Hydroid colonization of impacted portions of coral colonies by the last visit in March 2012 correlated positively with the proportion of the colony covered by floc during the first two visits in late 2010. Similarly, apparent recovery of impacted portions of the coral by March 2012 correlated negatively with the proportion of the coral covered with floc in late 2010. A notable feature of the impact was its patchy nature, both within and among colonies, suggesting that the impacting agent was not homogeneously dispersed during initial contact with the corals. While the median level of obvious visible impact decreased over time, the onset of hydroid colonization and the probability of impacts that were not visually obvious suggest that future visits may reveal additional deterioration in the condition of these normally long-lived corals.

2010年11月3日油井封井后3.5个月，科研人员在水深1370米、深水地平线（Deepwater Horizon）井喷点西南11公里的海域，发现了一处珊瑚群落。该区域的柳珊瑚（Gorgonian corals）部分被棕褐色絮凝物（floc）覆盖，该絮凝物中含有的烃类物质指纹特征与此次漏油事件完全匹配。本研究通过对每个珊瑚群落的单根分枝图像进行数字化处理，并对其健康状态进行分类评级，量化了17个月内5次科考造访期间该区域珊瑚的可见变化。2010年11月可见的大部分絮凝物，在2011年3月第三次科考时已从珊瑚表面消失；首次科考后，出现明显受损迹象的珊瑚群落比例中位数有所下降。2010年第二次科考（距首次科考约6周）期间，我们记录到受损珊瑚分枝上出现水螅虫（hydroid）定殖现象——这是珊瑚退化的标志性特征，且该现象在后续研究期间持续增多。截至2012年3月最后一次科考时，珊瑚群落受损区域的水螅虫定殖程度，与2010年末前两次科考中该群落被絮凝物覆盖的比例呈正相关。与之类似，截至2012年3月，珊瑚受损区域的表观恢复程度与2010年末珊瑚被絮凝物覆盖的比例呈负相关。此次珊瑚受损的一个显著特征是其斑块状分布特性，既存在于单个珊瑚群落内部，也存在于不同群落之间，这表明损伤因子在初次接触珊瑚时并未均匀扩散。尽管肉眼可见的明显受损程度中位数随时间推移有所下降，但水螅虫定殖的出现以及存在肉眼难以察觉的受损的可能性，意味着后续科考可能会发现这些通常寿命较长的珊瑚出现更多退化情况。