Scientists in Brazil have uncovered the first concrete evidence that sharks are being exposed to cocaine in their natural habitat. Thirteen sharpnose sharks captured from coastal waters near Rio de Janeiro tested positive for cocaine in their muscles and livers, according to a study published in Science of the Total Environment. The findings shed light on a troubling new aspect of marine pollution.
The study, led by biologist Rachel Ann Hauser Davis from Brazil’s Oswaldo Cruz Foundation, revealed significant levels of cocaine in the sharks, suggesting chronic exposure. “The key findings of the study are the presence of cocaine in sharks,” Hauser Davis said. “The actual high levels of cocaine detected in muscle is indicative of chronic exposure.”
The cocaine likely entered the ocean from contaminated wastewater in Rio de Janeiro. Narcotraffickers often discard bales of the drug during high-seas chases, which may also contribute to this environmental contamination. Despite the catchy name “Cocaine Sharks,” used in recent documentaries to highlight the issue, the evidence of drug-addled behavior among sharks remains inconclusive.
In the United States, a similar issue was highlighted in the documentary “Cocaine Sharks,” part of Discovery’s Shark Week. The documentary explored whether sharks in the Gulf of Mexico were consuming cocaine dumped by drug smugglers. Environmental engineer Tracy Fanara, who participated in the documentary, emphasized the broader problem of aquatic life being exposed to various pollutants, including recreational drugs. “Everything we use, everything we manufacture, everything we put into our bodies, ends up in our wastewater streams and natural water bodies, and these aquatic life we depend on to survive are then exposed to that,” Fanara said.
In the Florida Keys, researchers observed sharks exhibiting unusual behaviors, such as a hammerhead swimming erratically towards divers and a sandbar shark circling an imaginary object. These behaviors were noted during experiments where researchers dropped dummy bales and bait balls simulating cocaine into the water. While these observations were compelling, they were not definitive evidence of cocaine-induced behavior.
The Brazilian study, however, provides direct evidence of cocaine exposure in sharks, raising concerns about the implications for marine ecosystems and human health. Cocaine contamination in marine environments is not isolated to Brazil. A 2018 study in the United Kingdom found that eels exposed to cocaine had trouble mating, suggesting that the drug could have far-reaching effects on marine life.
Environmental experts like Anna Capaldo from the University of Naples Federico II, who did not participate in the Brazilian research, caution that cocaine pollution is an increasing danger. The impact on shark behavior and reproduction, particularly on pregnant females and their fetuses, remains an area requiring further study.
The findings have prompted calls for more extensive monitoring and testing for cocaine in coastal waters. Sharks, as apex predators, could serve as indicators of hot spots of illegal drug pollution. Given that sharks are a common food source in Brazil, high levels of contamination could pose health risks to humans as well.
Expanded Coverage:
