368
The meiofauna and macrofauna community responses were re-examined again
in June 2014, approximately 4 years after the oil stopped flowing (Reucsher et al.
2017). The same 34 stations were sampled as in 2010 and 2011 from the impact
zone and the non-impact zone. Even though chemical contaminant concentrations
decreased slightly, they were still significantly different between the two zones.
PAH concentrations averaged 218 ppb in the impact zone compared to 14 ppb in the
non-impact zone. TPH concentrations averaged 1166 ppm in the impact zone compared to 102 ppm in the non-impact zone. While there was no difference between
zones for meiofauna and macrofauna abundance, community diversity remained
significantly lower in the impact zone. Meiofauna taxa richness over the three sampling periods averaged 8 taxa/sample in the impact zone, compared to 10 taxa/
sample in the non-impact zone; and macrofauna richness averaged 25 taxa/sample
in the impact zone compared to 30 taxa/sample in the non-impact zone. Oil originating from the DWH spill had a persistent negative impact on diversity of soft-bottom,
deep-sea benthic communities. While there were signs of recovery for benthic metrics such as abundance, the low diversity and community structure differences indicate full recovery had yet to occur 4 years after the spill.
22.4 Summary and Conclusions
Oil from the DWH blowout reached the seafloor through deep-sea plumes and sedimentation of oil and oiled marine snow. This oil caused extensive damage to both
hard-bottom and soft-bottom communities. The most sensitive bioindicators to
detect the anthropogenic damage were deep-sea planar octocorals for hard-bottoms.
For soft-bottom, the most sensitive indicators were increases in polychaetes (especially those in the family Dorvilleidae), macrofauna and meiofauna diversity and
taxa richness, and the nematode/copepod ratio.
Four years after the spill, there was no recovery of the lost biodiversity of the
macrofauna and meiofauna. Ironically, abundances of macrofauna and meiofauna
can increase due to disturbance because the tolerant taxa, such as some polychaetes
and nematodes, can increase to either take advantage of the open space vacated by
sensitive taxa or by direct organic enrichment. While this response fits well into the
classic toxicity-enrichment paradox, it is evidence of disturbance and that wide
areas of the deep sea were impacted by the spill.
Both hard-bottom and soft-bottom communities appear to be very vulnerable to
deep-sea oil spills. Deep-sea corals grow slowly and thus have extremely slow
recovery rates, so it is necessary to prioritize a precautionary approach to protect
them. Results from the long-term coral monitoring study following the DWH oil
spill contributed to the recent designation of several coral sites as Habitat Areas of
Particular Concern (HAPC) in the GoM.
Future research should be focused toward recovery and restoration. For hardbottoms this could take the form of restoration projects. For soft-bottoms, the restoration strategy could be “restoration in place” because fresh sediments, which fall to
P. A. Montagna and F. Girard
The meiofauna and macrofauna community responses were re-examined again
in June 2014, approximately 4 years after the oil stopped flowing (Reucsher et al.
2017). The same 34 stations were sampled as in 2010 and 2011 from the impact
zone and the non-impact zone. Even though chemical contaminant concentrations
decreased slightly, they were still significantly different between the two zones.
PAH concentrations averaged 218 ppb in the impact zone compared to 14 ppb in the
non-impact zone. TPH concentrations averaged 1166 ppm in the impact zone compared to 102 ppm in the non-impact zone. While there was no difference between
zones for meiofauna and macrofauna abundance, community diversity remained
significantly lower in the impact zone. Meiofauna taxa richness over the three sampling periods averaged 8 taxa/sample in the impact zone, compared to 10 taxa/
sample in the non-impact zone; and macrofauna richness averaged 25 taxa/sample
in the impact zone compared to 30 taxa/sample in the non-impact zone. Oil originating from the DWH spill had a persistent negative impact on diversity of soft-bottom,
deep-sea benthic communities. While there were signs of recovery for benthic metrics such as abundance, the low diversity and community structure differences indicate full recovery had yet to occur 4 years after the spill.
22.4 Summary and Conclusions
Oil from the DWH blowout reached the seafloor through deep-sea plumes and sedimentation of oil and oiled marine snow. This oil caused extensive damage to both
hard-bottom and soft-bottom communities. The most sensitive bioindicators to
detect the anthropogenic damage were deep-sea planar octocorals for hard-bottoms.
For soft-bottom, the most sensitive indicators were increases in polychaetes (especially those in the family Dorvilleidae), macrofauna and meiofauna diversity and
taxa richness, and the nematode/copepod ratio.
Four years after the spill, there was no recovery of the lost biodiversity of the
macrofauna and meiofauna. Ironically, abundances of macrofauna and meiofauna
can increase due to disturbance because the tolerant taxa, such as some polychaetes
and nematodes, can increase to either take advantage of the open space vacated by
sensitive taxa or by direct organic enrichment. While this response fits well into the
classic toxicity-enrichment paradox, it is evidence of disturbance and that wide
areas of the deep sea were impacted by the spill.
Both hard-bottom and soft-bottom communities appear to be very vulnerable to
deep-sea oil spills. Deep-sea corals grow slowly and thus have extremely slow
recovery rates, so it is necessary to prioritize a precautionary approach to protect
them. Results from the long-term coral monitoring study following the DWH oil
spill contributed to the recent designation of several coral sites as Habitat Areas of
Particular Concern (HAPC) in the GoM.
Future research should be focused toward recovery and restoration. For hardbottoms this could take the form of restoration projects. For soft-bottoms, the restoration strategy could be “restoration in place” because fresh sediments, which fall to
P. A. Montagna and F. Girard