Marine biologists are studying a deadly skin disease found on dolphins, sometimes covering up to 70% of the animal's total skin. The disease afflicts bottlenose dolphins in Louisiana, Mississippi and Alabama. Scientists have been able to relate a cause to the disorder that afflicts the disease since its appearance in 2005. In both areas, a rapid and drastic drop of salinity in seawater was the common cause.

Researchers examined about 40 bottlenose dolphins outside New Orleans which first noted the lethal skin disease in 2005 following Hurricane Katrina.

“This devastating skin disease has been killing dolphins since Hurricane Katrina, and we’re pleased to finally define the problem,” said Dr. Pádraig Duignan, Chief Pathologist at The Marine Mammal Center. “With a record hurricane season in the Gulf of Mexico this year and more intense storm systems worldwide due to climate change, we can absolutely expect to see more of these devastating outbreaks killing dolphins.”

B. A diseased Burrunan dolphin shows signs of a deadly skin disease in near Victoria, Australia. The deadly skin disease, ulcerative dermatitis,was first noted by researchers in approximately 40 bottlenose dolphins in Lake Pontchartrain, a brackishestuary near New Orleans, Louisiana, after the animals became trapped due to floodwater from Hurricane Katrina in 2005. Credit Kate Robb © Marine Mammal Foundation

This is the first time scientists have been able to relate a cause to the disorder that leads to the disease. The increasing severity and frequency of storm events like hurricanes and cyclones are dumping volumes of rain that turn coastal waters to freshwater. Climate scientists have predicted extreme storms will occur more frequently and, consequently, will result in more frequent and severe disease outbreaks in dolphins. The study comes on the heels of significant outbreaks in Louisiana, Mississippi, Alabama, Florida, Texas and Australia in recent years.

“As warming ocean temperatures impact marine mammals globally, the findings in this paper will allow better mitigation of the factors that lead disease outbreaks for coastal dolphin communities that are already under threat from habitat loss and degradation,” said Duignan. “This study helps shed light on an ever-growing concern, and we hope it is the first step in mitigating the deadly disease and marshalling the ocean community to further fight climate change.”

This research has major consequences for Australia's ongoing epidemic, which affects the endangered and threatened Burrunan dolphin in Southeast Australia, which will provide clinicians with the knowledge they need to identify and treat infected species. The long-term outlook for skin disease-affected dolphins is currently low. This is particularly true for animals with extended freshwater exposure.

C. A closeup view of Burrunan dolphin shows signs of skin lesions associated with a deadly skin disease known as ulcerative dermatitis. Scientists at The Marine Mammal Center and international colleagues noted thatoutbreaks of the disease have occurred in in Louisiana, Mississippi, Alabama, Florida and Texas and Australia in recent years and will continue to emerge where coastal dolphin communities globally are exposed to sudden or unprecedented environmental change as a result of climate change. Credit Kate Robb © Marine Mammal Foundation

Cover photo: D. Scientists measure the visible skin lesions on a diseased Indo-Pacific dolphin. Scientists found that the sudden drop in a waterway’s salinity levels after a hurricane coupled with a period of low salinity levels can last in an impacted area for months. Currently, the long-term outlook for dolphins affected with the skin disease is poor. This is especially true for the animals suffering from prolonged exposure to freshwater. Credit Nahiid Stephens © Murdoch University