[OANNES Foro] Oil spill linked to Gulf of Mexico dolphin deaths

[Mario Cabrejos]

Animals suffered from adrenal and lung problems that are consistent with
exposure to petroleum.

Deepwater Horizon oil spill linked to Gulf of Mexico dolphin deaths

 
<http://www.nature.com/news/deepwater-horizon-oil-spill-linked-to-gulf-of-me
xico-dolphin-deaths-1.17609?WT.ec_id=NEWS-20150521#auth-1> Allie Wilkinson

Nature doi:10.1038/nature.2015.17609 20 May 2015

http://www.nature.com/news/deepwater-horizon-oil-spill-linked-to-gulf-of-mex
ico-dolphin-deaths-1.17609?WT.ec_id=NEWS-20150521

 

More than 1,300 bottlenose dolphins have stranded themselves in the northern
Gulf of Mexico since early 2010. Research now links this unusual mortality
event to the massive Deepwater Horizon oil spill.

The spike in dolphin deaths began shortly before the spill in April 2010,
and scientists have struggled to understand whether the two events are
related. A study published on 20 May in PLoS ONE finds that many of the dead
animals had lung and adrenal-gland lesions that are consistent with exposure
to petroleum compounds
<http://www.nature.com/news/deepwater-horizon-oil-spill-linked-to-gulf-of-me
xico-dolphin-deaths-1.17609?WT.ec_id=NEWS-20150521#b1> 1.

That led the study's authors to conclude that the Deepwater Horizon spill
probably drove the mass deaths. The study builds on a 2011 assessment of
live dolphins in Barataria Bay, Louisiana, that
<http://www.nature.com/doifinder/10.1038/nature.2012.11011> revealed
widespread adrenal and lung disease and general poor health
<http://www.nature.com/news/deepwater-horizon-oil-spill-linked-to-gulf-of-me
xico-dolphin-deaths-1.17609?WT.ec_id=NEWS-20150521#b2> 2. The spill, which
began with the explosion of a BP drilling rig, caused heavy and prolonged
oiling in the bay.

In the latest study, researchers analysed lung and adrenal-gland tissue
samples from 46 dolphins that were found dead in Louisiana, Mississippi and
Alabama - areas that experienced significantly elevated levels of petroleum
compounds. The team compared these animals with a reference group of 106
dolphins that stranded before the mass deaths began, or outside of the area
where these strandings took place.

The dolphins that died in the footprint of the Deepwater Horizon oil spill
were more likely to have lesions in their lungs and adrenal glands than
animals from outside that area were, says Kathleen Colegrove, one of the
study's authors and a veterinary pathologist at the University of Illinois
at Urbana-Champaign.


Catastrophic colds


Other differences were also apparent. More than one in five dolphins from
the mass-death group had bacterial pneumonia, and the disease caused or
contributed significantly to the deaths of 70% of these animals. In
contrast, just 2% of the animals in the reference group had pneumonia.

"What's been really striking to me as a pathologist has been the severity of
some of these pneumonias," Colegrove says. "They've been some of the most
severe pneumonias that myself or some of the other pathologists involved in
this investigation have ever seen."

Dolphins in the Deepwater Horizon footprint were also more likely to have a
thin adrenal cortex, which can increase the risk of death and disease -
especially in animals that are already fighting infection, exposed to cold
temperatures or are pregnant. The condition was observed in a third of the
animals from the mass-death group, including half of the dolphins from
Barataria Bay.

"Animals with untreated adrenal dysfunction can essentially be balancing
precariously on a ledge, waiting for the right stressor to push them into an
adrenal crisis, including rapid death from shock," says Stephanie
Venn-Watson, a veterinary epidemiologist at the National Marine Mammal
Foundation in San Diego, California, and the study's lead author.


Oil trigger


These results, taken with the findings of the 2011 assessment, show that
dolphins were significantly affected by exposure to petroleum compounds
after the Deepwater Horizon spill, Colegrove says. That exposure caused the
animals' adrenal and lung disease, and those conditions were major factors
in increasing dolphin deaths, she adds.

Frances Gulland, a veterinarian at the Marine Mammal Center in Sausalito,
California, is pleased to see concrete data on the potential impacts of the
spill after years of debate. "It's really nice to see real confirmation from
histology," she says.

But the book is not closed on the dolphin deaths. Because the animals are
long-lived, and slow to mature and reproduce, Colegrove says that it will be
many years before scientists understand the full effects of the Deepwater
Horizon spill on the Gulf of Mexico population.

In a prepared statement, BP spokesman Geoff Morrell disputed any connection
between the oil spill and the dolphin deaths. "The data we have seen thus
far, including the new study from [the US National Oceanic and Atmospheric
Administration], do not show that oil from the Deepwater Horizon accident
caused an increase in dolphin mortality," he said.


 <javascript:;> References


o    Venn-Watson, S. et al. PLoS ONE 10, e0126538 (2015).
<http://dx.doi.org/10.1371/journal.pone.0126538> Article
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=P
ubMed&list_uids=25992681&dopt=Abstract> PubMed  <javascript:;> Show context

o    Carmichael, R. H., Graham, W. M., Aven, A., Worthy, G. & Howden, S.
PLoS ONE 7, e41155 (2012).  <http://dx.doi.org/10.1371/journal.pone.0041155>
Article
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=P
ubMed&list_uids=22815950&dopt=Abstract> PubMed
<http://chemport.cas.org/cgi-bin/sdcgi?APP=ftslink&action=reflink&origin=npg
&version=1.0&coi=1:CAS:528:DC%2BC38XhtV2msLnK&pissn=0028-0836&md5=7a891410df
d14cb9cbeb558ea34ae019> ChemPort  <javascript:;> Show context

 



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