The first study comparing the health of wild and captive dolphins found that the captives ones are much healthier. Wild dolphins are suffering greatly due to pollution, and are starting to carry diseases which could affect even humans.

Dolphins aren’t doing so well, and this is an alarm signal for all of us. Image credits: NASA.

When it comes to protecting the planet, we focus almost all our efforts on land even though most of it is covered by seas and oceans. The reasoning is pretty simple: we live on land, we don’t really see what’s happening in the water — even though scientists have a pretty good idea about the general in’s and out’s of the oceans, it’s hard to empathize in the same way. To put it bluntly, we don’t really care about the oceans, not as much as we should. For the most part, humanity has treated the oceans like a big sink (for carbon, plastic, and junk in general), and it’s starting to show.

As predators pretty high up the food chain, they tend to accumulate the pollution from all the ranks below them. Things get polluted, fish eat said things, and dolphins eat said fish, sucking all the pollution within. This is a general rule in ecosystems, predators tend to concentrate pollution — which is one of the reasons researchers wanted to study dolphins. Another couple of reasons is that they are mammals and they’re more similar to humans than the average fish, and we’ve been keeping them in captivity for long enough to conduct a relevant comparison.

Patricia Fair, a research professor at the Medical University of South Carolina and lead author of the study, says the immune systems of all wild dolphins they studied were “chronically activated” due to the unhealthy environments they were living in.

“This is likely a result of encountering and fighting off illness caused by pathogens, parasites and anthropogenic pollutants in the ocean that do not exist in closely managed zoological habitats,” she explained. “The key to a healthy immune system is a balance between being able to recognise harmful organisms and over-stimulation and this study demonstrates the importance of the environment in these responses.”

They focused their study on the coasts of Florida and South Carolina. Noticeably, dolphins living nearby the Indian River Lagoon in Florida were found with larger amounts of mercury inside, which is also worrying for humans in the area — who can accumulate mercury in a similar way. But that wasn’t even the worst area; dolphins living in the ocean near Charleston, South Carolina exhibited the worst symptoms.

“In humans, this type of prolonged smouldering inflammation is associated with cancer, auto immune disease, cardiovascular disease, and increased vulnerability to infectious disease,” he said.

Due to the environmental stress, the dolphins are also vulnerable to diseases. Previous studies have shown that a fungal skin disease is running rampant in populations of dolphins with suppressed immune systems, which could be potentially passed on to humans. Having a fungal and microbial flora is absolutely normal in all environments, but generally, the immune system of higher animals should be able to keep them under control — when this doesn’t happen, it’s a sign that they’re in trouble.

Doctor Gregory Bossart, a co-author of the study and chief veterinary officer at Georgia Aquarum, said that the implications of these chronic problems should not be underestimated, and commented on the severity of the response we are seeing.

“In humans, this type of prolonged smouldering inflammation is associated with cancer, autoimmune disease, cardiovascular disease, and increased vulnerability to infectious disease.”

He also warned that dolphins are a sentinel species, serving as a marker for the overall health of the oceans. At the moment, things are not looking good.

“These wild dolphins are trying to tell us something and we are not listening. As a sentinel species, dolphins are an important way to gauge the overall health of our oceans. If wild dolphins aren’t doing well, it could also indicate future impacts to ocean health and even our own health.”

Journal Reference: Patricia A. Fair , Adam M. Schaefer, Dorian S. Houser, Gregory D. Bossart, Tracy A. Romano, Cory D. Champagne, Jeffrey L. Stott, Charles D. Rice, Natasha White, John S. Reif — The environment as a driver of immune and endocrine responses in dolphins (Tursiops truncatus). https://doi.org/10.1371/journal.pone.0176202