Two years ago, Cocaine Bear hit theaters with a science fiction-like plot. In essence, it was about a bear on cocaine. The story was fantastic but also entirely real: The bear had ingested four grams before dying, along with a lost shipment. The truth is that there have been several animals with traces of drugs, but none like the case in Brazil. Researchers analyzed 13 sharks for cocaine, and they all tested positive.
The study. Brazilian researchers recently published their work in Science of the Total Environment journal. The team caught 13 sharks—a relatively small species, about 3 feet long—off the coast of Rio de Janeiro that feeds mainly on small fish and squid.
After capturing them, researchers took samples of the sharks’ muscles and livers and analyzed them for signs of drugs and related chemicals. The results alarmed the scientists: All the sharks tested positive for cocaine. But not only that, 12 of the 13 had benzoylecgonine in their system, a chemical produced when cocaine leaches through the liver and into the body.
The sewage problem. To understand this study, we need to go back in time. Cocaine, like other drugs, enters the oceans through a variety of routes, including sewage spills and lost packages from drug traffickers that end up in the water and are ingested by marine animals (as in the case of the bear).
Scientists know this because, through these processes, they’ve detected traces of cocaine in sewage and surface water in at least 37 countries between 2011 and 2017. In addition, the drug has also ended up in the bodies of various forms of aquatic life, including mollusks, crustaceans, and bony fish. However, no one had ever done a similar study with sharks and the drug as the protagonists.
Sharks on drugs. According to the team, the finding is due to a combination of increasing cocaine consumption (especially in Brazil), inadequate wastewater treatment, runoff from cocaine production, and drug packages floating in the water.
Here’s where the 13 Brazilian sharpnose sharks (Rhizoprionodon leylandii) analyzed appear, caught by fishermen off the coast of the southeastern state of Rio de Janeiro. The marine biologists chose this species because it spends its entire life in coastal habitats and is, therefore, likely to have been exposed to human pollution.
Drug testing. The team measured the weight and length of each shark before dissecting it. Then, the Brazilian researchers took muscle and liver samples for testing. The results were unequivocal: The tests revealed that every sample from the sharks tested positive for cocaine. In addition, 92% of the muscle and 23% of the liver samples also tested positive for one of the drug’s primary metabolites, benzoylecgonine. This is the first evidence of cocaine in wild sharks.
Effects on the marine environment. Although the research doesn’t indicate whether cocaine exposure significantly affects sharks, research on its impact on other fish, such as eels and zebrafish, has found differences in critical proteins, skin changes, and changes in hormone function. Therefore, the team believes that exposure to the drug could cause severe damage to sharks’ health, including damaging their DNA, affecting their ability to metabolize fats, or causing behavioral changes.
They do make clear that this finding is a significant warning. More tests are necessary in the short term. “We recommend the expansion of environmental monitoring studies related to the drugs on the Brazilian coast, as well as a detailed investigation of their effects on environmental health and associated risks," they wrote.
Cocaine in sharks is also bad for humans. In addition, the study also suggests that finding sharks with cocaine in their bodies can lead to problems for humans. Experts say that “the findings indicate potential risks to human health, given the high consumption of sharks in Rio de Janeiro throughout Brazil and the world.”
It’s not good news that we’ve found sharks in the wild with traces of cocaine for the first time: “Given the psychotropic effects of drugs in vertebrates, behavioral changes may occur that, although sublethal, could affect the survival of the species in ways that have not yet been explored,” the researchers conclude.
This article was written by Miguel Jorge and originally published in Spanish on Xataka.
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