Births down and Deaths up in Gulf dolphins



Dolphin Y01 pushes a dead calf in March, 2013. This behavior is sometimes observed in female dolphins when their newborn calf does not survive.
Credit: Louisiana Department of Wildlife and Fisheries

Study looks at impacts of Deepwater Horizon Oil Spill (also referred to as the BP oil spill, the BP oil disaster, the Gulf of Mexico oil spill, and the Macondo blowout - More info at the end of this post)

Dolphin Y01 pushes a dead calf in March, 2013. This behavior is sometimes observed in female dolphins when their newborn calf does not survive.
Credit: Louisiana Department of Wildlife and Fisheries
Scientists are reporting a high rate of reproductive failure in dolphins exposed to oil from the Deepwater Horizon spill. The team has monitored these bottlenose dolphins in heavily oiled Barataria Bay for five years following the spill. Their findings suggest that the effects of the Deepwater Horizon oil spill will be long-lasting.

"NASA's Terra Satellites Sees Spill on May 24 Sunlight illuminated the lingering oil slick off the Mississippi Delta on May 24, 2010. The Moderate-Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image the same day.
*NOAA: National Oceanic and Atmospheric administration (USA)
A *NOAA-led team of scientists is reporting a high rate of reproductive failure in dolphins exposed to oil from the Deepwater Horizon spill. The team has monitored these bottlenose dolphins in heavily-oiled Barataria Bay for five years following the spill. Their findings, published in Proceedings of the Royal Society today, suggest that the effects of the Deepwater Horizon oil spill will be long-lasting.

The study assessed reproductive success and survival rate for Barataria Bay dolphins. These dolphins had been sampled for health assessments in 2011, and were found to have a high prevalence of lung disease and adrenal dysfunction. Now the team is reporting that only 20% of the sampled dolphins that were pregnant produced viable calves. This is compared to a previously-reported pregnancy success rate of 83% from a similar study in a dolphin population in Sarasota Bay, which was not affected by the spill.

After nearly four years of monitoring, scientists were also able to estimate the survival rate of the dolphins sampled in 2011. They found that only 86.8% of the dolphins survived each year, as compared to other populations where roughly 95% of the dolphins survived. The reduced reproductive potential, along with decreased survival, will have long-term consequences for the Barataria Bay dolphin population.

NOTE: 
The Deepwater Horizon oil spill (also referred to as the BP oil spill, the BP oil disaster, the Gulf of Mexico oil spill, and the Macondo blowout) began on 20 April 2010 in the Gulf of Mexico on the BP-owned Transocean-operated Macondo Prospect. Following the explosion and sinking of the Deepwater Horizon oil rig, a sea-floor oil gusher flowed for 87 days, until it was capped on 15 July 2010. Eleven people went missing and were never found and it is considered the largest accidental marine oil spill in the history of the petroleum industry, an estimated 8% to 31% larger in volume than the previously largest, the Ixtoc I oil spill. The US Government estimated the total discharge at 4.9 million barrels (210 million US gal; 780,000 m3).After several failed efforts to contain the flow, the well was declared sealed on 19 September 2010. Reports in early 2012 indicated the well site was still leaking.
Source: Sciencedaily