Evidence of Gulf Corals impacted by the Deepwater Horizon oil Spill

Paul WhitbyBy Paul Whitby 7 years ago
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In the media last week there were numerous reports detailing the damage sustained by deep water corals in the Gulf of Mexico, purportedly from the spill of crude oil into the waters from the Deepwater Horizon Drilling platform.  A recent report, published by the National Academy of Sciences details the breadth of the damage.  The team, led by Charles Fisher of Penn State University, examined 11 sites hosting deep water corals within 20 km of the well approximately 3-4 months after it was capped.   The majority of these sites showed healthy corals thriving in the chill Gulf waters.  Unfortunately, the same could not be said for another site that was more directly in the path of one of the hydrocarbon rich plumes that emanated from the damaged well head.   This site was 11 km SW of the cap and 1,370 m deep.  The site itself is approximately 50x 50 m in dimension and is unusual in that there are large carbonate slabs and scattered boulders that act as attachment plates for corals to grow.  In this area are mostly gorgonians with 6 mains species being represented.  During the study, 58 colonies were identified, of which 43 were examined at close range using an ROV.  Based on the observations, the corals were ranked for health on a 0-4 scale with 0 being healthy.  Signs of impact included bare skeleton, loose tissue, heavy mucous and/or a covering of dark viscous material (floc).  The study’s results indicated that 86% of the corals in this area were impacted.  Almost 50% showed damge to over half of the actual colony at a level of 3 or 4.  In addition 23% of the corals had damage to over 90% of the colony.  On other sites 

Impacted corals observed at the affected site.  Brown material can be seen on the larger coral in both the Nov and Dec samples.  The area denoted in red is the only part showing visible growth.  Also note the pale stars on the coral.  (From the report of White et al, 2012).

  displaying healthy corals there was noted a large number of commensal ophiuroids (brittle stars) living in and among the colonies.  At the affected site, the number of stars were decreased and of those present, they were observed as being discolored and having odd posture- a sure sign of distress.  Samples of the heavy floc were taken and examined to determine the structural and chemical composition.  At first sight, it was determined that it contained dead coral polyps fragments, detached sclerites (minute, spiny skeletal elements ), and small brown droplets.  After a little forensic science, these latter components of the floc were determined to have derived from oil released from the DWH blowout.  Samples collected at other places in the gulf, where there are natural seapages showed a different chemical composition. The authors state that,” because deep-water corals are sessile and release mucous that may trap material from the water column, these corals may provide a more sensitive indicator of the impact from petroleum hydrocarbons than marine sediment cores and may record impacts from water masses passing through a community, even if no deposition to the sediment occurs”   From the corals perspective this is a serious issue as most are long lived (hundreds to possibly thousands of years) and are commonly found in areas with a good water flow.  The discovery of this site, with extensive damage and identified floc components clearly show that the oil spill from the DWH has had an impact on deep water corals.  Due to the longevity and slow pace of life at these depths, the authors conclude “it is too early to fully evaluate the footprint and long-term effects of acute and subacute exposure to potential waterborne contaminants resulting from the Deepwater Horizon oil spill”.

Categories:
  Conservation, Corals, Invertebrates, Science
Paul Whitby
About

 Paul Whitby

  (18 articles)

Paul Whitby is originally from the UK, but now resides in Oklahoma USA. While in the UK, he received his Doctorate in the microbiology of fish diseases, specifically diseases of fish with high economic importance and has published several articles in this field as well as medical microbiology. Currently he is an Associate Professor at the University of Oklahoma where he specializes in the microbiology of pediatric infectious diseases. Paul is the current President of the Central Oklahoma Marine Aquarium Society (COMAS) and has had several articles published in Reefs Magazine, Reef Keeping magazine and Reefs.com and ReefBuilders. He has published several articles on COMAS, the development of a captive propagation program to conserve coral species, pests and parasites in marine aquaria as well as numerous reviews. In October 2007 his SPS dominated display tank was selected as Reef Keeping Magazine's Tank of the Month. Paul has presented several marine aquarium related seminars at local clubs and conferences including Oklahoma's CRASE, Reef Fest, ReefStock, NERAC, IMAC west and others. In association with his good friend Ed Brookshire, Paul owns Highdefcorals.com He has been keeping saltwater aquariums for over 22 years and has owned a variety of tanks ranging from under 30 to in excess of 600 gallons. His current system, including filtration, is over 1,000 gallons.

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