A study from the PLOS ONE journal reveals that pollutants in the ocean are causing wild dolphins to have weaker immune systems. The researchers studied bottlenose dolphins living off the Eastern American coast and in aquariums. Their study found that dolphins in captivity have stronger immune systems than those in the wild.
Details of the Study
According to Patricia Fair, the lead author of the study from the Medical University of South Carolina, wild dolphins are now faced with “chronically activated” immune systems because of their constant exposure to pollutants in the ocean. Wild bottlenose dolphins need to constantly fight off pathogens, parasites and anthropogenic pollutants. Their immune systems have grown weaker because there is no “balance between being able to recognise harmful organisms and over-stimulation,” says Fair. On the other hand, dolphins in aquariums are exposed to fewer pathogens since humans control the quality of their water, food and medical care.
They studied wild bottlenose dolphins off the coast of Florida and North Carolina, where the waters are exposed to industrial pollution and high levels of mercury. Researchers found that the waters close to Charleston, South Carolina have the highest levels of industrial pollution. They also discovered that dolphins living in the Indian River Lagoon in Florida had high levels of mercury in their bodies. A previous study revealed that dolphins in this area have developed a fungal skin disease as a result of new viruses and suppressed immune systems.
One co-author of the study, Dr. Gregory Bossart is a chief veterinary officer at the Georgia Aquarium. They found that the dolphins kept in the Georgia Aquarium had healthier immune systems compared to their wild counterparts. Bossart is worried for these wild dolphins because when humans face an inflammation such as “chronic immune system activation”, they become more vulnerable to infectious disease, cardiovascular disease, auto-immune disease and cancer. According to Bossart, “if wild dolphins aren’t doing well, it could also indicate future impacts to ocean health and even our own health.”
Food for Thought on Marine Pollutants
Dolphins have high levels of toxins in their bodies because of bioaccumulation. The toxins are accumulated in micro-organisms which are ingested by smaller creatures (such as fish) and when dolphins eat the fish, the organic compounds become more concentrated. Toxins increase in concentration with each step of the food chain because these animals have no way of clearing them out of their bodies. The toxins also pose health risks to humans, such as local fishermen and residents, who consume seafood and are constantly exposed to these industrial toxins.
Bossart also said, “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.” With more discoveries being made on the compromised health of marine mammals, it’s time to stop and take a look at our human impacts on the ocean. Our individual and industrial waste continue to negatively affect the Earth’s oceans and pose risks to our own health.
Dolphins are highly intelligent creatures with complex social structures and they play a key role in marine ecosystems. Now, more than ever, we need to push for changes to allow dolphin species to thrive in the wild. It would be backwards to think that captivity is the answer to enhance their immune systems, because dolphins in small tanks pose other health risks to the species. According to the Whale and Dolphin Conservation, dolphins held in captivity under human care live shorter lives than wild dolphins. So instead we must stand up for the health of our oceans and become more conscious of society’s wasteful behaviour.