Deadly skin disease found in dolphins linked to climate change

TORONTO -- Scientists at The Marine Mammal Center in Sausalito, Calif. have identified a deadly skin disease in dolphins that is linked to global climate change.

In a new study published in the journal Scientific Reports, researchers found that the increasing frequency and severity of rainfall stemming from weather events such as floods, storms and cyclones has drastically decreased the salinity of coastal waters, causing a fatal skin disease in dolphins worldwide.

The disease was first noted by researchers in 2005 on approximately 40 bottlenose dolphins near New Orleans after Hurricane Katrina, but this is the first time that scientists have been able to find a direct link to the cause of the deadly skin condition.

Scientists say the dolphins develop patchy lesions across their bodies and discolouration caused by a variety of fungal and bacterial species – sometimes covering up to 70 per cent of their skin.

"This devastating skin disease has been killing dolphins since Hurricane Katrina, and we're pleased to finally define the problem," Pádraig Duignan, chief pathologist at The Marine Mammal Center said in a statement. "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."

In recent years, significant outbreaks of the condition known as “freshwater skin disease” have been identified in Louisiana, Mississippi, Alabama, Florida, Texas and Australia. Researchers say that in all of these locations, a sudden and drastic decrease in the salinity of the waters was a common factor.

Coastal dolphins are usually accustomed to seasonal changes in their marine habitat, including changes in salinity levels, however they do not live in freshwater. Scientists say that the increasing frequency and severity of storm events like hurricanes and cyclones are dumping enormous volumes of rain that are turning coastal waters into freshwater.

The freshwater conditions can last for months, particularly after intense storms such as hurricanes Harvey and Katrina.

Scientists predict that without drastic interventions to mitigate the cause of climate change, extreme storms like these will continue to occur more frequently and will result in a severe disease outbreak among dolphins.