High Number of Gulf Dolphin Deaths Caused by Deepwater Horizon Spill

One month to the day after commemorating the 5-year anniversary of the BP Deepwater Horizon oil disaster, the US National Oceanic and Atmospheric Administration (NOAA) published results of a new study pointing to dolphin injury from the spill.

Since 2010, there has been an unusually high number of dolphin deaths in the northern Mexican Gulf, the most severe dolphin die-off ever recorded in the region.

As part of the mortality event investigation, a team of scientists has discovered that dead bottlenose dolphins stranded in the northern Gulf of Mexico since the start of the Deepwater Horizon oil spill have lung and adrenal lesions consistent with petroleum product exposure, according to NOAA’s study.

These findings support those of a 2011 health assessment of live dolphins in Barataria Bay, Louisiana, a heavily oiled area during the spill which showed those resident dolphins had poor health, adrenal disease, and lung disease.

The timing, location, and nature of the detected lesions support that contaminants from the Deepwater Horizon oil spill caused these lesions and contributed to the high numbers of dolphin deaths within this oil spill’s footprint, the study shows.

“This is the latest in a series of peer-reviewed scientific studies, conducted over the five years since the spill, looking at possible reasons for the historically high number of dolphin deaths that have occurred within the footprint of the Deepwater Horizon spill,” said Dr. Teri Rowles, veterinarian and one of 22 contributing authors on the paper, and head of NOAA’s Marine Mammal Health and Stranding Response Program.

“These studies have increasingly pointed to the presence of petroleum hydrocarbons as being the most significant cause of the illnesses and deaths plaguing the Gulf’s dolphin population. This study carries those findings significantly forward.”

Dolphin Deaths Caused by Deepwater Horizon Spill1

Direct causes of death, during this period, likely included:

  • Chronic adrenal insufficiency resulting from adrenal gland effects;

  • Increased susceptibility to life-threatening outcomes due to adrenal insufficiency, especially when challenged with pregnancy, cold temperatures, and infections; and

  • Increased susceptibility to primary bacterial pneumonia, possibly due to lung injury, or alterations in immune function.

“The new study released by NOAA should remind us that the BP oil disaster will have a continued impact on the Gulf of Mexico and the species who call it home. The question remains to what extent? We must remain vigilant and monitor the Gulf ecosystem in order to guide restoration where it is most needed and be able to track recovery.

These new findings should be a resounding reminder to our Gulf leaders that restoration dollars should be spent on restoring the invaluable natural resources of the Gulf of Mexico,” commented Kara Lankford, Associate Director of Ocean Conservancy’s Gulf Restoration Program.

Images: NOAA, Ocean Conservancy