Brazilian Sharpnose Sharks Found With Cocaine in Coastal Waters

Brazilian sharpnose sharks living in South America’s coastal waters have been found to carry substantial levels of cocaine and its metabolites, Brazilian researchers have reported.

Rather than resembling Hollywood portrayals of drugged-up predators on stimulant-fuelled rampages, the illicit stimulant’s impact on important species in the marine food web may be subtler, but considerably more alarming.

Cocaine in Brazilian sharpnose sharks

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

The researchers also identified considerable quantities of benzoylecgonine, cocaine’s principal metabolite, in every shark except one.

Further work will be required to establish what these results mean for the predators’ health. However, research involving other animals offers some indication of the possible consequences.

Cocaine exposure reduces cell viability and increases DNA fragmentation in zebrafish embryos. Meanwhile, a 2018 study showed that European eels experienced changes in muscle physiology when exposed to environmental concentrations of the substance.

Pharmaceutical pollution in coastal waters

Pharmaceutical contamination is a worldwide issue. Potentially more than one-quarter of the world’s waterways contain concentrations of active compounds - including ingredients found in antibiotics, synthetic oestrogen and recreational drugs - regarded as high enough to endanger ecosystems and perhaps human health.

Cocaine pollution is an especially acute concern in Brazil. Water samples taken from Santos Bay in 2017 contained cocaine at levels equivalent to caffeine, which is widely used as a benchmark for pharmaceutical pollution because it is so common in beverages worldwide.

Consumers excrete both substances, which then reach waterways through sewage. As a leading cocaine exporter, Brazil may also receive pollution from illegal drug-refining sites, as well as packages lost or abandoned by traffickers in the country’s ports.

After entering the environment, cocaine is readily absorbed by marine life lower in the food chain. It can then build up in those organisms, enabling higher-level consumers to take in greater concentrations.

Potential accumulation through the food chain

Most environmental assessments of cocaine have focused on molluscs, crustaceans and bony fish. Consequently, scientists know little about the possible health effects on major predators, particularly species that live all their lives in coastal or near-coastal waters.

Fishing vessels caught three male and 10 female Brazilian sharpnose sharks off Rio de Janeiro between September 2021 and August 2023. The animals were measured and dissected.

Scientists used liquid chromatography to test muscle and liver samples for cocaine and benzoylecgonine, its metabolic product. They found differing concentrations of the compounds, which may be linked to the sharks’ sex and reproductive condition.

Cocaine and benzoylecgonine concentrations in the sharks were up to 100 times higher than levels reported in published research for fish and other marine organisms. This supports the suggestion that cocaine may accumulate as it moves through the food chain.

The 2023 B-grade horror film Cocaine Shark offered the public a comic, though violent, vision of environmental drug contamination. In reality, the researchers are urging monitoring and awareness programmes to address a potentially much more serious issue.

Around one-third of shark and ray species face extinction, chiefly because of overfishing. Mapping and monitoring every possible threat to their populations is therefore essential.

This research was published in Science of The Total Environment.