359
294, a site where 3D seismic reflectivity data suggested the presence of hard grounds
(White et al. 2012b). At this site, located 13 km from the well at a depth of 1370 m,
the majority of corals were, at least partially, covered in a brown flocculent material
(floc) and displayed signs of stress such as tissue loss and excess mucus production.
Analyses of the floc revealed that it contained traces of oil from the Macondo well
as well as dioctyl sodium sulfosuccinate, a component of the dispersant deployed
during the spill (White et al. 2012b, 2014). The composition of the floc, coupled
with the location, timing of occurrence, and the fact that no visual damage has been
observed on any other coral communities in the last decade, strongly links the damages observed at MC 294 to the DWH oil spill (White et al. 2012a).
The coral community at MC 294 was dominated by the octocoral species
Paramuricea biscaya (Grasshoff 1977), although a few other species such as
Paragorgia regalis (Nutting 1913) and Swiftia spp. were present and showed signs
of impact. Toxicity experiments performed on a closely related species
(Paramuricea sp. B3) indicated that if oil alone had little effect on coral’s health,
mixtures of oil and dispersant, as found in the floc, were particularly toxic to corals
(DeLeo et al. 2015).
P. biscaya colonies were associated with hormathiid anemones and ophiuroids of
the species Asteroschema clavigerum (Verrill 1894) (Hsing et al. 2013; White et al.
2012b). Ophiuroids were observed on the majority of coral colonies, and several
individuals displayed an abnormal white color (A. clavigerum is generally tan to red
in color). Additionally, several ophiuroids had loosely coiled or splayed out arms, an
unusual behavior for this species (White et al. 2012b). These observations suggested an impact of the spill on ophiuroids associated with corals at MC 294.
22.2.3 Hard-Bottoms After DWH (2011–2014)
To determine whether other coral communities were impacted by the spill, surveys
using towed cameras and autonomous underwater vehicles (AUVs) were conducted
in 2011 in the vicinity of the Macondo well. These surveys led to the discovery of
five previously unknown coral communities, and further exploration of these sites
using remotely operated vehicles (ROVs) resulted in the identification of two additional impacted coral communities (Fisher et al. 2014a, b). These communities were
located in lease blocks MC 297 and MC 344, 6 and 22 km from the Macondo well
at 1560 and 1850 m depths, respectively (Fisher et al. 2014b). Both coral communities were dominated by Paramuricea biscaya, the same coral species present at MC
294. At these two sites, corals were no longer covered in floc but displayed the
characteristic patchy impact and hydroid colonization also observed at MC 294 at
this point in time (Fisher et al. 2014b).
Paramuricea biscaya has a planar morphology and is thus well suited for image
analysis as all branches can be seen on the same image. Therefore, an image-based
monitoring program was initiated in 2010 at MC 294 and 2011 at MC 297 and MC
344 in order to characterize the recovery of corals impacted by the spill. Over 300
22 Deep-Sea Benthic Faunal Impacts and Community Evolution Before, During…
294, a site where 3D seismic reflectivity data suggested the presence of hard grounds
(White et al. 2012b). At this site, located 13 km from the well at a depth of 1370 m,
the majority of corals were, at least partially, covered in a brown flocculent material
(floc) and displayed signs of stress such as tissue loss and excess mucus production.
Analyses of the floc revealed that it contained traces of oil from the Macondo well
as well as dioctyl sodium sulfosuccinate, a component of the dispersant deployed
during the spill (White et al. 2012b, 2014). The composition of the floc, coupled
with the location, timing of occurrence, and the fact that no visual damage has been
observed on any other coral communities in the last decade, strongly links the damages observed at MC 294 to the DWH oil spill (White et al. 2012a).
The coral community at MC 294 was dominated by the octocoral species
Paramuricea biscaya (Grasshoff 1977), although a few other species such as
Paragorgia regalis (Nutting 1913) and Swiftia spp. were present and showed signs
of impact. Toxicity experiments performed on a closely related species
(Paramuricea sp. B3) indicated that if oil alone had little effect on coral’s health,
mixtures of oil and dispersant, as found in the floc, were particularly toxic to corals
(DeLeo et al. 2015).
P. biscaya colonies were associated with hormathiid anemones and ophiuroids of
the species Asteroschema clavigerum (Verrill 1894) (Hsing et al. 2013; White et al.
2012b). Ophiuroids were observed on the majority of coral colonies, and several
individuals displayed an abnormal white color (A. clavigerum is generally tan to red
in color). Additionally, several ophiuroids had loosely coiled or splayed out arms, an
unusual behavior for this species (White et al. 2012b). These observations suggested an impact of the spill on ophiuroids associated with corals at MC 294.
22.2.3 Hard-Bottoms After DWH (2011–2014)
To determine whether other coral communities were impacted by the spill, surveys
using towed cameras and autonomous underwater vehicles (AUVs) were conducted
in 2011 in the vicinity of the Macondo well. These surveys led to the discovery of
five previously unknown coral communities, and further exploration of these sites
using remotely operated vehicles (ROVs) resulted in the identification of two additional impacted coral communities (Fisher et al. 2014a, b). These communities were
located in lease blocks MC 297 and MC 344, 6 and 22 km from the Macondo well
at 1560 and 1850 m depths, respectively (Fisher et al. 2014b). Both coral communities were dominated by Paramuricea biscaya, the same coral species present at MC
294. At these two sites, corals were no longer covered in floc but displayed the
characteristic patchy impact and hydroid colonization also observed at MC 294 at
this point in time (Fisher et al. 2014b).
Paramuricea biscaya has a planar morphology and is thus well suited for image
analysis as all branches can be seen on the same image. Therefore, an image-based
monitoring program was initiated in 2010 at MC 294 and 2011 at MC 297 and MC
344 in order to characterize the recovery of corals impacted by the spill. Over 300
22 Deep-Sea Benthic Faunal Impacts and Community Evolution Before, During…