where the corals and communities appeared unchanged.
However, at one site 11 km southwest of the Macondo well, coral colonies presented widespread signs of stress, including varying degrees of tissue loss, sclerite enlargement, excessmucous production, bleached commensal ophiuroids, and covering by brown flocculent material (floc).
On the basis of these criteria the level of impact to individual colonies was ranked from 0 (least impact) to 4 (greatest impact). Of the 43 corals imaged at that site, 46% exhibited evidence of impact onmore than half of the colony,whereas nearly a quarter of all of the
corals showed impact to >90% of the colony. Additionally, 53% of these corals’ ophiuroid associates displayed abnormal color and/or attachment posture.
Analysis of hopanoid petroleumbiomarkers isolated from the floc provides strong evidence that this material contained oil fromtheMacondowell.
The presence of recently damaged and deceased corals beneath the path of a previously documented
plume emanating from the Macondo well provides compelling evidence that the oil impacted deep-water ecosystems.
Our findings underscore the unprecedented nature of the spill in terms of its magnitude,
release at depth, and impact to deep-water ecosystems.