Scientists have found traces of cocaine in wild sharks off the coast of Brazil.
A study from the Oswaldo Cruz Foundation found high levels of the drug in the tissue of these wild marine animals.
Researchers tested 13 Brazilian sharpnose sharks caught in the waters around Rio de Janeiro which they bought from fishers between September 2021 and August 2023.
This species, listed as vulnerable by IUCN, was selected for testing as its habitat close to the coast means it is exposed to contaminated discharges. Scientists believe Brazilian sharpnose sharks could be a sentinel species for this type of pollution.
All of the sharks tested positive for cocaine, with the drug and its main metabolite benzoylecgonine found in the muscle tissue and livers of the animals. The concentration of the drug was up to 100 times higher than previously observed in other marine life.
The study, published in the journal Science of the Total Environment, is the first to find cocaine in wild sharks. Researchers say the findings “point to the potential impacts of the presence of illicit drugs in environments”.
How did the sharks end up ingesting cocaine?
It isn’t completely clear how the cocaine ended up in the sharks.
The team told UK newspaper The Telegraph it wasn’t likely that bales of cocaine dumped overboard by smugglers were the cause of the marine animals testing positive. Not many packages of the drug are discarded or dumped in this area according to the researchers.
But drainage from the illegal labs where cocaine is manufactured and the urine or faeces of drug users are prominent sources of pollution in the water.
Wastewater treatment plants around the world are not very good at removing these substances from the water and this means they end more info up washing down into the ocean.
Regardless of where exactly it came from, cocaine only persists for a short while in the environment meaning for researchers to find it in animals like this, a lot of the drug has to be entering the ocean.
The study’s authors say cocaine consumption has increased ‘exponentially’ in the last few decades. Brazilians are among the world’s biggest consumers of cocaine and the biggest consumers of the drug in South America.
Researchers have previously found high levels of cocaine check here pollution in rivers around Rio de Janeiro. One study found that the concentration of cocaine in the waters around São Paulo was similar to the amount of caffeine found in check here coffee and tea.
What does this mean for the sharks?
Though researchers weren’t able to pinpoint any specific behavioural changes in the sharks, previous studies suggest that cocaine likely has a check here similar effect on animals as it does on humans.
Most significantly, they believe it may have an impact on their eyesight which could cause them issues when hunting. Inefficient hunting may shorten the lifespan of the sharks.
Concentrations were found to be higher in the marine animal’s muscle than in the liver and female sharks had higher concentrations than males. All female sharks in the study were pregnant but it is unclear how cocaine exposure could impact their foetuses.
Aside from the impact on the animals themselves, the sharpnose shark is a common part of the Brazilian diet. Scientists say more research is needed to assess the impact that cocaine residue could have on the people who eat them.