Sharks off the coast of the Bahamas are getting into drugs like cocaine, caffeine and painkillers — or rather, drugs are getting into them. The contaminated blood of species including nurse sharks and Caribbean reef sharks reveals the damage humans have done to paradisiac oceanic environments.
“We’re talking about a very remote island in the Bahamas,” says Natascha Wosnick, a biologist with the Federal University of Paraná in Brazil.
Wosnick is part of a team that has analyzed pollutants in sharks in the Caribbean and Brazil. In previous research, they found cocaine and rare earth elements in sharks off Rio de Janeiro.
For a new study, published in the May Environmental Pollution, the team analyzed blood from 85 sharks captured around Eleuthera Island in the Bahamas, testing for nearly two dozen legal and illegal drugs. Twenty-eight sharks from three species had caffeine, anti-inflammatory painkillers or other drugs in their blood. Some tested positive for multiple drugs. Caffeine was the most common, followed by acetaminophen and diclofenac, the active ingredients in Tylenol and Voltaren.
Most sharks were caught about four miles offshore, around an inactive fish farm popular with divers. Wosnick says currents could carry drug traces from sewage or other sources on the island, but divers are the more likely culprits. “It’s mostly because people are going there, peeing in the water and dumping their sewage in the water,” she says.
One shark — a baby lemon shark in a nursery creek — tested positive for cocaine. The amount was far lower than what researchers previously found in sharks off Brazil, but that earlier study examined muscle tissue, not blood. Because drugs persist longer in muscle, their presence in blood points to recent exposure. Wosnick says the shark may have ingested a packet containing cocaine residue; she’s seen such packages near that creek before. “They bite things to investigate and end up exposed” to substances, she says.
The team also found changes in metabolic markers in sharks with contaminated blood, including lactate and urea. It’s not clear whether the shifts are harmful, but they might impact behavior. Research in goldfish suggests caffeine increases their energy and focus, Wosnick says, much as it does in humans.
“What makes this study notable is not just the detection of pharmaceuticals and cocaine in nearshore sharks, but the associated shifts in metabolic markers,” says Tracy Fanara, an oceanographer at the University of Florida in Gainesville, who was not involved with the study. While the researchers couldn’t isolate the effects of individual drugs, contaminated sharks showed changes in markers tied to stress and metabolism.
Wosnick says the findings are concerning because the Bahamas is seen as a relatively untouched paradise. But like plastic pollution, she says, chemical pollution is more pervasive than many people realize. In the Bahamas, she adds, such pollution is often overlooked in favor of concerns like oil spills or plastic.
Fanara, who previously helped produce Cocaine Sharks, a documentary examining the possibility that sharks were encountering cocaine trafficked in the Caribbean, says that the findings are “a reminder that coastal infrastructure, tourism and marine food webs are tightly connected.”
