Dolphin Skin Lesions from Freshwater Exposure
A bottlenose dolphin with skin lesions caused by prolonged freshwater exposure. NMFS Permit # 14450 Credit: NOAA

A new study says a proposed environmental project to restore coastal marshes in Louisiana's Barataria Bay will cause the population of bottlenose dolphins living in those waters to become functionally extinct, according to a team of scientists at the National Marine Mammal Foundation (NMMF),  University of St Andrews and others. The findings come on the 12th anniversary of the Deepwater Horizon oil spill, which continues to adversely affect the health of dolphins in the northern Gulf of Mexico.

The Mid-Barataria Sediment Diversion is a project proposed by the Coastal Protection and Restoration Authority of Louisiana in an attempt to restore coastal marshes and reduce land loss by diverting sediment from the Mississippi River into the Barataria Basin. The $2 billion project could get government approval early next year. Marine mammal scientists say the project would be disastrous for a dolphin population still recovering from the oil spill.

"We've been monitoring the health of dolphins in this area for more than 10 years since the DWH spill. While the animals continue to face lower birth rates and chronic respiratory problems, our research shows this project would not only hinder recovery, but would potentially lead to the deaths of thousands of dolphins," said Dr. Lori Schwacke, NMMF's Chief Scientist for Conservation Medicine and one of the study's co-authors.

Dr. Len Thomas, the lead author of the study, added, "Simply put, our research predicts the project would cause a decline of at least 97 percent in the population of just over 2,000 dolphins."

Scientists say the influx of fresh water created by the diversion project will result in decreased levels of salinity in the basin. Prolonged exposure to low salinity has been linked to skin lesions and other diseases in dolphins that can result in death.

"Our research builds on the modeling conducted for the project's Environmental Impact Statement and quantifies the likely drastic impacts for the population from one year to the planned 50 years of operation of the diversion," said Dr. Ryan Takeshita, NMMF's Deputy Director of Conservation Medicine and co-author. "The declines are predicted to be far greater than those caused by the DWH oil spill." 

The DWH explosion caused a devastating flow of more than 130 million gallons of oil into the Gulf over an 87-day period.

A decade of research indicates that the health of dolphins and other marine mammals in the Gulf of Mexico is not improving, and in some cases may be worsening. Dolphins exposed to the DWH oil continue to battle chronic, and potentially progressive, lung disease. This is consistent with human health studies, which have reported an increase in respiratory symptoms among individuals who responded to the oil spill. Contact steve.walker@nmmf.org