Cocaine Found in Brazilian Sharpnose Sharks off South America

Brazilian sharpnose sharks inhabiting South America’s coastal waters carry substantial concentrations of cocaine and its metabolites, a Brazilian research team has reported.

Rather than the Hollywood image of drug-addled predators embarking on cocaine-fuelled frenzies, the illegal stimulant’s impact on important links in the marine food web may be subtler – and considerably more alarming.

The researchers, headed by environmental scientist Gapriel de Farias Araujo of Brazil’s Oswaldo Cruz Institute, detected elevated cocaine concentrations in all 13 juvenile and young adult Brazilian sharpnose sharks (Rhizoprionodon lalandii) examined.

The primary cocaine metabolite, benzoylecgonine, was likewise present in considerable quantities in every shark except one.

Cocaine in Brazilian sharpnose sharks

Further investigation will be required to establish what these results mean for the predators’ health. However, research involving other animals offers indications of possible effects.

When zebrafish embryos are exposed to cocaine, their cells show reduced viability and greater DNA fragmentation. Meanwhile, a 2018 study reported that European eels experienced changes to muscle physiology when exposed to environmentally relevant concentrations of the drug.

Pharmaceutical contamination is a worldwide concern. Potentially more than one-quarter of global waterways contain concentrations of active substances – including ingredients found in antibiotics, synthetic oestrogen and recreational drugs – deemed high enough to endanger ecosystems and perhaps human health as well.

Brazil has an especially severe cocaine pollution issue. Water samples taken from Santos Bay in 2017, for example, contained cocaine at levels matching those of caffeine. Caffeine is widely used as a benchmark for pharmaceutical pollution because it is prevalent in beverages across the world.

Consumers excrete both substances, which then reach waterways through sewage. As a leading cocaine exporter, Brazil may also face contamination from illicit refining sites, while packages lost or thrown away by traffickers at the country’s ports could add to the problem.

How cocaine enters the marine food chain

After entering the environment, cocaine is readily taken up by marine life at the lower levels of the food chain. It can then build up in those organisms, enabling higher-order consumers to absorb it at greater concentrations.

Environmental assessments of cocaine have largely focused on molluscs, crustaceans and bony fish. Consequently, scientists know little about its possible health effects on major predators, particularly species that live all their lives in coastal waters or nearby.

Fishing vessels caught three male and ten female Brazilian sharpnose sharks off Rio de Janeiro between September 2021 and August 2023. The animals were then measured and dissected.

Researchers used liquid chromatography to analyse samples of muscle and liver tissue for cocaine and its metabolised product, benzoylecgonine. The tests identified differing concentrations of both compounds, potentially linked to variation in the sharks’ sex and reproductive condition.

The concentrations of both cocaine and benzoylecgonine in these sharks were up to a hundred times higher than levels recorded in published research on fish and other marine organisms. This finding supports the suggestion that cocaine may accumulate as it moves through the food chain.

Monitoring a potentially serious threat

The 2023 B-grade horror film Cocaine Shark offered the public a comic, albeit violent, depiction of environmental drug pollution. In contrast, the researchers are urging surveillance and awareness programmes to address what could be a much more serious real-world issue.

Around one-third of shark and ray species are threatened with extinction, chiefly because of overfishing. It is therefore essential to identify and monitor every possible danger to their populations.

The research was published in Science of The Total Environment.